Oct. 8, 2001 -- High-protein diets -- The Atkins Diet, The Zone, Sugar Busters, Stillman, and Protein Power -- are very popular. But they may be risky to long-term health, according to a new advisory from the American Heart Association's nutrition committee.
The basic premise of these diets is that people can eat all types of proteins but must restrict -- and sometimes eliminate -- other foods, especially carbohydrates like cereals, grains, fruits, vegetables, as well as milk products. The diets have been around for years but have faded in and out of popularity.
"The concern is that people on these diets eat more saturated fat and cholesterol but get very few of the essential vitamins, minerals, fiber, and other nutritional elements in carbohydrates," says Alice Lichtenstein, DSc, a professor of nutrition at Tufts University and vice chairwoman of the nutrition committee of the American Heart Association (AHA).
"There are no long-term studies of these high-protein diets," she tells WebMD. However, scientific evidence suggests that the diets carry "great potential" risk of heart disease as well as problems for the kidneys, bones, and liver, she says.
In its study, the AHA committee looked at each diet's philosophies, including foods to eat and avoid, diet composition, recommended supplements, health claims, and the practicality of each diet. They also assessed the diets' ability to help people lose weight and maintain that loss.
Researchers found that the high-protein diets run counter to guidelines set by every major health organization in the country, Lichtenstein tells WebMD. These groups include the American Dietetic Association, American Cancer Society, and the National Institutes of Health.
All the diets recommend excessive protein, which often leads to too much total fat and saturated fat, says the AHA study. The Zone and Sugar Busters omitted or severely restricted carbohydrates. All the diets were deemed as unsafe over the long term because they do not provide adequate nutrition or support healthful eating.
The following are some of the health risks of high-protein diets, according to the experts:
- They may increase LDL, or the level of "bad" cholesterol, since a diet rich in animal protein often contains saturated fat and cholesterol. That effect is compounded when high-carbohydrate, high-fiber plant foods -- which naturally help lower cholesterol -- are limited or eliminated.
- They may increase blood pressure, since fruits, vegetables, low-fat dairy products, and whole grains have been shown to lower blood pressure.
- They may promote bone-thinning osteoporosis, since excess protein in the diet triggers the body to excrete calcium during urination.
While the diets all caused initial weight loss, the Atkins and Stillman diets mostly caused water weight loss, the study says. The Zone, Protein Power, and Sugar Busters diets caused weight loss via calorie restriction, but rigidity of the diet and limited food choices made them impractical for the long term.
A popular premise of high-protein diets is that excess carbohydrates cause elevated insulin levels, which in turn, promotes storage of body fat, according to the study. Supporters of high protein diets say that the high amount of protein and fat relative to carbohydrates helps reduce insulin levels. The researchers counter, however, that protein stimulates insulin secretion, and changes in calorie intake do not influence insulin action.
Bottom line: high-protein diets aren't a good way to lose weight, says Chris Rosenbloom, PhD, chairwoman of nutrition at Georgia State University in Atlanta and spokeswoman for the American Dietetic Association.
"Almost everyone I've seen who has been on this diet can't keep the weight off," Rosenbloom tells WebMD. "Initially, they'll lose maybe 25 pounds. But then it comes back."
The initial water weight loss is "the diuretic effect, which happens when you restrict carbohydrates," she says. "On the bathroom scales, it looks like you've dropped weight, but it's not fat weight."
Without carbohydrates, the diets often create a condition called ketosis, which serves to curb appetite. "It's the body's natural response to starvation," she tells WebMD. "It keeps you from feeling hungry. It makes sense that the body would give us a mechanism to protect us during true starvation."
However, that effect doesn't last forever, she says.
The average person requires 102 grams of protein a day, and that should come from lean animal and vegetable proteins. In fact, eating too much protein -- in excess of your caloric needs -- will cause weight gain, says Lichtenstein.
To truly lose weight, the rule of thumb is to eat a nutritionally adequate diet, with a daily minimum of 1,200 calories for women and 1,500 calories for men, unless instructed by your doctor to limit your calories even further.
But energy output -- exercise -- that's what makes the biggest difference in weight loss, Lichtenstein tells WebMD. "There's no magic trick."