Exercise training and severe caloric restriction: Effect on lean body mass in the obese

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Exercise Training And Severe Caloric Restriction: Effect on Lean Body Mass in the Obese Brian C. Leutholtz, PhD, Randall E. Keyser, PhD, William W. Heusner, PhD, Vernon E. Wendt, MD, Lionel Rosen, MD ABSTRACT. Leutholtz BC, Keyser RE, Wendt VE, Heusner WW, Rosen L. Exercise training and severe caloric restriction: effect on lean body mass in the obese. Arch Phys Med Rehabil 1995;76:65-70. • 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 _+ 7.7 years; 106 +_ 26kg; body fat > 25% men, > 30% women) on a commercially prepared OPTIFAST 420kcal/day supplemented fast were randomized into groups that exercised at target heart rates corresponding to 40% and 60% of the heart rate reserve (HRR) at the start of the program. Training volume was similar for both groups at approximately 300kcal per session three times per week for 12 weeks. Body weight, body fat, and lean weight were similar for both exercise intensity groups at week one. Overall, body weight decreased by 15.3 _ 6.7 kg (p -< .05), and body fat decreased by 14.9 +_ 5.0 kg (p -< .05) for the 40 subjects, whereas lean weight remained unchanged. No significant differences in body weight, body fat, or lean weight were observed between the two groups. The results of the current study indicated 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 900kcal/week. Lean weight remained unchanged and accompanied a 14.9 _+ 5.0-kg decrease in body fat, which may have resulted when the volume of exercise (ie, 900kcals/wk) was factored into the exercise prescriptions. 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 when the total volume of exercise training is controlled.

© 1995 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Excessive body fat is a contributing factor to health problems and increase one's risk of developing atherosclerosis. The incidence of hypertension, hyperlipidemia, and diabetes is increased in obese individuals who also suffer from the obesity-hyperventilation syndrome and many other medical complications. 1'2 All-cause mortality has also been reported to be higher in the obese. 3'4 Despite the apparent health problems associated with excessive body fat, universal standards by which obesity can be defined or measured are not available. A quotient of body weight (kg) and the squared height (m2), known as the body mass index, greater than 25 to 30 has been used to define obesity. 5'6 The quotient does not account for lean body weight. Garrow 7 recommended that obesity be defined as a body fat of greater than 22% for men and 28% for women. Other investigators have used measures of 25% or more for men and 30% or more for women to define obesity. 8'9 Although a consensus definition of obesity has not been reached, these latter criteria represent From the Department of Health, Physical Education and Recreation, Old Dominion University, Norfolk, VA (Dr. Leutholtz); Department of Clinical Cardiology, Butterworth Hospital, Grand Rapids, MI (Dr. Wendt); School of Medicine, Department of Physical Therapy, University of Maryland, Baltimore (Dr. Keyser); and Department of Physical Education and Exercise Science (Dr. Heusner), Department of Psychiatry (Dr. Rosen), Michigan State University, Lansing, MI (Drs. Heusner, Rosen). Submitted for publication April 29, 1994. Accepted in revised form July 22, 1994. This manuscript was completed to fulfill the requirements for a PhD in clinical exercise physiology. All data was collected at Butterworth Hospital in Grand Rapids, MI. No commercial party having a direct or indirect interest in the subject matter of this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Brian C. Leutholtz, PhD, Old Dominion University, HPER Dept, Room 140, HPE Building, Norfolk, VA 23529-0196. © 1995 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/95/7601-305753.00/0

