Contact: Phyllis Picklesimer
University of Illinois at Urbana-Champaign
Is one diet as good as another? U of I study says no and tells you why
Any diet will do? Not if you want to
lose fat instead of muscle. Not if you want to lower your triglyceride
levels so you'll be less likely to develop diabetes and heart disease.
Not if you want to avoid cravings that tempt you to cheat on your diet.
And not if you want to keep the weight off long-term.
latest study shows you have a better chance of achieving all these
goals if you follow a diet that is moderately high in protein," said
Donald Layman, a University of Illinois professor emeritus of
nutrition. The research was published in the March
Journal of Nutrition.
new study followed the weight-loss efforts of 130 persons at two sites,
the U of I and Penn State University, during 4 months of active weight
loss and 8 months of maintenance.
Two previous studies had looked at short-term weight loss; this one was designed to look at long-term effects, he said.
both plans were equal in calories, half the group followed a
moderate-protein diet (40% carbohydrates, 30% protein, 30% fat) while
the other followed a diet based on USDA's food-guide pyramid (55%
carbohydrates, 15% protein, 15% fat).
"Persons in the first group ate twice the amount of protein as the second group," said Layman.
And the difference in protein made all the difference in improved body composition and body lipids, he said.
the amount of weight lost in both groups was similar, at 4 months
participants in the protein group had lost 22 percent more body fat
than members of the food-pyramid group. At 12 months, the
moderate-protein dieters had lost 38 percent more body fat.
additional protein helped dieters preserve muscle. That's important for
long-term weight loss because muscle burns calories—if you lose muscle,
and you used to be able to consume 2,000 calories without gaining
weight, you'll find that now you can only eat, say, 1,800 calories
without weight gain," he said.
What were the effects on
lipids? Although at 4 months the food-guide pyramid appeared to be more
effective in lowering LDL and total cholesterol levels, at 12 months
LDL levels came back up until both diets were equally effective, Layman
"This is the first study to show that short-term changes
in LDL cholesterol are not maintained with long-term weight loss. Most
scientists believe that high cholesterol is more a factor of genetics
than of diet," he said.
But the moderate-protein diet had by
far the bigger effect on lowering triglycerides, and that lasted as
long as individuals remained on the diet, he said.
"Of the two
types of lipid problems, high triglycerides pose a greater risk for
heart disease. Approximately twice as many people have high
triglycerides, and people with this condition are approximately four
times more likely to die from heart disease," the scientist said.
ensure compliance, participants met every week for weigh-ins and
nutrition instruction. "We taught participants how to follow their
diet, how to grocery shop, and how to prepare the meals. They also
measured everything they ate three days a week," he said.
that report there is no difference among diets also report that
subjects were not carefully following the diets," said Layman. "It's
very important to realize the difference between diet compliance and
The protein diet was easier to follow and
maintain long-term, with 64 percent of the moderate-protein dieters
completing the study compared to 45 percent of dieters using the
high-carbohydrate diet, Layman said.
"Subjects on the
moderate-protein diet reported that they weren't as interested in
snacks or desserts, and they didn't have food cravings. When you eat
protein, you feel full longer," he said.
Average weight loss
for the protein group was 23 percent higher than the food-pyramid
group, with 31 percent of "completers" in the protein group losing more
of than 10 percent of their initial body weight versus 21 percent of
the food-pyramid group.
of the study are Ellen Evans of the U of I Department of Kinesiology
and Public Health; Donna Erickson, Jennifer Seyler, and Judy Weber of
the U of I Department of Food Science and Human Nutrition; and Deborah
Bagshaw, Amy Griel, Tricia Psota, and Penny Kris-Etherton of The
Pennsylvania State University Department of Nutritional Sciences.
It was funded by the National Cattlemen's Beef Association, The Beef Checkoff, and Kraft Foods.