_ .‘ 4a.: luff:\\'4‘1i \x.‘. »' w~ us _... u -L-.. . :’ 3.-..Nt. _ 1 ~ u“.;_..- .H'“ "v --‘ - -« ..:: 2‘. _ II. V .n‘ .r 4“ .O «NP l r V. T’m .13: “ZN. 1. - 5-1». nu IBRARIES IIIII‘III IIIIII \II‘IIIIIIII 31293 This is to certify that the dissertation entitled THE EFFECTS OF EXERCISE TRAINING AND SEVERE CALORIC RESTRICTION ON LEAN-BODY MASS IN THE OBESE presented by Brian C. Leutholtz has been accepted towards fulfillment of the requirements for Ph.D. degreein the Department of Physical Education and Exercise Science :24z/(flL‘V [5/ flarxaw Major professor Date October 30, 1991 MSU i: an Affirmative Action /Equal Opportunity Institution 0-1277l LIBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MSU is An Affirmative Action/Equal Opportunity Institution chS—nt THE EFFECTS OF EXERCISE TRAINING AND SEVERE CALORIC RESTRICTION ON LEAN-BODY MASS IN THE OBESE By Brian Carlton Leutholtz A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Physical Education and Exercise Science 1991 ABSTRACT THE EFFECT OF EXERCISE TRAINING AND SEVERE CALORIC RESTRICTION ON LEAN-BODY MASS IN THE OBESE. By Brian C. Leutholtz The purpose of this study was to investigate the effects of exercise intensity on the body composition of obese subjects during severe caloric restriction. Forty obese subjects (33 women, 7 men; 41 i 7.7 years; 106 i 26 kg; body fat > 25% men, > 30% women) on a commercially prepared, 420 Kcal/day, supplemented fast were randomized into groups that exercised at 40% and 60% of the heart rate reserve (HRR). Training volume was similar for both groups, at approximately 300 Kcal/day, three days per week for 12 weeks. Body weight (BW), body fat (BF) and lean weight (LN) were similar for both exercise intensity groups at week one. Overall, body weight decreased by 15.3 i 6.7 kg (p<.OS), and body fat decreased by 14.9 i 5.0 kg (p<.05) for the 40 subjects, while lean weight remained unchanged. No significant differences in body weight, body fat or lean weight were observed between the two groups. Gain scores in body weight, body fat Group 40% (n-20) 60% (n-20) The results Brian Carlton Leutholtz and lean weight follow for each group: Lita grits). LEM -15.0 i 8.4 -13.8 i 5.2 -1.2 i 3.3 -15.7 i 5.3 -15.9 i 4.9 +0.20 i 2.1 of the current study showed that, while on a supplemented 420-Kcal/day fast, exercise at 40% and 60% of the HRR affected body composition similarly when total training volume was held constant at 900 Real/week. Lean weight remained unchanged and accompanied a 14. 9 i 5.0 kg decrease in body fat. These results suggest that exercising at 60% of the HRR offers no advantages for body composition changes over those obtained from exercising at 40% of HRR. DEDICATION To my Mother and in memory of my Father iv ACKNOWLEDGMENTS I wish to thank Dr. William Heusner and Dr. Randall E. Keyser for their advice and guidance in the preparation of this study. I wish also to thank Dr. Lonnie Rosen and Dr. Vernon Wendt for their assistance on the doctoral committee. Acknowledgment is also made of the understanding and encouragement rendered by the Cardiac Rehabilitation Staff of Butterworth Hospital, Grand Rapids, Michigan. TABLE OF CONTENTS CHAPTER ' PAGE LIST OF TABLES ......................................... viii I. INTRODUCTION ...................................... 1 Statement of the Problem .......................... 4 Research Hypotheses ............................... 4 Research Plan ..................................... 4 Rationale for the Research Plan ................... 6 Significance of the Problem ....................... 7 Limitations of the Study .......................... 7 II. REVIEW OF RELATED LITERATURE ...................... lO Obesity Risks and Hazards ......................... 12 Exercise Retention of Lean-Body Mass .............. 14 Exercise and Metabolic Rate ....................... 19 Body Composition Using Bioelectrical Impedance ....................................... 22 Summary ........................................... 24 III. METHODS AND MATERIALS ............................. 26 Subjects .......................................... 27 Adherence to the Exercise Program ................. 27 Training Procedures ............................... 28 Instruments ....................................... 29 Measurement Procedures ............................ 29 Analysis of Data .................................. 31 IV. RESULTS AND DISCUSSION ............................ 32 Demographics ...................................... 32 Body Composition Results .......................... 34 Exercise Results .................................. 34 Adherence Results ................................. 4O TABLE OF CONTENTS -- CONTINUED IV. Discussion ........................................ Body Composition ............... ’ ................... Exercise Training ................................. V. SUMMARY CONCLUSIONS AND RECOMMENDATIONS ........... Conclusions ....................................... Recommendations ................................... REFERENCES .................................................. A. EXERCISE LOG WALKING PROGRAM ...................... B. OBESITY AND ASSOCIATED CONDITIONS ................. C. MEDICAL RESTRICTIONS .............................. D. CONSENT FORM ...................................... E. NUTRIENT BREAKDOWN OF OPTIPAST 7O ................. F. EXERCISE PRESCRIPTION METHODS ..................... G. BRUCE PROTOCOL .................................... vii 4O 45 49 51 52 52 54 66 67 68 69 71 73 74 TABLE 10. Demographics. LIST OF TABLES oooooooooooooooooooooooooooooooooooooo Body Composition: Data Independent of Groups ....... Between-Group Results for Between-Group Results for Between-Group Gain Scores Variability: Body Composition Week 1 ............................... Variability: Body Composition Week 12 .............................. Variability: Body Composition oooooooooooooooooooooooooooooooooooooo Exercise Training: Data Independent of Groups ...... Between-Group Results for Between-Group Results for Between-Group Gain Scores Between-Group Variability: Exercise Training Week 1 ............................... Variability: Exercise Training Week 12 .............................. Variability: Exercise Training oooooooooooooooooooooooooooooooooooooo Variability: Adherence Results ....... viii 33 35 36 37 38 39 41 42 43 44 CHAPTER I THE PROBLEM It has been estimated that 80% of American women diet each year (3). Children as young as nine years of age are on persistent diets. These patterns of behavior may be related to the emphasis that society places on a lean appearance. There are no universally accepted standards by which obesity is either defined or measured. Obesity sometimes has been defined in terms of the Body Mass Index (BMI) which is the quotient of (weight in kg divided by height in m2). When BMI is greater than 25 to 30, subjects generally are regarded as obese (77, 102). However, BMI does not account for lean-body weight. One may argue that subjects who resistance train may have a BMI values greater than 30 without being obese due to increased muscle mass. Another method frequently used to assess obesity is visual determination based on a perception of body fatness. However, visual determination is more subjective than other methods and makes obesity difficult to categorize. Garrow (47) recommended that obesity be defined as a body weight greater than approximately 22% body fat for men and 28% body fat for women. '8 A measured fat of 25% or more for men and 30% or more for women also has been used to identify obesity (3, 29). An ideal fat percentage has not been established; however, many agree that desired values range between 16% and 25% for women and are less than 20% for men (22). A universal value representing the optimal body fat level .for each gender is not available because body composition may change with may factors including age. Women normally have higher body fat percentages than men. Body fat percentages of more than 25% for men and more than 30% for