healthy eating reduce body fat and preserve muscle in adults better than diet
alone, according to a study funded and conducted by the National Institute of
Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National
Institutes of Health (NIH).
NIDDK senior investigator Kevin Hall, PhD, analyzed
the individual effects of daily strenuous exercise and a restricted diet by examining data from 11
participants from the reality television program "The Biggest Loser."
Researchers measured body fat, total energy expenditure, and resting metabolic
rate 3 times: at the start of the program, at week 6, and at week 30, which was
at least 17 weeks after participants returned home. Participation in the
program led to an average weight loss of 128 pounds, with about 82% of that
coming from body fat, and the rest from lean tissue.
Hall used a mathematical computer model of human
metabolism to calculate the diet and exercise changes underlying the observed
body weight loss. Because the TV program was not designed to directly address
how the exercise and diet interventions each contributed to the weight loss,
the computer model simulated the results of diet alone and exercise alone to estimate
their relative contributions.
At the competition's end, diet alone was calculated to
be responsible for more weight loss than exercise, with 65% of the weight loss
consisting of body fat and 35% consisting of lean mass such as muscle. In
contrast, the model calculated that exercise alone resulted in participants
losing only fat, and no muscle. The simulation of exercise alone also estimated
a small increase in lean mass despite overall weight loss.
The simulations also suggest that the participants
could sustain their weight loss and avoid weight regain by adopting more
moderate lifestyle changes, such as 20 minutes of daily vigorous exercise and a
20% calorie restriction, than those demonstrated on the television program.