apparently high levels of body fat at any age and classify 15% of the adult population as obese. 8 Successful weight loss requires a caloric imbalance such that energy expenditure exceeds caloric intake. Caloric deficit can be achieved by increased physical activity and decreased caloric consumption. The most effective method for weight reduction appears to be a combination of increased physical activity and caloric restriction. 1°15 Total resting energy expenditure and lean body mass (LBM) are generally greater in the obese. The resting metabolic rate (RMR) decreases by as much as 21% after a hypocaloric diet, primarily as a result of concomitant LBM reductions. 16't7 LBM retention has been implicated as an essential factor for maintaining a target body weight after cessation of dietary restriction in women. 18-2°A reduction in LBM and RMR may help explain the regaining of weight observed in 77% to 100% of individuals who participated in various lowcalorie weight reduction programs. 21-23When caloric restriction is combined with an exercise regimen, accelerated weight loss, enhanced leanness, and maintenance of RMR may result. 12'14'24-27There are conflicting reports 24"a8'29on the effectiveness of exercise in preserving a desirable body composition and metabolism during weight loss. These conflicts may be the result of variations in the exercise regimen, whereby the volume of exercise was not controlled and caloric expenditure was increased as the subject decreased body weight and became more fit. Exercise intensity also may be an important determinant of body composition alterations and of weight loss because the relative contributions of fat and glucose to the total metabolic substrate fluctuate with increases and decreases in exercise intensity. The purpose of this study was to compare the effects of high- and low-intensity exercise regimens on LBM in obese Arch Phys Med Rehabil Vol 76, January 1995

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SEVERE CALORIC RESTRICTION AND EXERCISE, Leutholtz

Table 1: Physical Characteristics of Subjects by Group Group Characteristics

HI

LI

p Value

A g e (yrs) H e i g h t (in) Subjects (N) Women Men Target H R

43.5 ___ 7 . 8 65.4 _4- 3.6 20 15 5 138 _+ 19

39.8 _+ 7.3 65.3 __+ 3.3 20 18 2 125 _+ 13

0.13 0.90 -----

Significance at p < .05.

individuals during a 12-week period of severe caloric restriction.

SUBJECTS AND METHODS Forty obese subjects (33 women and 7 men, 41 ± 7.7 years) with a mean weight of 106 ± 26kg who were participating in a 12-week supplemented fasting weight loss program (OPTIFAST a) volunteered for this study. Inclusion criteria were a body fat determination by bioelectrical impedance of greater than or equal to 25% for men and 30% for women. A physical examination, SMAC (Sequential Multiple Analytical Computerized)-12 blood chemistry profile, resting electrocardiogram (ECG) and the Million 175question Personality Inventory were completed for each subject. Program and study exclusion criteria were those recommended by the American College of Sports Medicine (ACSM) for exercise testing and prescription s and the following OPTIFAST exclusion criteria for the OPTIFAST program: coronary or peripheral atherosclerosis; ketosis prone diabetes mellitus; chronic use of steroids; bleeding peptic ulcer; history of suicide attempts; active thrombophlebiffs; alcohol abuse; pregnancy or lactation; any other conditions that would limit exercise or caloric restriction. None of the subjects ingested beta blockers or other exercise limiting agents during the study. The experimental procedure was explained, and written informed consent was obtained from each subject in accordance with the institutional review board. Subjects were randomly assigned to either a highintensity (HI) or low-intensity (LI) exercise group (n = 20 per group). Group descriptive information is given in table 1. APPARATUS Because of the immense size and body mass of the subjects in this study, hydrostatic weighing was difficult. Therefore, body composition analyses were made by bioelectrical impedance plethsysmography (BIA) using a localized 50-KH2 current injection method,b The BIA software included reactance and phase angulation measurements (the arc tangent of reactance/resistance) to account for hydration abnormalities that may occur with rapid changes in body composition and that are not usually present in healthy adults. Subjects were checked daily for any signs of rapid fluid shifts by the OPTIFAST physician and staff and continually encouraged to drink plenty of fluids. BIA has also been reported to be extremely reliable, which is the important variable to ascertain with the test/retest methods used in this study, s Maximal exercise tests were performed using a metabolic cart interfaced with a motor-driven treadmill and 12-lead electrocardiograph. ~ Expired Arch Phys Med Rehabil Vol 76, January 1995

gas analysis was performed using a metabolic cartd consisting of rapid response, zirconium oxygen, and infrared carbon dioxide analyzers. Ventilatory volume was computed from flow measurements made by an onboard pneumotachometer. Data was collected and stored breath by breath, and averages of eight consecutive breaths were used as data points when determining VO2. Information related to the exercise training regimen was recorded after each of the exercise sessions in a personal exercise log.