women apparently represent high values at any age and classify 15% of the adult population as obese (3, 138). Talbot (121) reported that 4.9% of men and 7.2% of women between the ages of 20 and 74 years are obese. Even these relatively conservative estimates suggest that there are between five and ten million obese adults in the United States. Furthermore, at the 1985 NIH Consensus Conference on Health Risks of Obesity, body fat resulting in a person being more than 20% over ideal body weight, as measured from the Metropolitan weight tables, was reported as the point at which health risks such as hypertension, atherosclerosis, diabetes mellitus, osteoarthritis and reduced myocardial function increase (3). Studies measuring body composition changes resulting from weight- loss during various exercise regimens and caloric restrictions have produced a range of results (19, 54). Hagan et a1. (54) found no significant changes in body weight in subjects who aerobically exercised 5 days/week for 12 weeks at 60 % of maximum heart rate without dietary modifications. Pavlou et al. (102) reported that exercising aerobically three days/week at 70% to 85% of maximum heart rate during an eight-week weight-loss program based upon a daily dietary intake of only 800 Kcal/day, spared the loss of lean-body weight and produced a greater loss of body fat than did caloric restriction alone. Findings such as these lend support to the concept that the addition of regular exercise to a caloric-deficient diet minimizes the loss of lean-body weight (54). Conflicting reports may be due to lower exercise intensities, short study durations and varying contents of the hypocaloric diets (19, 54). Langman and Schteingart (44) suggest that it is not clear what physical training contributes when diet and exercise are combined. Other investigators such as Brownell (23) agree that the alteration of lean-body mass is an important area for further study. Many investigators have failed to determine the energy cost of activity which makes it difficult to compare and explain confliczing data. Controversies regarding metabolic rate following diet and/or exercise may be the result of failure to account for factors such as variations in the exercise regimen (intensity, duration, amount and mode), body composition, subject diet, and baseline energy expenditure (19). However, it is known that lean-body mass is metabolically active tissue that expends approximately 50 calories per pound (5). Furthermore, it has been suggested that adding exercise to a hypocaloric diet may minimize or prevent this drop in resting metabolic rate, although conclusive data in humans still are lacking (112). Even if exercise finally is confirmed to be beneficial to those on diets, there still are uncertainties related to the optimal amount of exercise needed to spare lean-body mass and thus to minimize the reduction in resting metabolic rate. Statement 91 the Emblem The purpose of this study was to compare the effects of high- intensity and low-intensity exercise regimens on changes in the lean tissue of morbidly obese subjects during a 12-week period of severe caloric restriction. Research Hypotheses After careful review of literature, the current investigation was designed to test the following two research hypotheses: l. Aerobic exercise will help to preserve lean-body mass in obese subjects during a weight-loss period of severe caloric restrictions. 2. When total caloric expenditure is held constant, greater retention of lean-body mass will occur with a program of high-intensity exercise than with a program of low-intensity exercise. Research Plan The current study involved two levels of exercise intensities. Subjects in the high-intensity group exercised at 60% of their heart rate reserve (HRR), while subjects in the low—intensity group exercised at 40% of their heart rate reserve (HRR). The frequency of the exercise sessions was three times per week, with subjects in both groups expending 300 Kcals per session. The duration of the study was 12 weeks and was concomitant with a 12-week supplemented fasting regimen. The supplemented fast consisted of a daily intake of 70 grams of protein, 30 grams of carbohydrate and 2 grams of fat. The mode of exercise was walking. Exercise prescriptions were determined using the "Bruce" treadmill protocol and a metabolic cart (2001 Medical Graphics). Forty obese subjects (33 women and 7 men) were stratified by gender and then assigned randomly to the two exercise groups. The subjects were tested at the beginning and again at the end of the treatment period for body weight. In addition, body fat and lean-body mass were measured using bioelectrical impedance (RJL Systems, Model Za-180-57). Peak oxygen uptake, heart rate systolic blood pressure, diastolic blood presure and treadmill time were determined during the Bruce protocol which was administered in the first and last weeks of the study. Exercise adherence was encouraged by the use of contracting and verification by a significant other. The subjects kept exercise logs which were monitored weekly. Appropriate t-test, Chi-square test, and analysis of variance statistical methods were used to evaluate the results which were expressed both as raw scores and as gain scores. Rationale for the Research Elan Exercise prescriptions for obese individuals should emphasize caloric expenditure, and exercise intensity should be prescribed at a level that will minimize the risk of orthopedic problems and facilitate compliance (4). The intensity of exercise for individuals who are at their ideal weight often is prescribed at 60% to 85% of the HRR (4). Exercise intensity for obese individuals usually is more conservative, around 50% of the subjects functional capacity or about 60% of the HRR. Leutholtz and Keyser (81) compared 60% of the HRR in obese subjects to their measured peak heart rates. It was concluded that 40% of the subjects tested would have been exercising at 93% of their age predicted measured peak heart rates when exercise was prescribed at 60% of the HRR. The resulting intensity level could increase the risk of injury and compromise compliance. The current study tested a "window" of exercise intensity, set at 40% and 60% of the measured heart rate reserve, to determine the effects of differences in exercise intensity on lean tissue retention when obese subjects are placed on a controlled, supplemented, fasting regimen. Foss, et a1. (42) stated that knowledge of individual patient variability is important in the formulation of precise exercise prescriptions for obese patients as well as for defining realistic goals and expectations of their progress. Specific guidelines regarding exercise prescriptions for obese individuals currently are not available. Significahce 9f ghg Problem Assuming that lean-body mass retention will cause the resting metabolic rate to remain elevated during and after caloric restriction, the more lean tissue that can be retained following weight-loss the higher the metabolism (53, 56, 62). This relationship may be an essential factor in maintaining the ideal body weight after the cessation of a strict diet. Hypocaloric diets have been followed by 70% to 100% participant recidivism, and subsequent weight gains often have resulted in final weights being even greater than initial weights (66, 93, 119, 127). Participants may be faced not only with an increase in their body weight from initial values, but with a concomitant rise in adipose tissue and a decrease in lean tissue. Limitations hf ghg Sghgy 1. Due to the distances most subjects were required to travel, a single suitable location could not be found. Work schedules interfered with the ability of most subjects to return to a central location during the daytime. Equipment availability also was a problem. A site with lOIto 15 treadmills was not available, and scheduling subjects into groups of four or five at various class times was impossible due to both time restraints and lack of personnel. Therefore, individualized