Diet Study: Protein May Help Tame Appetite
But Trim Fat to Keep Calories in Check, Say Researchers
July 13, 2005 -- If your appetite is wrecking your diet, protein might help,
new research shows.
Protein may help patrol the space between you, the fridge/menu/vending
machine, and belt-busting eating habits.
You needn't banish carbohydrates from your plate, researchers write in the
American Journal of Clinical Nutrition.
Of course, there's a catch. Forget about slathering protein in fat-laden
sauces. Mind your calories, too, and expect more studies to probe the
Still interested? If so, here are the appetite experiment's details.
Step No. 1: Full Disclosure
Nineteen healthy adults from Seattle took part. They were about 41 years
old, on average.
Average BMI (body mass index) was 26. That's overweight but not obese.
First, they wrote down every morsel they ate for three days. Then, they
checked in with a dietitian to make sure they didn't skimp or gorge on
Next, they got a heads-up from the researchers, who included University of
Washington endocrinologist David Weigle, MD.
Weight loss isn't the study's point, Weigle's team told subjects. Those
hoping for weight loss were dismissed.
Step No. 2: Head to the Kitchen
Participants got carry-out meals -- and a few ground rules -- from the
Rule No. 1: Only eat the food provided. Rule No. 2: Eat all of it.
For the first two weeks, half of all calories came from carbs, 15% from
protein, and 35% from fat.
Then, protein was doubled and fat was halved. Carbs held steady throughout
Step No. 3: Eat as Much as You Like
Four weeks into the study, the rules changed.
The higher-protein foods remained. But subjects no longer had to eat all of
The instructions were simple: Eat when you're hungry. Stop when you're full.
Subjects were also told not to try to change food intake, physical activity, or
Step No. 4: Weighing the Results
Weight didn't change during the study's first two phases. But participants
reported feeling fuller on the higher-protein diet.
When they didn't have to eat all the higher-protein food, they ate about 441
calories less per day. As a result, they lost nearly 11 pounds, about 8 pounds
of which was fat.
Protein vs. Carbs
The effect could partly explain why people lose weight on low-carb diets associated with high
proteins, suggest the researchers.
"Our results suggest that less emphasis should be placed on carbohydrate
restriction without regard for ... increases in dietary fat," write Weigle
"Replacing a portion of dietary fat with protein may result in weight
loss comparable with that reported with low-carbohydrate diets while minimizing
the adverse long-term effects of increased dietary fat," they continue.
However, more studies are needed on dietary protein's effects on kidney
function and calcium before high-protein diets can be widely
recommended for weight loss, they write.