PROCEDURE Each study subject's body composition was assessed by having the subject lie supine with limbs abducted 35 to 45 °. Current injection electrodes were placed at the metacarpalphalangeal joint in the middle of the dorsal side of the right hand and one-quarter inch below the transverse (metatarsal) arch on the superior side of the right foot. Detector electrodes were placed on the midline of the posterior side of the right wrist at the level of the pisiform bone and vertically across the medial maleous of the right ankle with the foot semiflexed. Resistance to the flow of the 50-KH2 injected current was measured by BIA on a 0- to 1000-ohm scale and reactance was measured on a 0- to 200-ohm scale. Subjects then underwent maximal exercise testing. The Bruce protocol was used. Resting heart rate (HR) and blood pressure (BP) were recorded after a 10-minute supine rest. Exercise HR (from ECG) and BP (by auscultation) were recorded after each 3-minute work stage and at peak exercise. Oxygen uptake (VO2) was assessed with a Medical Graphics 2001 metabolic cart. The exercise test ended when subjects indicated that they could not continue. In all cases, fatigue was cited as the reason for test termination, with respiratory quotient values greater than 1.15 in all cases signifying that anaerobiosis and a maximal test effort were achieved. The subjects then began an extended period of fasting, supplemented by a 420-kcal per day OPTIFAST nutritional preparation distributed in five equal servings per day, totaling 70g of protein, 30g of carbohydrate, and 2g of fat (table 2). Subjects were randomly assigned to HI and LI intensity exercise groups (n = 20 subjects per group). HI exercised at a target HR of 60% of the heart rate reserve (HRR) computed as .6 (peak HR - resting HR) + resting HR, and LI exercised at a target HR of 40% of the HRR, computed as .4 (peak HR - resting HR) + resting HR. Subjects were instructed on how to take their pulse and practiced until they could accurately determine it; they were checked on their accuracy at least twice a week when they reported for their educational sessions and supplement refills. Target HRs were recorded in a daily exercise log. Each subject walked a distance that required the expenditure of 300kcal, three times a week, in both HI and LI. Thus, total training volume, ie, distance walked, was held constant at 900kcal per week for both groups and was estimated by extrapolating the measured oxygen consumption that corresponded to the subject's target HR obtained from their maximal functional capacity exercise test. Energy expenditure was then determined at the target heart rate. Subjects were then instructed to walk a prescribed distance at their target HR to expend the desired (300) amount of calories per session. After each exercise session, subjects completed a log, recording distance, time,

SEVERE CALORIC RESTRICTION AND EXERCISE, Leutholtz Table 2: Nutrient Breakdown of Optifast 70. 4.3 oz/Daily Serving Percentage U.S. RDA Protein Carbohydrate Fat Calories Vitamin A Vitamin D Vitamin E Vitamin C Folic acid Thiamine Riboflavin Niacin Vitamin B6 Vitamin B~2 Biotin Pantothenic acid Calcium Phosphorus Iodine Iron Magnesium Copper Zinc Potassium Sodium Manganese Selenium Chromium Molybdenum Vitamin K Choline Chloride

70g 30g 2.0g 418 5,000IU 400IU 30IU 90mg 0.4mg 2.25mg 2.6mg 20mg 3.0mg 6.0mcg 0.36mg 10rag 1.0g 1.0g 150mcg 18mg 400rag 2.0mg 15mg 1,955mg 920rag 4.0rag 150mcg 150mcg 300mcg 100mcg 100mg 2.2g