conditioning programs had to be used. An attempt to achieve accountability was made by requiring a significant other to sign each subject's weekly exercise log (lll) (appendix A). Responsibility for completion of the exercise log remained with the subject. The subjects received one hour of structured lecture on exercise compliance four times during the lZ-week experimental period, and they were contacted personally each week to ensure that they were monitoring their pulses and were exercising at the proper intensity whenever weekly logs were not received. Due to the cost of the weight loss program ($150.00/week), subject eagerness and exercise adherence appeared to remain high. 2. Due to time restraints, it was not possible to schedule all subjects and test them on the same day. The laboratory is used by other departments, and tests are scheduled months in advance. Consequently, subject pre-training and post-training testing was done throughout the first week and again throughout the final week of the study. This created a five-day testing difference during week one, with some subjects being tested on the first day and some on the last day of the week. The same was true during the final week of the study. In an attempt to control for this discrepancy, subjects tested near the beginning (or end) of the first week were retested near the beginning (or end) of week 12. The effect of testing some subjects after being on the diet for five days could have affected the results across all the groups; however, the between-group results should not have been affected. 3. Because the cost of the weight-loss program included exercise instruction and prescription, it was inappropriate to ask some of the subjects not to exercise at all during the entire 12 weeks. Furthermore, the weight-loss program itself placed a strong emphasis on the importance of exercise, and most of the subjects would not have agreed to be in a non-exercise control group. Therefore, subjects exercising at 40% of HRR were used as a control group. 4. The duration of the current study was 12 weeks. Any changes in lean tissue that may have occurred after the 12-week experimental period were not measured. 5. A thorough search of the literature yielded no other investigations using methods similar to those of the current study. Therefore, it was not possible to compare the results of this study with those of many other investigations. 6. Variations in walking grade could not be accounted for when determining the exercise prescription. However, if the criteria of 40% and 60% of the HRR actually were maintained, changes in grade would not have affected the results of the study. 7. Changes in activities of daily living were not accounted for as the subjects lost weight and gained fitness. The subjects were not told to hold their daily activity patterns constant. 8. It was impossible to enforce the subjects' specified exercise intensities, but subjective feedback suggested that the subjects learned to hold 40% or 60% of the HRR quite well. CHAPTER II REVIEW OF RELATED LITERATURE Obesity is thought to have existed as far back as 15,000 years. However, changes in nutritional resources due to the agricultural revolution and a greater availability of cereal carbohydrates may have greatly increased the incidence of obesity in recent times (16). Reports prior to the 1950's on the prevalence of obesity are limited. First, much of the data related to height, weight and age have been collected as incidental parts of various studies and have not been presented in terms of accepted obesity criteria. Second, when obesity rates were recorded for a specific population, the data usually were based only upon existing height-weight reference tables. Third, obesity has not been a reported disease and rarely has been stated as the cause of death on death certificates. As a result, there are no valid prevalence figures for nations, and information generally has been based on local surveys conducting using both random and nonrandom groups of subjects (16, 19). In fact, in 1965 the 0.8. Department of Health, Education, and Welfare concluded that no data were available to support estimates of the incidence of obesity either in the total population or in any meaningful population group. In the late 1950's and early 1960's, total starvation was the method of choice for weight reduction in morbidly obese subjects (100). This method had the obvious advantage of rapid weight-loss. However, 11 these fasts caused large protein and potassium losses resulting in some cases of death. The addition of even small amounts of protein during a fast was found to dramatically reduce protein and potassium losses. This finding prompted the development of the so-called "protein-modified fast" which, in turn, resulted in the marketing of several liquid-protein diets (106). By the end of 1977, over 100,000 people had used these formulae, with a total of 60 deaths resulting from cardiac abnormalities (106). The National Center for Disease Control reported that these 60 individuals died suddenly and unexpectedly as a result of strict adherence to a very low-calorie, protein diet. The protein used was a solution of hyrolyzed gelatin or collagen, which was largely deficient in methionine, tryptophan and most other essential amino acids (106). Although 300 to 400 calories per day were contained in these liquid-protein diets, there was no vitamin, mineral or electrolyte supplementation (106). Ventricular tachydysrhythmias, prolonged QT intervals and low voltage complexes shown on the EKG occurred in conjunction with sudden deaths in 17 subjects who were using a liquid-protein diet. It has been suggested that the use of an incomplete protein of low biological value was the cause of these deaths (65). The sale of such products has hindered the acceptance of very-low-calorie diets (4). Recent low-calorie diets have been supplemented with 100% of the recommended daily allowance (RDA) for electrolytes, vitamins and minerals. Included in these supplements has been potassium, the lack of which has been associated with cardiac arrhythmias (106). Also included has been protein of high biological value, ranging from 50 to 100 grams per day and aimed at reducing nitrogen losses during fasting (106). Carbohydrates also are included, however, the ideal combination is not known at this time (106). The carbohydrate level in very low- calorie supplements usually is between 30 and 45 grams per day. The position statement of the American Dietetic Association on very-low-calorie diets is as follows: "Current very-low-calorie diets are safe when administered appropriately, and numerous studies under clinical and outpatient conditions have shown no serious adverse effects” (96, 106, 128, 131). mmmm There is a relatively high incidence of various diseases, metabolic disorders and other health-related complications in obese subjects (39). For example, as early as 1953, Keys et a1 (72) used skinfold measurements to calculate adiposity and concluded that there is an increased risk of developing coronary heart disease as body fatness increases. Coronary heart disease was then and is now the leading cause of death in the United States. As late as in 1984, Foss (39) suggested that controversy still persists as to whether or not obesity is a risk factor for cardiovascular disease and premature heart attacks. However, epidemiological studies have shown that obese persons are prone to hypertension and thus are at increased risk of incurring cardiovascular disease at a young age (26). Another cardiovascular risk factor known to be associated with obesity is hyperlipidemia. Buskirk (25) concluded that serum triglyceride levels are elevated and high-density lipoproteins are depressed in the obese subject. Reports of respiratory abnormalities such as obesity- hyperventilation syndrome, or Pickwickian Syndrome, have been described by Buskirk (24). The shallow irregular breathing and reduced lung volumes in the obese with Pickwickian Syndrome cause