With more than two-thirds of U.S. adults classified
as either overweight or obese, developing guidelines
to help achieve and maintain a healthy body weight,
is a key national health objective.
New research is helping to explain the causes and possible
solutions for the near-epidemic weight gain in Americans
over the last few decades. Notably, a study by Dansinger,
et al, published last year in the Journal of the American
Medical Association, showed that the amount of weight
dieters lost after one year was modest, regardless of
the diet selected (Atkins, Ornish, Weight Watchers or
Zone). Importantly, the JAMA study showed a 42% drop
out rate by study participants. A message from these
studies is that the current crop of popular "fad"
diets is not a practical long-term solution to the obesity
Part of the solution to this growing health issue may
lie in findings that were published in two other recent
studies. In the first study, highlighted last July in
the American Journal of Clinical Nutrition, researchers
were interested to learn why low-carbohydrate diets
help subjects to lose weight. What
they found is that the macronutrient mixture, namely
high-protein, not the low-carbohydrate content of popular
diets like Atkins, helps people to lose weight.
The reason appears to be that protein is more satiating
and energy-burning than either carbohydrate or fat.
In the study, researchers varied the amount of protein
and fat study participants consumed while keeping carbohydrate
constant. During the initial two weeks, 19 healthy individuals
were placed on a weight-maintaining 2,000-calorie diet
that consisted of 15% (by energy) protein, 35% fat and
50% carbohydrate. For the next two weeks, also in a
2,000-calorie diet, protein was doubled to 30% while
fat was reduced to 20% and carbohydrate remained the
same at 50%. In the final 12 weeks of the study, participants
did not have a caloric limit but had to maintain the
high-protein diet. To monitor results, patients were
asked how hungry they felt between and after meals.
In addition, researchers measured levels of important
satiety and hunger-related hormones including leptin
and ghrelin. The study excluded individuals with a body
mass index of 30 or higher; those who did aerobic exercise
for more than 30 minutes three times a week; those who
used tobacco, alcohol, or had diabetes or any other
What the researchers found is that people became more
satiated on the high-protein (30%) diet. During the
second two weeks of the trial, patients reported feeling
more satiated on the high-protein diet despite no significant
change in leptin levels. Even during the 12 week phase
when participants did not have any caloric restrictions,
on average they consumed 450 fewer calories per day
and lost about 11 pounds overall. The study results
could not be explained by the hunger hormone ghrelin
which increased or the satiety hormone leptin which
decreased during this phase of the research.
a healthy source of protein, we recommend Vitamedica
A second study, by Howard, et al was published in the
January 2006 issue of JAMA. The researchers wanted to
test the hypothesis that a low-fat, high-carbohydrate
diet - a diet which is promoted by organizations such
as the American Cancer Society and American Heart Association
- has contributed to the rise in obesity over the past
several decades. Not surprisingly, this is a notion
that has been purported by advocates of low-carb diets
like Atkins and The South Beach Diet.
The low-fat study was part of the Women's Health Initiative
which followed about 48,000 postmenopausal women for
an average of 7.5 years. About 40% of the women in the
study were assigned to a low-fat diet with the remaining
60% of the women assigned to a control group. At baseline,
both sets of women consumed at least 32% of their daily
caloric intake from fat. Women in the low-fat group
were told to consume no more than 20% of their daily
caloric intake from fat. These women also participated
in a series of group sessions designed to reduce dietary
fat intake while increasing complex carbohydrate intake.
The control group was not given any specific dietary
restrictions but received a copy of the Dietary Guidelines
for Americans. Neither group was instructed to exercise
or to restrict their caloric intake.
During the first year of the study, women on the low-fat
diet lost an average of 4.8 pounds compared to the control
group. In addition, many of the women maintained their
weight loss over the next several years. Based on these
results, the researchers concluded that a low-fat diet
may prevent the tendency for women to gain weight during
their postmenopausal years. They also concluded that
a low-fat diet paired with complex carbohydrates such
as fruits, vegetables and whole grains has not been
a contributing factor to the rising rate of obesity
in this country.
For the majority of healthcare professionals who are
involved in providing care to an increasingly obese
patient population, these two studies provide direction
for weight management in these patients. Based on these
findings, encouraging patients to consume 30% of their
calories from protein, 20% from fat and 50% from complex
carbohydrates seems prudent. Guidance should be based
on helping patients to make quality choices within each
macronutrient group, with emphasis on lean sources of
protein, unsaturated fats and complex carbohydrates
from fruits and vegetables.
a healthy source of protein, we recommend Vitamedica
National Center for Health Statistics, 1999-2002 National
Health and Nutrition Examination Survey (NHANES)
Dansinger et al, "Comparison of the Atkins, Ornish,
Weight Watchers, and Zone diets for weight loss and
heart disease risk reduction," JAMA 2005; 293:43-53.
Howard et al, "Low-fat dietary pattern and weight
change over 7 years," JAMA 2006; 295:39-49.
Weigle et al, "A high-protein diet induces sustained
reductions in appetite, ad libitum caloric intake, and
body weight despite compensatory changes in diurnal
plasma leptin and ghrelin concentrations," Am J
Clin Nutr 2005; 82:41-8.
Reprinted with permission from Vitamedica.
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