150 ** ** ** 100 100 100 150 100 150 150 100 150 100 120 100 100 100 100 1O0 100 100 100 ** ** ** ** ** ** ** ** **

Amino Acid Content Grams/100g of Protein Essential Amino Acids L-Isoleucine L-Leucine L-Lysine L-Methionine L-Phenylalanine L-Threonine L-Tryptophan L-Valine

5.45 9.28 7.52 3.02 5.44 4.24 1.26 6.52

Nonessential Amino Acids L-Alanine L-Arginine L-Aspartic acid L-Cystine L-Glutamic acid Glycine L-Histidine L-Proline L-Serine L-Tyrosine

3.91 4.21 7.17 0.81 20.58 2.43 2.67 11.00 6.37 5.23

Abbreviation: RDA, recommended daily allowance. **No RDAs are established for these vitamins.

HR, and perceptions of the exercise session. Logs were reviewed in person on a weekly basis to assess subject participation. Subjects were also contacted at least once each week to ensure that the exercise prescription was rigorously followed. The subjects were required to exercise at least 31 out of 36 sessions to maintain the 85% adherence rate that was set for the study. Exercise logs were required to be signed off after each session by a "significant other" ie, husband, wife, etc, to help ensure compliance. 48 All subjects completed the study and OPTIFAST program according to the exercise adherence requirements previously listed. The dietary and exercise programs continued for 12 weeks, after which maximal exercise tests and body composition analyses were again performed. Initial and postprogram exercise test procedures were identical, as were initial and postprogram body composition analyses techniques.

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S T A T I S T I C A L ANALYSIS This study tested the hypothesis that LBM would be higher in HI when compared with LI after a 12-week regimen of supplemented fasting. A necessary and sufficient sample size was determined to be 15 subjects per group, at 95% power (power = 1-/3), with 5.76kg as the smallest acceptable between group difference in LBM gain scores and expected variance of 14.8kg (alpha = .01). Main effect differences in total sample means for before and after participation were assessed for statistical significance by dependent t tests. Before-to-after gain score means were evaluated by one-way analysis of variance. Differences in baseline scores between groups were assessed by independent t tests. Between-group gender differences were evaluated by chi-square. An alpha level of .05 was required for statistical significance (p -.05) with respect to baseline and gender differences. An alpha level of less than .01 was required for significance with respect to differences in before-and-after means and before-to-after gain scores (p --< .01). Data are presented as mean _+ standard deviations. RESULTS Body composition for the total sample (n = 40) is described in table 3. A significant reduction in body weight was associated with decreased body fat after the weight loss regimen. LBM remained unaffected. The overall combined caloric restriction and exercise regimen resulted in a higher percent LBM and lower percent fat at completion of the program when compared before the start of the program. A demographic overview of HI and LI is provided in table 1. Statistically similar gender assignments, age, and height were noted. Before the program, body composition characteristics for HI and LI were similar. Significant differences in body weight, body fat, and LBM were not observed between groups at the conclusion of the study as a result of the HI and LI exercise intensities (table 4). EXERCISE TRAINING Significant between group differences in resting and peak VO2, HR, BP, and treadmill time were not observed before the training regimen. These variables were also similar for the two exercise intensities at the conclusion of the study (table 5). However, significant differences for the total sample, in relative VO2 (ml/kg/min), resting HR, resting blood pressure, and treadmill time were observed for all the subjects (table 6). 1 Peak absolute VO2 (ml/min) was not significantly changed by the program, p < .08), which could be explained by the large change in body weight that occurred in the subjects. Adherence to the exercise program was 98.1 + 3.7% (35.5 _+ 1.3 sessions out of 36) for LI and 98.0 _ 4.2% (35.3 + 1.5 sessions out of 36) for H I - - n o t significantly different. DISCUSSION This analysis failed to support the hypothesis of enhanced leanness with HI over LI. Overall, subjects lost 15.3kg of body weight and 9.1% body fat with no significant ~ .01) loss of LBM as a result of the caloric restriction and exercise regimen. A significant improvement in peak relative Arch Phys Med Rehabil Vol 76, January 1995