small airway closure and partial atelectasis leading to increased venous mixture. This probably reduces the pulmonary capillary circulation and inhibits alveoli perfusion. Foss (39) found a positive correlation between obesity and diabetes. He noted that diabetes mellitus presents three challenges for exercise therapists who are working with obese subjects. These challenges include ulcerations, hypoglycemia and ketoacidosis. Other specific conditions that are known to be associated with obesity are listed in Appendix B. As might be expected, there is also evidence that increased mortality is associated with obesity (17). Overall mortality rates have been shown to increase as fat weight increases (120). Although obesity clearly is an undesirable condition, the methods of remediation that frequently are used, fasting and very-low-calorie diets, have been associated with increased ketone production, decreased electrolytes, reduced maximal aerobic power and lowered high-density lipoproteins‘ when there is no concurrent program of exercise. Exeggise Retghtigh 9f Lean-£29! flééi The American College of Sports Medicine recommends that, as one stimulus for the loss of body weight and fat, exercise should be conducted a minimum of three days per week with a calorie expenditure of about 300 Real per session (54). However, to lose weight most effectively, one should both eat less and exercise more (20); and many studies have been published supporting the practice of combining diet and exercise (28, 54, 55, 59 70, 100, 123, 135). With regular exercise, lean-body mass appears to be retained even when caloric intake is restricted severely (27). This lean-body mass retention causes the resting metabolic rate to remain elevated more than it does during caloric restriction without exercise. In recent studies, resting metabolic rate has been associated with lean-body mass, but these studies have not involved changes in body composition brought about by regular exercise (53, 56, 62). In a review article by Oscai (85), the rates of weight change produced by exercise alone, exercise with food restricted to 400 Kcal per day and exercise with total fasting were studied. It was concluded that exercise combined with food restriction was the sensible approach for obese individuals who frequently could not tolerate neither severe caloric restrictions nor prolonged physical exercise. Also, when the added effects of exercise were compared to the effects of caloric restriction alone, exercise was found to provide protection against the . loss of fat-free weight (98). One explanation may be that during prolonged exercise, fatty acid mobilization increases as a result of elevated sympathetic activity. Therefore, the cumulative effects of daily exercise could account for both a fat loss and a retention of lean-body mass. Moreover, since fatty acid mobilization occurs for a time after exercise, further preservation of lean-body mass may result from the prolonged availability of energy from fat catabolism (100). In an early study (1963), Buskirk, et a1 (31) reported that exercise added to food restriction produces a relatively large negative caloric balance and accelerates the rate of weight-loss over that which can be obtained from either exercise or food restriction alone. Their subjects lost both body weight and fat at a faster rate when they were placed on a combined regimen of diet and exercise than they did when subjected to either treatment alone. Warwick et al (129) studied three obese women for 12 weeks on a 800-Kcal/day diet. Exercise for two hours per day, seven days per week, on a cycle ergometer was added and subtracted during alternating periods of three to four weeks. It was concluded that the addition of exercise to a reducing diet has no effect on either weight-loss or nitrogen balance during three to four-week intervals. However, Warwick (129) pointed out that the extent to which exercise increases total energy expenditure depends upon the type, duration and intensity of exercise as well as its effects upon resting metabolism and spontaneous activity. The conflicting results that have been reported (63, 98, 101) concerning weight loss and body composition may have been influenced by the diet and the intensity, duration and frequency of exercise used. In a three—week study done by Krotkiewski, et a1. (74), obese women on a SOD-Real diet were compared to similar subjects in a diet-plus- exercise group. The latter subjects expended 1650 Real three times per week in exercise. No differences between the two groups were found with respect to either body weight-loss or the preservation of lean- body mass. However, the differences may have been statistically nonsignificant simply because of the short period of time the study was conducted (74). Per Bjorntrop, et a1. (13) completed a six-month study on weight- loss in severely obese patients. The subjects participated in physical training without any dietary restrictions. The duration of exercise was 35 minutes plus five minute warm-up and cool-down periods. The exercise sessions were conducted three times per week. During the 35 minutes of exercise, there were five-minute intervals of strenuous exercise which yielded constant heart rates that were only 10 to 15 beats per minute below each subject's maximal heart rate. The intensity of exercise was not described before, between or after the strenuous training periods. Body weight and body fat showed no significant changes after six months (13). In a review of literature, Hagan (54) concluded that well- controlled, multiple-group programs involving exercise with caloric restriction constitute the best methods for achieving body weight and fat reduction. In one of Hagan's own studies, including exercise and diet, the overall regimen increased maximal oxygen consumption, decreased cholesterol and triglycerides and helped to preserve lean muscle mass (54). He recommended a diet of 1200 Kcal/day and physical exercise at least three days per week, for 20 to 30 minutes, at an intensity of 60% of maximum heart rate as a safe guideline. Pacy, et al. (101) concluded in their review article that exercise appears not to promote changes in body composition in favor of lean- body mass retention because the amount of exercise required to show benefits probably is well beyond the capability of obese individuals. They further observed that exercise alone is largely ineffective as a weight-loss technique but that it should be added to weight-loss programs based upon caloric restrictions. Body composition was evaluated by Hagan, et a1. (55) during 12- week programs of exercise and caloric restriction. The combined program consisted of a diet of 1200 Real per day and exercise five day per week for 30 minutes. The results did not support exercise-related retention of lean-body mass. Exercise intensity was not considered in this study, and the exercise prescription consisted only of the distance to be walked in 30 minutes. Remarkably large caloric expenditures of 500-900 Kcal per session were estimated for the subjects. Several studies have been published supporting decreased nitrogen _ losses and increased fat losses with combined diet and exercise (70, 102, 114, 130, 135). However, most controlled studies have failed to report a sparing of lean-body mass during the initial four to six weeks after the start of a diet (37, 126, 136). On the other hand, Pavlou, et a1. (70) did observe that the addition of exercise to a calorie- deficient dietary regimen preserves lean body mass, increases maximal oxygen consumption, increases strength and promotes a more effective reduction in fat stores than does diet alone. Studies measuring the preservation of lean-body mass and the loss of body fat in normal-weight subjects have yielded conflicting results. These studies have differed from one another in the amount of caloric restriction as well as in the intensity and duration of exercise used (63, 104, 124). As previously shown in obese individuals, data regarding body