of exercise and diet has long been prescribed for severe obesity.
Support for this rational comes from reports of the effects of
strenuous exercise and physical training in the non-obese, sedentary,
athletic, and those with only mild or moderate degrees of obesity.
Relatively fewer studies have been conducted with severe or morbid
obese subjects (23).
Exercise alone is probably insufficient to bring about significant
fat loss except in individuals who are extremely motivated. The
combination of modest caloric restriction and physical training
may be necessary to induce favorable changes in body composition
(27). Although prolonged, intense physical exercise may promote
weight loss, more moderate exercise, as practiced by non-athletes
may not induce significant weight loss. In some cases, weight
gain has actually been reported (28, 29). The combination of
modest caloric restriction and physical training may be necessary
to induce favorable changes in body composition (27).
In a landmark study in 1976, Zuti
& Golding compared changes in body composition in three
treatment groups. In group one, each subject reduced dietary
intake by 500 Calories daily. Group two increased energy expenditure
by 500 Calories daily. Group three combined a dietary restriction
of 250 Calories and an energy expenditure of an additional 250
Calories. Through the 16 week study, all groups lost comparable
weight, 11.7 lbs., 10.6 lbs., and 12 lbs. respectively. The exercise
and combination groups lost more fat, 9.3 lbs., 12.6 lbs., and
13 lbs. respectively. Group one experienced a loss of muscle
mass while the group two gained the greatest muscle mass, -2.4
lbs., 2 lbs., and 1 lb. respectively (30).
Regular exercise tends to preserve lean body mass even with
caloric restriction (31). Van Loan, M. D. et al. evaluated the
effects of endurance exercise on fat-free mass and nitrogen balance,
with energy restriction or with energy intake to meet non-exercise
needs in obese women. Endurance exercise had a slower rate of
weight loss and a lower loss of fat free mass than the diet and
exercise group. Nitrogen balance was more positive in the endurance
exerciser group than the diet and exercise group. Although, changes
in fat free mass, assessed by nitrogen balance, were different
from the results obtained by total body electrical conductivity.
This difference suggests decreased FFM were due to fluid losses,
which were confirmed by deuterium dilution procedures. This study
demonstrates that body protein stores may be maintained during
periods of endurance exercise and dietary restriction in obese
The major fraction of daily energy expenditure in the obese
comes from their resting metabolism, although exercise can contribute
to a substantial portion (33). Lean body mass retention tends
to maintain resting metabolic rate. Among other factors, lean
body mass is related to resting metabolic rate (34). Shinkai,
S., et al. concluded aerobic exercise enhances the effect of
moderate dietary restriction by augmenting the metabolic activity
of lean tissue in mildly obese middle-aged women (35).
The combination of moderate energy restriction and either
resistance or aerobic exercise induces significant reductions
in visceral and subcutaneous adipose tissue and are thus effective
means of reducing total and upper-body obesity in obese women
(36). The American College of Sports Medicine's Guidelines for
Exercise Testing and Prescription asserts that both weight training
and aerobics can contribute to a loss of fat, yet they claim
aerobic exercise is more efficient because it involves a sustained,
high rate of energy expenditure (4). Weight training seems to
be superior in preserving or increasing fat-free mass during
a calorie restrictive diet (37) and increasing functional strength.
In 1988, Ballor, D. L. et al.
assessed the effects weight training on body composition in an
8 week weight loss study. Forty obese women were randomly assigned
to one of four groups: diet without exercise; diet plus weight
training; and weight training without diet. The authors concluded
that caloric restriction diet supplemented with a resistive weight
training program results in maintenance of lean body weight compared
with dieting alone. Furthermore, they found that weight training
resulted in comparable gains in muscle area and strength in both
weight training groups; with and without diet (38).
In 1989, Walberg, J. L. commented on the value of weight training
in the treatment of obesity. He noted that resistance exercise
appeared to prevent the loss of or even increase muscle mass
during energy restriction. Walberg argued that resistance exercise
is less likely than aerobic exercise to acutely increase lipid
and energy utilization but may indirectly aid weight reduction
by increasing lean tissue and metabolic rate. He concluded that
the value of aerobic exercise during weight loss was apparent,
but the potential of resistance exercise in weight remained unclear
Donnelly, J. E. et al. (1991), studied the benefits of aerobic
exercise and weight training combined with a very low calorie
diet. He discovered that changes in body weight, percent fat,
fat weight, and fat-free mass, were not different between exercise/diet
groups and diet groups. All groups exhibited declines in resting
metabolic rate. This study failed to show advantages of any exercise
regimen over diet alone for weight loss, body-composition changes,
or declines in resting metabolic rate, although limited improvements
in work capacity were reported in the exercise groups. Conversely,
strength improvements were found in the exercise groups that
included strength training (40).
