Protein real star of low-carb diets
To reach a healthier weight -- with fewer hunger pangs -- consider eating more lean protein.
A new study points to protein’s power to satisfy hunger better than either fat or carbohydrates. The findings also could help explain the recent clamor for low-carbohydrate diets, which are high in protein.
This is “telling us that one of the reasons why the low-carbohydrate diets seemed to work is not because of low carbohydrates, but because of high protein,” said Arne Astrup, head of human nutrition at the Royal Veterinary and Agricultural University in Copenhagen.
“Look at Atkins, South Beach and the Zone,” said Astrup, author of an editorial accompanying the study in this month’s American Journal of Clinical Nutrition. These diets provide “30 to 40% of calories from protein,” he noted.
Thirty percent of daily calories as protein -- about twice what most people eat and the upper limit recommended by the Institute of Medicine -- is the amount that University of Washington researchers gave to 19 participants in the study. All were about 10 pounds overweight and had maintained their weight for at least three months. Prospective participants interested in dieting were eliminated from the study.
Food was prepared and supplied by the research team. Participants lived at home but met with researchers twice a week to be weighed and receive more food.
During the first two weeks of the trial, participants maintained their weight by eating 15% of calories as protein, 35% as fat and 50% from carbohydrates. They were instructed to eat all the food supplied or to return any remaining to allow the researchers to measure how many calories were eaten.
In weeks three and four of the trial, participants also maintained their weight but shifted to a diet containing twice the amount of protein and about half the fat. Remaining calories came from healthy carbohydrates, including plenty of fruit, vegetables and whole grains.
As before, participants were instructed to eat all the food or return it for measurement. “They complain about it because they feel very full on the high-protein diet,” said David Scott Weigle, professor of medicine at the University of Washington and the study’s lead author.
For the last 12 weeks of the study, participants received 15% more food each week and the freedom to eat as much of it as they wanted. To avoid nutritional boredom, participants could also eat one meal of their choosing weekly and drink as many as three alcoholic beverages a week.
Left to their own devices, participants spontaneously cut their intake by 441 calories daily. They lost an average of 11 pounds, while reporting feeling full and satisfied.
Hormones regulating appetite stayed at levels that normally boost hunger, Weigle said, suggesting that high-protein diets somehow affect the brain. If the brain perceives that lower levels of appetite-stimulating hormones are normal, he said, “then it would continue to turn down hunger.”
Even so, experts caution that eating 30% of daily calories as protein may not be safe for everyone, because it could overtax kidneys in those who already have kidney problems, or diabetes or glucose intolerance.
Here’s how researchers boosted protein in the study. (The recipes are available on www.leanplateclub.com.)
* Add nonfat dairy products. Drink skim milk with meals and use it instead of water to make oatmeal or “creamy” soups, such as tomato. Snack on nonfat yogurt. Use shredded nonfat or low-fat cheese for pizza, tacos and for grilled cheese sandwiches on whole wheat bread. Add nonfat dry milk to mashed potatoes and casseroles.
* Eat more lentils and beans. Not only are they high in protein, but they pack complex carbohydrates that don’t increase blood sugar and contain plenty of fiber. Tofu, soy milk and soy-based meat substitutes are also protein rich. Or add a little soy powder to orange juice to boost protein.
* Crack an egg. Egg whites are pure protein with no fat or cholesterol. Hard-boil and fill with guacamole, salsa or bean dip, or chop and sprinkle on salads. Egg substitutes contain no cholesterol and less fat than regular eggs. Or use one whole egg with extra egg whites to make fluffy, high protein omelets or frittatas.
* Eat more lean cuts of meat, poultry and fish. Skinless turkey and chicken breasts were frequent mainstays as was beef lasagna made with lean ground beef and ground turkey.