composition changes with exercise and caloric restriction also are conflicting. Most of these studies failed to determine the energy cost of the exercise, therefore making it impossible to explain the data on the basis of differences in either energy expenditure or food intake (101). Hagan (54) concluded that the best results occur when a weight-loss program: (a) provides at least 1200 Real per day from a dietary supplement; (b) allows a negative caloric deficit of between 500 and 100 Real per day; (c) includes behavioral modification techniques; and (d) incorporates a program of physical activity at least three days per week, for 20 to 30 minutes, at 60% of the subject's maximum heart rate. Exegcise ghg hetabolic Rggg The concept of resting metabolism dates from 1843 when Scharling discovered that a girl 19 years of age expired less carbon dioxide in absolute terms, and much less in relative terms, than did a boy 16 years of age (50). In 1981, Garrow (101) established that resting metabolic rate is the major determinate of total energy expenditure. Halliday, et a1. (56) concluded that in normal subjects resting metabolic oxygen consumption, measured in m1/02/min, is closely correlated to fat-free mass. Miller, et a1. (94) studied resting oxygen consumption in the obese and found the correlation between lean- body mass and the rate of resting oxygen consumption to be 0.92. Therefore, a reduction of muscle mass by either caloric restriction or inactivity may have the effect of reducing metabolic rate and total energy expenditure. Consequently, in any particular weight-loss program it is reasonable to seek a treatment which results in fat loss and spares lean tissue, thus preserving a normal metabolic rate. Pavlou, et a1. (70) has shown that physical exercise preserves lean-body mass during weight loss. Preservation of lean-body mass might help to maintain resting metabolic rate during caloric restriction in obese individuals (9, 19). In fact, in an article by Brehm (19) it was concluded that exercise reduces the diet-induced 20 loss of fat-free mass, and that metabolic rate is positively related to fat-free mass. Total resting oxygen consumption has been shown to be elevated in the obese state as the result of the higher absolute amounts of lean mass present in obese individuals (7, 68, 101, 109). However, as weight—loss decreases over time while the subject is on a hypocaloric diet, a decrease in resting metabolic rate occurs which may be attributed primarily to a decrease in lean tissue (7, 18, 36, 68, 97, 101, 104, 132). In one investigation involving two comparison groups, Davies, et a1. (36) observed that resting oxygen consumption declined significantly during an eight-week period during which caloric intake was restricted to either 330 or 780 Real per day. Values dropped 17% in both groups. Other investigations have shown as much as a 21% to 30% reduction in resting oxygen consumption (7, 132). Barrows, et a1. (7) found a reduction in the average resting metabolic rate of subjects given a 420 Kcal per day supplement for a period of four months. Investigators are in agreement that the resting metabolic rate stays elevated for a period of time after exercise. However, differences in the intensity, duration and total amount of exercise account for much of the variation in the magnitude of the excess post- exercise oxygen consumption (19). Most of the investigators that have found a long-term elevation in post-exercise metabolic rate have employed exercise of moderately high intensity. In a review article by Brehm (19), it was reported that: (a) Passmore, et al. found a 14% to 2] 18% elevation in resting oxygen consumption for seven hours after walking 16 km at 6.4 km/h and Maghlum et a1. (19) also found a significant elevation in the resting oxygen consumption 24 hours after subjects pedalled a cycle ergometer at 70% of their maximum oxygen consumption for 60 to 90 minutes. \ Other studies failing to find a long-term elevation in post exercise metabolism have used lower intensities of exercise (19). In the review article by Brehm (19), subjects who walked or jogged at less than 70% of their maximum oxygen uptake, or cycled at only 35% to 55% of their maximum oxygen uptake, failed to demonstrate a long-term rise in resting oxygen consumption. The research seems to indicate that an intensity threshold of at least 70% of maximum oxygen uptake (or possibly an intensity which exceeds ventilatory threshold) is required for an increase in post-exercise metabolism to occur in normal-weight subjects. These moderate amounts of exercise appear to have been similar to those used in the weight-loss treatments of sedentary or obese subjects, with some obese subjects being unable to maintain exercise intensities at even 70% of their maximum oxygen uptake. Since the obese may be unable to maintain even modest exercise intensities, it would be of interest to discover whether or not some sort of duration-intensity threshold exists (19). In comparison with the effects of diet alone, the use of exercise in combination with caloric restriction has resulted in accelerated fat loss, preservation of fat-free weight and prevention or deceleration of 22 a decline in resting oxygen consumption (104). Resting oxygen consumption appears to be the single best predictor of the rate of weight-loss of subjects on a fixed diet (9, 46). However, a recent study done by Phinney, et al (103) yielded conflicting results. In that study, very-low-calorie diets in combination with large quantities of aerobic exercise did not accelerate weight-loss and may have promoted a decline in resting metabolic oxygen consumption. Findings such as these underscore the need for a re-examination of the optimal combination of diet and exercise needed to best achieve fat-loss in obese patients (20). Body Composition using Bioelectgical Impgdahcg Extensive work has been done supporting the internal and external validity of bioelectrical impedance methods of determining lean-body mass in obese subjects (21, 50, 51, 61, 69, 76, 77, 84, 85, 86, 87, 113, 117). Bioelectrical impedance is based on the principle that impedance to the flow of an injected electrical current is related to the volume of a conductor (the human body) and the square of the length of the conductor (height) (50, 117). In an early study, Hoffer, et a1. (61) showed that total-body water (volume) and lean-body mass are strongly correlated with heightz/resistance. This finding resulted in the development of a simple, inexpensive, bedside method for estimating total-body water. The reproducibility of measuring total-body water and lean-body 23 mass has been established by Lukaski, et a1. (46). Test-retest correlation coefficients of 0.99 were reported for measurements of total-body water and lean-body mass (86). Kushner, et a1. (76) concluded that bioelectrical impedance is a useful clinical method for measuring changes in body composition. Johnson, et a1. (69) showed that bioelectrical impedance accurately indexes a change in body fat percentage as weight decreases. Gray, et a1. (51) studied the accuracy of bioelectrical impedance during a two-week fast and concluded that bioelectrical impedance measurements accurately reflect changes in total-body water. In another study, circumferences, skinfold thicknesses, bioelectrical impedance and hydrodensitometry were compared to determine their relative abilities to detect changes in body fat as weight decreases (69). Obese subjects were placed on a SOD-to 1500-Kca1/day diet for 21 days. The results indicated that each of the methods accurately assessed changes in the percentage body fat as weight decreased (69). Brodie (21) also studied bioelectrical impedance while subjects were on very low-calorie diets. Bioelectrical impedance was shown to be a reliable method for determining body composition even in subjects who are sensitive to dehydration while on a diet. Kushner, et a1. (26) validated the use of bioelectrical impedance analysis for body composition