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SEVERE CALORIC RESTRICTION AND EXERCISE, Leutholtz Table 3: Body Composition Analysis of Total Sample Variable

Body weight (kg) LBM (kg) ' % LBM Fat mass (kg) % ]7at mass

Before Participation

After Participation

106 58.3 55.6 47.6 44.4

90.7 58.0 64.6 32.7 35.3

4- 25.6 ___ 13.5 _+ 5.6 _+ 15.2 4- 5.6

_+ 21.6 4- 12.3 ___ 7.3 _ 12.7 ___ 7.3

Before to After Participation

STD E r r o r

p Value

-15.3 -0.30 +9.0 -14.9 -9.1

1.08 0.48 0.50 0.81 0.49

0.01 0.34 0.01 0.01 0.01

Significance at p -< .01

VO2 was observed. However, peak absolute V O 2 w a s not significantly increased, suggesting that the observed increase in exercise tolerance may have been largely caused by body weight reduction and maintenance of LBM. Resting HR and resting systolic BP were significantly lower after training than before training, suggesting that a training effect may have occurred. Significant differences in peak VO2, resting HR, and before-to-after gain scores were not observed between HI and LI. Extensive work has been conducted regarding the internal and external validity of bioelectrical impedance methods for determining LBM in obese subjects. 5'3°-41 Kushner and colleagues 42 concluded that bioelectrical impedance is a useful clinical method for measuring changes in body composition. The ACSM 8 recognizes bioelectrical impedance as a reliable method for measuring body composition. In the current study, reliability was the main concern when subjects were retested at'the end of their supplemented fasting regimen. Johnson and~ associates 34 reported that bioelectrical impedance accurately indexes a change in body fat percentage as weight decreases when circumferences, skinfold thicknesses, bioelectrical Iimpedance, and hydrodensitometry were compared to determine their relative abilities to detect changes in body fat as weight decreases. Brodie 3° measured 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 very low-calorie diet. When considering that most of the individuals used in the study were too large to fit comfortably in our hydrostatic weighing tank and refused this procedure, bioelectrical impedance was considered the best method to assess the body composition changes in the obese subjects. With a proven, strong reliability accuracy using BIA, which was important when testing the subjects before and after the caloric restriction, BIA was considered the best method.

peak HR reserve during a 12-week 420-kcal/day weight loss program (table 4). This decrease in body weight was concomitant with an overall decrease of 15.3kg of body weight, and accompanied a change of the subject's LBM of -0.30kg or a relative 9% increase (table 3). There were no significant differences between groups before or after the study when body composition variables were compared at the two exercise intensities (table 4). In 1981, Pacy43established that RMR is the major determinate of total energy expenditure, and consequently, Miller and colleagues44 studied resting oxygen consumption in the obese and found a correlation between lean body mass and the rate of oxygen consumption to be 0.92. Because LBM or muscle tissue is metabolically active, additional gains of approximately one pound of muscle tissue will increase the RMR by approximately 50kcal per day.5 In any particular weight loss program it is reasonable to seek a treatment that resuks in fat loss and LBM retention to preserve metabolic rate. Maintenance of metabolic rate could be an important determinant in weight regain after weight reduction programs. By retaining LBM and maintaining an elevated metabolic rate during and after weight loss, it may be possible to curb the "yo-yo" effect associated with the increase in body fat and weight gain that occurs a short time after the conclusion of most diet programs. The current study reported a retention of LBM versus body fat with an actual increase in the lean/fat ratio of 1.22 (58.3kg/47.6kg) before and 1.77 (58.0kg/32.7kg) at the conclusion of the 12-week diet and exercise program. This provided clear evidence of favorable changes in body composition. However, it should be noted that the study was highly gender biased, where 33 of the 40 subjects were women. A follow-up study measuring weight regain is indicated to determine whether individuals retaining or increasing most Table 5: Exercise Test Results by Group After Participation