It should be noted that exercise is less likely to induce
changes in resting oxygen uptake, adipose, and water weight when
combining severe dietary restriction than those employing moderate
dietary restrictions (41). Likewise, Dengel, D. R., et al. concluded
that in older, obese men, hypocaloric dieting combined with aerobic
exercise training does not attenuate the loss in fat-free mass
that occurs during weight loss by hypocaloric dieting alone (42).
Conversely, Sweeney, M. E. et al. found that moderate calorie
restriction (70%) may offer an advantage over severe energy restriction
(30%) because it produces a greater energy loss relative to energy
deficit. Although women in the severe energy restriction group
lost more weight (mean +/- SE: 15.1 +/- 1.4 verses 10.8 +/- 1.0
kg.), fat (11.7 +/- 1.1 verses 8.3 +/- 0.6 kg.), and fat-free
mass (2.8 +/- 0.3 verses 1.8 +/- 0.3 kg.) than the moderate calorie
restriction group (P < or = 0.05). The overall energy loss
relative to energy deficit was greater in the moderate calorie
restriction group (0.80 +/- 0.07) compared with the severe energy
restriction group (0.52 +/- 0.05; P < or = 0.01). Conversely,
exercise had no significant effect on energy loss relative to
energy deficit (43).
Physical training has been valued in the treatment of obesity
for elevating mood, reducing hunger, and improving the likelihood
of a successful outcome (44). Holm et. al. reported a temporary
suppression of the appetite after the initial bouts of a conditioning
Caloric intake does not seem to change in proportion to energy
expenditure during inactivity or exhaustive work. Yet, within
these extremes, caloric intake does seem to change in accordance
to the demands of energy expenditure (46). Staten found that
men increased their intake by 200 Calories per day when subjected
to 5 days of exercise (1 hour at 70% Vo2 max) whereas women did
Exercise can result in health and fitness benefits in the
obese independent of weight loss. An increase of fitness can
decrease the risk of cardiovascular disease and type 2 diabetes,
even if no weight loss is observed.
Strenuous exercise and physical training can improve insulin
sensitivity (12, 48). Interestingly, athletes and well-trained
people possess a more efficient insulin-mediated glucose uptake
than their sedentary counterparts (29). The addition of exercise
to a low-calorie diet may prevent glucose tolerance impairment
which seems to be associated with dieting alone (24). Regular
intense and prolonged exercise can significantly lower plasma
insulin concentrations with little effect on glucose tolerance.
This effect has been attributed to improved insulin sensitivity
and occurs with or without an accompanying body fat reduction
(49). Although, it appears the effects of physical training on
insulin sensitivity may be related to exercise's effects on adiposity
Tremblay, A. et al. conducted a study to evaluate the additive
effect of exercise and a low fat diet on body weight, body composition,
and metabolic profile in obese women. At the conclusion of the
study, the subjects were still overweight, but their plasma glucose
and insulin during an oral glucose tolerance test were similar
to values obtained in a sample non-obese women. Furthermore,
plasma lipid and lipoprotein levels were found to be normal with
the exception of plasma apo B and HDL-C levels. The researchers
concluded that aerobic exercise training and a low fat diet can
normalize the metabolic profile of obese women, even if their
adiposity remains higher than that of lean women (51).
Weight loss and fat reduction can decrease arterial pressure,
lower plasma triglyceride and cholesterol concentrations, and
can result in cardiovascular improvements (52). Likewise, regular
exercise can lower plasma triglyceride levels in obese individuals.
It is still unclear whether this change is due to the effects
of regular exercise on metabolism or because of weight loss (53).
In overweight women, regular exercise has been shown to slightly
reduce hypertension, even with no or only slight weight reduction
A multifaceted weight reduction program, including diet, exercise
and behavior modification, has been shown to be more effective
than other weight reduction programs (55). An increase of calorie
expenditure is the major goal in prescribing weight loss programs.
A balance between intensity and duration should be manipulated
to yield a high total caloric expenditure. Approximately, 300
to 500 Calories each bout and 1000 to 2000 Calories per week
for adults is recommended. Since many obese individuals are at
an increase risk for orthopedic injury, nonweight-bearing activities
may initially be recommended. Likewise, a variation of exercise
modes and modifications in frequency and duration may be required.
An intensity of 60% or less of functional capacity or maximal
heart rate may be maintained to improve cardiorespiratory endurance
(4). Although weight loss through exercise and modest calorie
restriction is slow, the likelihood of achieving successful weight
maintenance is greatly enhanced through physical activity.