during weight reduction in obese subjects by direct comparison with total-body water as measured by stable-isotope dilution. A correlation of 0.97 was obtained. Previous studies have shown excellent correlations between 24 bioelectrical impedance, isotope dilution, and hydrodensitometry as methods of assessing fat-free mass in both lean and obese adults (76, 117). Denistometry is a highly reliable method of determining body composition and is the current ”gold standard" by which other methods are compared (76, 84, 85). In subjects ranging from 4% to 41% body fat, bioelectrical impedance measurements have been compared to densitometrically determined estimates of fat-free mass; and, in general, the values have been shown to correlate highly (0.95 to 0.98) with each other (85). In a cross—validation study by Segal, et al. (117), lean-body mass estimations by bioelectrical impedance and densitometry were compared at four geographical sites in large samples of men and women who varied widely in age and body fat content. The correlations ranged from .90 to .95, which again supports the validity of bioelectrical impedance in measuring lean-body mass (117). Summary One accepted procedure for weight-loss programs has involved the use of fasting, combined with a very low-calorie supplement, for a period of eight to twelve weeks. During this time some subjects have received behavior modification and exercise treatments. Numerous studies have looked at weight-loss and metabolic rate in obese subjects; however, conflicting results have been found. Variations in diets and exercise programs may have been the cause of 25 these discrepancies. Diet and exercise duration usually were not controlled as closely as they might have been. Literature searches revealed no studies that controlled for the volume of training (i.e. the energy cost of exercise) while accompanying a controlled 12-week modified fasting regimen. CHAPTER III METHODS AND MATERIALS A medical screening was performed on each subject by the OPTIFAST Physician prior to the start of the study; The screening consisted of a physical examination which included a SMAC-12 blood work up, a baseline resting EKG and a Millou Clinical Multiaxial Personality Inventory Test, which consisted of 175 true/false questions. This test was reviewed by a staff psychologist and was used as a tool to better understand each individual's personality. A nutritional assessment, given by a staff registered dietitian, which involved a three-day food diary describing the amount and type of food eaten including the time and place it was consumed. Program exclusion criteria are listed in Appendix C. Eligibility for the current study was defined as a body fat percentage greater than 25% for men and 30% for women. The duration of the study was 12 weeks. During that time, the subjects were on a supplemented fast consisting of 420 Kcals per day derived from 70 grams of protein, 30 grams of carbohydrate and 2.0 grams of fat with essential vitamins and minerals added (Appendix E). After explaining the subjects' rights and the risks involved in maximal exercise testing, written consent was obtained in accord with the Butterworth Hospital Institutional Review Board, Human Subjects Committee (Appendix D). 27 Subjects Necessary and sufficient sample size calculations determined that 14 subjects per group were sufficient to detect as statistically significant any difference between groups as large as or larger than 0.5 of a common standard deviation with Alpha and Beta levels were set at .01 and .05 respectively. In the current study, 35 subjects were recruited for each group. Attrition finally resulted in 20 subjects per group. The subjects enrolled in the program seeking weight-loss of their own free will or on the advice of their physicians. Once accepted into the study, the subjects were randomly assigned to an exercise group. Adherence t the Exercise Program Each subject was required to keep an exercise log which was inspected weekly. Any subjects not submitting weekly exercise logs immediately were contacted to determine if adherence to the exercise prescription was being maintained. Minimum program adherence for inclusion in the study was set at 85%. (The subjects were required to exercise at least 31 times out of 36 sessions to maintain 85% adherence). Subjects not achieving this level of adherence were dropped from the study. The subjects were contacted individually if problems arose concerning adherence to the program. These individual consultations were held as the subjects returned to the program facility to obtain 28 their supplements and to pay their weekly enrollment fees. During the 12-week supplemented fast, instructions regarding exercise adherence were presented in four one-hour lectures. Contracting with a significant other to sign the subject's exercise log each week, social support via other members of the group and monitoring of the subject's exercise program were used to encourage exercise adherence (59). Following the first maximal exercise test, the subjects were required to demonstrate that they could monitor their own pulse rates. Exercise heart rates were monitored by the subjects approximately every 10 minutes during each exercise bout to verify that the desired exercise intensity was being achieved. Thaining Procedures The current study involved two exercise intensities. The subjects in the high-intensity group (HI) exercised at 60% of their individual heart rate reserve (HRR). HRR was obtained by subtracting the subject's resting heart rate from his or her peak measured heart rate attained at the time of the first maximal exercise test (T1). The HRR then was multiplied by .60 and the resting heart rate was added (Appendix F). The subjects in the low-intensity control group (LI) exercised at 40% of HRR which was calculated in a similar manner. The subjects were stratified according to gender and then randomly assigned to the two groups. Each subject was instructed to walk as his or her assigned HI or L1 target heart rate, for a distance requiring an 29 energy expenditure of 300 Real, three time per week for a total Kcal expenditure of 900 Heals/week. This caloric deficity is in accord with the minimum guidelines for body composition changes set forth by the American College of Sports Medicine (4)., Specific exercise prescription methods for the current study are located in Part II of Appendix F. W The determination of the percentage of lean-body mass was made by Bioelectrical Impedance Plethysmography (BIP) using a localized 50-KH2 current-injection method (RJL Systems, Mt. Clemens, Michigan Model Za- 180-57). As compared to earlier models, the plethysmograph used has been improved by the addition of reactance and phase angle measurement equations. These variables, added to resistance, account for hydration abnormalities which are not usually present in healthy adults. Reactance and phase angle measurements (the arc tangent of reactance/resistance) are required to detect the hydration abnormalities that occur with rapid changes in body composition. Oxygen consumption was measured using a Medical Graphics 2001 system, (model CAD 2001 C-N). Measurement Procedures Prior to the start of the first maximal exercise test (T1), body resistivity (composition) was measured using the four-terminal portable impedance plethysmograph. Measurements were made in the supine 30 position with the limbs abducted 35 to 45 degrees from the body. Current-injection electrodes were placed at the phalangeal-metacarpal joint on the middle of the dorsal side of the left hand and 1/4 inch below the transverse (metatarsal) arch on the superior side of the left foot. Detector electrodes were placed on the midline of the posterior side of the left wrist at the level of the pisiform bone and ventrically across the medial maleous bone of the left ankle with the foot semiflexed. Resistance (R) to the flow of the 50 KHz injected current was measured on a 0-1000 ohm scale, and reactance (Xc) was measured on 3 0-200 ohm scale. Formulae provided by the manufacturer of the instrument were used to calculate the percentage of lean-body mass (84, 85, 97). Following the analysis of body composition, T1 was administered using the "Bruce" treadmill protocol (42) (Appendix G). Blood pressures and 12-lead EKG's were recorded every three minutes with heart rates being monitored continuously throughout the test. The end point for T1 was either volitional fatigue or one of the symptom- limiting conditions specified by the American College of Sports Medicine (4). Oxygen consumption was measured continuously by a pneumotachometer using breath-by-breath technology during T1. T1 was conducted in a hospital cardiology department with physician coverage available. The exercise laboratory was equipped with a crash cart and a defibrillator. 