Body Composition

Group

A reduction of 15.0 to 15.7kg was reported in obese subjects when exercising at 40% and 60%, respectively, of their measured Table 4: Body Composition by Group After Participation Group Characteristics Body weight (kg) LBM (kg) % LBM Body fat (kg) % Body fat

HI -15.7 +0.2 +9.6 -15.9 -9.6

__+5.3 4- 2.1 4- 3.2 __. 4.9 _ 3.2

Significance at p --- .01

Arch Phys Med Rehabi! Vol 76, January 1995

LI -15.0 -1.2 +8.3 -13.3 -8.3

_+ 8.4 -2_ 3.8 ~ 2.9 4- 5.2 4- 2.9

p Value 0.76 0.30 0.17 0.20 0.17

Characteristics

HI

LI

p Value

Resting heart rate (bpm) Resting systolic pressure (mmHg) Resting diastolic pressure (mmHg) Peak heart rate (bpm) Peak systolic pressure (mmHg) Peak diastolic pressure (mmHg) Peak VO2 (ml/kg/min) Peak VO2 (ml/min) Test duration (min)

83 _+ 11 118 -4- 12

82 4- I1 120 4- 10

0.91 0.62

80 _+ 6

82 _+ 10

0.71

172 160 78 26 2,444 9.1

Abbreviation: bpm, beats per minute. Significance at p -----.01

___ 20 _ 19 __ 8.0 4- 5 _+ 829 4- 1.6

175 164 81 28 2,457 10.0

-4- 15 _+ 22 -- 10 __ 4 4- 770 4- 1.7

0.67 0.61 0.38 0.14 0.96 0.16

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SEVERE CALORIC RESTRICTION AND EXERCISE, Leutholtz Table 6: Exercise Test Results Analysis for the Total Sample Before Participation

Variable Resting heart rate (bpm) Resting systolic pressure (mmHg) Resting diastolic pressure (mmHg) Peak heart rate (bpm) Peak systolic pressure (mmHg) Peak diastolic pressure (mmHg) Peak VO2 (ml/kg/min) Peak VO2 (ml/min) Test duration (min)

91.2 125.2 83.9 172.6 164.1 82.5 22.0 2,339.9 6.8

_+ 14.8 -+ 13.7 -+ 7.5 _+ 19.2 _+ 22.4 + 8.9 - 3.4 -+ 605.6 -+ 1.9

After

Participation 82.8 119.8 81.3 173.9 161.8 80.0 27.0 2,451.0 9.6

-+ 11.1 _+ 12.2 _+ 8.5 -+ 17.5 -+ 20.9 +- 9.2 _+ 5.0 _+ 783.0 -+ 1.7

Gain Score -9.1 -5.4 -2.6 +1.3 -2.3 -2.5 +5.0 +111.1 +2.8

STD Error

p Value

3.00 2.21 1.40 0.74 4.15 1.87 0.60 61.5 0.25

0.01 0.02 0.08 0.46 0.58 0.18 0.01 0.08 0.01

Abbreviation: STD, standard error of estimate. Significance at p ~ .05

or all of their LBM during caloric restriction are able to maintain their ideal body weight when compared with subjects who decrease LBM during dieting and exercise programs.

