obese people large fat 311 (R).
(photo credit: Reuters)
CHICAGO – In a study conducted among 25 healthy individuals
living in a controlled setting who were randomized to overconsumption of
different levels of protein diets, those consuming the low-protein diet
had less weight gain compared to those consuming normal and high
protein diets, and calories alone, and not protein appeared to
contribute to an increase in body fat, according to a study in a recent issue of JAMA. The researchers also found that protein did contribute to changes in energy expenditure and lean body mass.
has become a major public health concern with more than 60 percent of
adults in the United States categorized as overweight and more than 30
percent as obese," according to background information in the article.
The role of diet composition in response to overeating and energy
dissipation is unclear.
George A. Bray, M.D., of the Pennington Biomedical Research Center,
Baton Rouge, La., and colleagues conducted a study to determine whether
the level of dietary protein differentially affected body composition,
weight gain, or energy expenditure under tightly controlled conditions.
The randomized controlled trial included 25 US healthy, weight-stable
male and female volunteers, ages 18 to 35 years, with a body mass index
between 19 and 30. The first participant was admitted to the inpatient
metabolic unit in June 2005 and the last in October 2007. After
consuming a weight-stabilizing diet for 13 to 25 days, participants were
randomized to receive diets containing 5 percent of energy from protein
(low protein), 15 percent (normal protein), or 25 percent (high
protein), which they were overfed during the last 8 weeks of their 10-
to 12-week stay in the inpatient metabolic unit. Compared with energy
intake during the weight stabilization period, the protein diets
provided approximately 40 percent more energy intake, which corresponds
to 954 calories a day.
All participants in the study gained weight and there were no
differences by sex. The rate of weight gain in the low protein diet
group was significantly less than in the other two groups (6.97 lbs. [3.16
kg] vs. 13.3 lbs [6.05 kg] for the normal protein diet group and 14.4
lbs [6.51 kg] in the high protein diet group).
"Body fat increased similarly in all three protein diet groups and
represented 50 percent to more than 90 percent of the excess stored
calories. Resting energy expenditure, total energy expenditure, and body
protein did not increase during overfeeding with the low protein diet,"
the authors write.
Lean body mass (body protein) decreased during the overeating period by
1.5 lbs. (0.70 kg) in the low protein diet group compared with a gain of
6.3 lbs. (2.87 kg) in the normal protein diet group and 7 lbs. (3.18
kg) in the high protein diet group. Resting energy expenditure (normal
protein diet: 160 calories/day; high protein diet: 227 calories/day)
increased significantly with the normal and high protein diets.
"In summary, weight gain when eating a low protein diet (5 percent of
energy from protein) was blunted compared with weight gain when eating a
normal protein diet (15 percent of energy from protein) with the same
number of extra calories. Calories alone, however, contributed to the
increase in body fat. In contrast, protein contributed to the changes in
energy expenditure and lean body mass, but not to the increase in body
fat," the researchers write.
"The key finding of this study is that calories are more important than
protein while consuming excess amounts of energy with respect to
increases in body fat."
In an accompanying editorial, Zhaoping Li, M.D., Ph.D., and David Heber,
M.D., Ph.D., of the University of California, Los Angeles, write that
the results of this study "informs primary care physicians and policy
makers about the benefits of protein in weight management."
"The results suggest that overeating low protein diets may increase fat
deposition leading to loss of lean body mass despite lesser increases in
body weight. Policy makers and primary care physicians need to
understand the role of the Western diet in promoting overweight and
obesity. Because this diet increases the risks of overnutrition through
fat deposition beyond that detected by body mass index, the method used
to assess the current obesity epidemic and the magnitude of the obesity
epidemic may have been underestimated. Clinicians should consider
assessing a patient's overall fatness rather than simply measuring body
weight or body mass index and concentrate on the potential complications
of excess fat accumulation. The goals for obesity treatment should
involve fat reduction rather than simply weight loss, along with a
better understanding of nutrition science."