3] The exercise target heart rate for each subject was computed from the T1 results. The exercise prescription then was discussed with the subject and the exercise log was explained. The exercise program began during the first week of the 12-week supplemented fast. The second maximal exercise test (T2) was completed during the last week of the supplemented fast, week 12, using the same procedures as outlined for T1. The second analysis of body composition was made prior to T2. Analysis pf Data Before-to-after differences, independent of groups, were analyzed by dependent t-tests. Gain score differences between groups were analyzed by one-way analysis of variance. Gender differences between the exercise groups was tested by Chi-square analysis. Significance was set at the .05 level. CHAPTER IV RESULTS AND DISCUSSION The results of this study are presented in the followig order: demographic information, body compositon, exercise results and adherence results. An overall discussion of the findings is presented at the end of this chapter. Demographics Table 1 shows that the demographic characteristics of age and height were similar in the two training groups; however due to attrition only 5% of the L1 group were males, whereas 14% of the HI group were males. In an article by VanDale (124), Krotkiewski stated that exercise may have a greater effect on weight loss in males than in females. This difference could be due to gender-related variances in adipose tissue distribution. Krotkiewski showed that physical training produces greater changes in body composition with the male type of adipose tissue distribution (i.e. predominance in the abdominal region) than it does with the female type of distribution (i e. predominance in the femoral region). In the current study, a Chi-square analysis revealed that the differences in gender frequencies between the two exercise groups were not statistically significant (p<.05). Furthermore, in a recent study by Lampman (79), severely obese males and females were compared at rest and at peak treadmill exercise. Heart rates, systolic and diastolic 32 33 om.o ma.o MDA<>IQ m . a means ma ma moHeth on em muoonnsm mo.o e.m H e.mo m.m H m.me A.cav sesame mm.~ m.s H m.me m.s H m.mm Amuse mom dmammuw m manna mm m.mmdmw mm wannmmmw monmcmuozmo mm H mqmca 34 blood pressures and absolute and relative maximal oxygen consumptions were all similar. It would appear, therefore, that the slight variation in the final gender composition of the two comparison groups probably should not have affected the results of this study. Body Composition Results Table 2 shows that there were significant (p<.05) drops in total body weight, (15.3 kg) and total body fat, (14.09 kg) independent of the training intensity groups during the 12-week study. However, even more important is the fact that the absolute value of lean-body mass remained unchanged. Table 2 also shows that in terms of relative changes, there was a 9.1% reduction in body fat, resulting in a 9.0% increase in lean—body mass (p<.05). These results provide clear evidence that favorable alterations in body composition resulted from the combined diet and exercise program. There were no significant differences in body composition between groups (see Tables 3 through 5). However, note that the nonsignificant gain-score differences in Table 5 favored the HI group. Exercise Results The training results, independent of the HI and LI training groups, are given in Table 6. 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Although not investigated in the current study, the high recidivism and "yo-yo" effects seen with weight-reduction programs may be diminished when lean tissue is maintained or increased. A decrease in resting metabolism is well documented to be a common concomitant of weight-reduction programs (47, 109, 125, 132). figgy Composition In the current study, overall body weight (independent of groups) significantly decreased by 15.3 kg (p<.05) (Table 2). Similar previous studies have reported weight losses averaging up to 20 kg. However, these studies differed in exercise intensity and duration as well as in the amount of calories consumed (127). A between-group comparison showed that the changes in the two training-intensity groups were similar (Table 5). Weight decreased by 15.0 kg in the LI group and by 15.7 kg in the HI group. The major focus of the current study was lean tissue changes during the 12-week supplemented fast. Lean tissue, or lean-body mass, has high metabolic activity. Every pound of lean-body mass expends approximately 50 calories per day (5). The hypothesis, which was tested in the current study, was that lean tissue would be 46 significantly greater in the high-intensity (HI) group than in the low-intensity (LI) group (p<.05) by the end of the 12-week study. However, the results failed to support this hypothesis in that the percentage of lean tissue after training was similar in the two groups (Table 5). Lean-body mass did not change from before to after training in either group (Tables 3 and 4). Other studies investigating lean tissue have yielded inconclusive results. Pavlou (102) concluded that the combination of exercise and diet preserves lean tissue more effectively than does diet alone. However, Pacy (101) found that exercise does not appear to assist in lean tissue preservation. Most studies support increased fat losses with diet and exercise (70, 102, 114, 130, 135), but many fail to report a sparing of lean tissue during four-to-six week experimental periods (37, 126, 136). All of these studies differed in caloric restriction as well as in the intensity, duration and frequency of exercise. From the results of the current study, it can be concluded that there was no significant loss in lean tissue even though a significant reduction in total body weight was obtained. Furthermore, exercising at 60 percent of the subject's heart rate reserve offered no advantage either to body weight loss or to lean tissue preservation over that observed at 40 percent of the subject's heart rate reserve. It is noteworthy that the current study controlled daily caloric intake, daily caloric expenditure and 47 exercise intensity. In a 12-week training study by VanDale, et al. (124), subjects who exercised at 50 to 60% of their aerobic power four times per week significantly (p<.05) decreased their body fat by an average of 10.9 kg. Caloric intake was 611 calories the first four weeks, followed by 811 calories the last eight weeks. In the current study, body fat decreased (p<.05) by 14.9 kg when the subjects exercised at 40% or 60% of the heart rate reserve (Table 2). Lean tissue increased by 9.0% (p<.05); this was accompanied by a 9.1% decrease in body fat (p<.05). Overall, the 40 subjects increased their ratio of lean tissue to fat tissue by 45% during the 12-week caloric-restricted diet. That is, they started with a lean/fat ratio of 1.22 and increased their lean/fat ratio to 1.77 by week 12. Previous studies have revealed a decrease in the ratio of lean tissue to fat tissue at the conclusion of dieting programs (127). Table 5 compares the gain scores in body composition for the HI and LI groups. No significant differences (p<.05) were found in total weight, lean tissue, fat tissue or body surface area. The reason that there were no differences between groups is unknown. Perhaps the training duration and frequency an/or the program length were not sufficient to differentiate body composition changes between groups. It should be noted, however, that the training intensities in the current study were equivalent to 80% of the 48 measured peak heart rate for the HI group and 71% of the measured peak heart rate for the L1 group. The exercise intensity for the HI group was quite demanding, even for the individuals who train regularly. On the other hand, lowering the exercise intensity for the LI group from 40 to 30 percent of the heart rate reserve would have resulted in a target heart rate within ten beats of the resting heart rate for many of the subjects. Casual ambulating would have put these subjects at their target heart rate. The exercise intensities used in the study were representative of typical high- intensity and low-intensity work levels for obese subjects since most weight-loss programs recommend exercise at intensities similar to that of the LI group. Exercise frequency was three times per week, which seemed to be well tolerated. The subjects were required to walk a distance of 2.0 to 3.0 miles to expend 300 Real each session. This typically took 50 to 60 minutes at the designated heart rate. Many subjects complained that the walking distance required to expend 300 Kcal was quite rigorous. It would appear that if differential training effects between groups in lean-body mass were possible, either the study duration of 12 weeks or the frequency of exercising would have had to have been increased to produce such effects. 49 Miss L_n_grai in Exercise training resulted in significant (p<.05) increases in maximal oxygen consumption (ml/kg/min), as well as significant (p<.05) decreases in resting heart rate and resting systolic blood pressure, independent of the exercise intensity (Table 6). These changes are indicative of a training effect. The relative maximal oxygen consumption increased 5.0 ml/kg/min (p<.05) while the absolute maximal oxygen consumption measured in ml/min remained unchanged (P-.08). Therefore, the relative gain of 5.0 ml/kg/min in oxygen consumption appears largely to have been due to the observed 15.3 kg decrease in body weight. In a study done by Pavlou, et al. (102), 72 mildly obese male subjects were exercised three days per week for 8 weeks in an aerobic program at 70-85% of maximum heart rate. A significant increase in maximal oxygen consumption in absolute as well as relative terms was found. In the current study, the 9 bpm decrease in resting heart rate probably was, at least in part, the result of increased vagal tone, resulting in an enhanced stroke volume. Pre-test anxiety also may have enhanced the initial heart rate. A resting systolic blood pressure drop of 5.4 mmHg also was observed. A decrease in total peripheral resistance accompanying weight loss may have been responsible. However, Krotkiewski, et al. (73) determined that a significant decrease in blood pressure during a six-month exercise program involving obese women on an ad libitum 50 diet did not correlate with a reduction in body fat. A decrease in sympathetic nervous system activity, resulting from a decrease in test anxiety, may have contributed to the lower resting systolic blood pressure measured before the second maximal exercise test. Treadmill time significantly increased in the current investigation by 2.8 minutes (Table 6). This resulted in a one stage increase during the Bruce protocol. An extensive search of the literature revealed few relevant studies that included exercise training variables other than those associated with oxygen consumption. The effects of physical activity in 27 middle-aged obese women on self-determined (ad libitum) caloric restriction was studied by Lewis, et al. (82). The duration of the study was 12 weeks. The physical activity program involved 55 minutes of light gymnastics, intermittent jogging and brisk walking three days per week. The subjects exercised for 19 minutes at 80% of their previously determined maximal heart rates. In agreement with the current results, there were significant (p<.05) decreases in heart rate, systolic blood pressure and diastolic blood pressure at both three and six-month intervals. However, pre-test anxiety was not accounted for in the study. A comparison of the gain scores in the several exercise training variables revealed no significant differences between the HI and LI groups (Table 9). Increasing study duration and/or frequency of exercising may result in different findings. CHAPTER 2 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS The purpose of this study was to compare the effects of two intensities of exercise on the lean-body mass of obese subjects during 12 weeks of severe caloric restriction. The subjects had initial body fats greater than 25 percent for males and greater than 30 percent for females. All subjects were enrolled in an OPTIFAST weight-reduction program. The two exercise intensities were 40% and 60% of heart rate reserve. Frequency of training was three days per week, with 300 calories expended per exercise session. The mode of exercise was walking. The results showed that no significant loss of lean-body mass occurred during the 12-week period of caloric restriction. However, decreases in body weight, body fat and body surface area were observed (p<.05). When gain scores were analyzed by groups, no differences were observed between the effects of the two exercise intensities on various body composition variables. Overall, exercise training resulted in significant (p<.05) increases in maximal oxygen consumption (ml/kg/min) and treadmill time (min). These changes were accompanied by significant (p<.05) decreases in resting systolic blood pressure (mmHg) and resting heart rate (bpm). However, pre-test anxiety could not be eliminated as a possible contributing factor. A comparison of gain scores by groups revealed no significant differences in training 5| 52 effects between the two exercise intensities. The data from this study can be generalized only to obese individuals enrolled in weight reduction programs that do not require total fasting. The exercise intensity guidelines used in this study for the L1 group are typical of those used with many supplemental fasting programs. Conclusions The following two conclusions may be drawn from the results of this investigation: 1. As compared to exercise at 40% of the heart rate reserve, exercise at 60% of the heart rate reserve offers no physiological advantage with respect to body composition enhancement or cardiorespiratory fitness. 2. During a period of severe caloric restriction, exercise at 40% of the heart rate reserve maintains lean-body mass despite a loss of up to 15 kg. in total body weight. Recommendations l. During a weight-loss program involving severe caloric restriction, obese individuals should exercise at intensities of approximately 40% of their heart rate reserves in order to spare lean-body mass. 2. Graded exercise tolerance tests should be used to determine peak heart rates and to prescribe appropriate training intensities for 53 obese subjects who are planning to participate in weight—loss programs. Further research is needed to determine the optimal exercise intensity for lean-body mass preservation in obese subjects during period of severe caloric restriction. A study is needed, which incorporates a sedentary control group, in order to define more fully the effects of exercise on lean body mass in obese subjects enrolled in an supplemented fasting program. Studies allowing variations in program duration, training duration, mode of exercise (i.e. strength training), and frequency of exercise should be undertaken to determine how these factors might affect body composition in obese subjects during weight-loss programs. 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