Exercise Training The ACSM recommends that, to stimulate the loss of body weight and fat, one should exercise a minimum of 3 days a week, with a caloric expenditure of about 300kcal per session. s'12 Many studies have been published supporting the practice of combining diet and exercise to achieve weight loss goals, n'15'45-47 Conflicting results, however, have been reported when prescribing the optimal intensity and duration for body fat loss and LBM retention. Various diet and exercise durations may be the reason for the discrepancies, along with not controlling the volume or caloric expenditure during the studies' exercise prescription. Moreover, diet and exercise usually were not closely controlled. A search of the literature has showed no other studies that controlled for the volume of training, ie, the energy cost of exercise while accompanying a controlled 12-week 420-kcal/day modified fasting regimen. This could be a key reason why so many investigators have reported conflicting results in weight loss studies, and it could also be a factor accounting for the almost total retention of LBM we observed. Further studies investigating variations in program duration, training frequency, mode of exercise, and caloric deficit should be conducted to determine how these factors might affect body composition in obese subjects during weight loss programs. Adherence to the exercise program was tracked with weekly exercise logs required of all subjects. A study by Robison and associates 4s found exercise adherence was enhanced when a significant other was contracted to sign the subject's exercise log each week.

Exercise Intensity In accordance with the ACSM, the following exercise intensity and duration guidelines for obese subjects are practiced: " T h e exercise program intensity should be at or below the low end of the typical heart rate range, with the duration of each session compensating to achieve an expenditure of 200 to 300kcal. ''8 When interpreting these guidelines, the "low end of the typical heart rate range" needs further clarification for consistency when prescribing exercise in the obese.

In this study, the training target heart rates corresponding to 40% and 60% of the subjects HRR were equivalent to 80% of the measured peak HR for the high-intensity group and 71% of the measured peak HR for the low-intensity group. When subjects were compared by group at the study's conclusion, (tables 4, 5), no differences in the body composition or cardiovascular variables were reported. This suggests that exercise at 60% of the measured peak HRR offers no advantage when compared with exercise at 40% of the subjects's measured peak HRR in obese individuals, represented by a power, 1-/3 of 95% with a necessary and sufficient sample size of 15 subjects per group. However, further studies are needed to determine the specific optimal target HR intensity range and duration guidelines for LBM preservation in obese subjects during periods of severe caloric restriction. For ethical and monetary reasons, the subjects used in this study served as their own control group. Without insurance reimbursement for the subjects, it was considered unethical to prohibit some of the subjects from exercising thereby allowing other subjects a weight loss advantage. Subjects enrolled in the study were not willing to pay the OPTIFAST program fees and then not exercise.

Cardiovascular Variables No differences in the cardiovascular variables were reported as a result of the two exercise intensities (table 5), suggesting that the two exercise intensities demonstrated similar training results. However, a significant decrease below the p - .05 level for the entire sample did exist with resting HR, systolic blood pressure, and an increase in test duration when these were compared at the conclusion of the study. These changes were accompanied by an increase in relative maximal oxygen consumption, suggesting a total conditioning effect as a result of the exercise intensities used. However, decreases in HR, systolic blood pressure, and test duration could have been the result of weight loss. Furthermore, the increase in relative and not absolute VO2 may have been caused by the reduction in body weight and maintenance of LBM (table 6). A study using a nonexercise control group would be needed to solve this uncertainty. In summary, it appears that exercising at target HRs corresponding to 40% and 60% of the measured peak HRR are equally effective when decreasing body fat and preserving lean body mass in obese subjects during a 12-week 420kcal Arch Phys Med Rehabil Vol 76, January 1995

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SEVERE CALORIC RESTRICTION AND EXERCISE, Leutholtz

per day supplemented fasting program, when the total amount of work is held constant. Exercise at the above intensities combined with an exercise prescription that controlled for the volume of exercise (900kcal/week) during supplemental fasting resulted in almost total retention of LBM with a loss of 15kg of body weight. A beneficial study would be one that incorporates a sedentary control group to define more completely the exercise effects on LBM in obese subjects enrolled in a supplemented fasting program.

26. 27. 28. 29. 30.

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31. 32. 33. 34.

35.

36. 37. 38. 39. 40. 41. 42.

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