|Johns Hopkins School of Medicine
Dangers of High-Protein, Low-Carbohydrate Diets for People With Diabetes
Johns Hopkins Diabetes White Paper, 2002.
The Johns Hopkins White Papers are in-depth special reports written for the consumer by some of the nation's leading doctors at the country's leading hospital and medical school.
Maintaining a healthy body weight is important for both the prevention and treatment of diabetes. Excess body weight increases the risk of developing diabetes; for overweight people with the disease, losing weight can improve blood glucose control and reduce the risk of long-term complications.
Losing weight is difficult, however, and many people resort to fad diets. Among the most popular ones today are high-protein, low-carbohydrate diets that promise rapid weight loss by following a food plan that is high in protein but limits foods rich in carbohydrates, such as fruits, vegetables, and grains. Some examples are Dr. Atkins' New Diet Revolution by Robert C. Atkins, M.D., Protein Power by Michael R. Eades, M.D. and Mary Dan Eades, M.D., Sugar Busters! by H. Leighton Steward, M.S. and coauthors, and The Zone by Barry Sears, Ph.D. According to the authors of these diets, high levels of insulin cause obesity by promoting the storage of calories as body fat. They claim that when a person reduces the amount of carbohydrate in the diet, the body produces less insulin and weight loss occurs.
People do lose weight on high-protein, low-carbohydrate diets, though the weight loss is due to water loss and reduced calories, not to lower insulin levels as the authors claim. Even so, nutrition experts do not recommend these diets. First, the weight loss is difficult to maintain over the long term. Second, there is some evidence that these diets may increase the risk of coronary heart disease (CHD) and kidney damage—conditions for which people with diabetes are already at high risk.
Weight Loss Is Difficult To Maintain
High-protein, low-carbohydrate diets may produce greater weight loss than other diets. But this weight loss is mostly water—rather than fat—and weight is quickly regained when you go off the diet. Why? A decreased intake of carbohydrates depletes carbohydrate stores in your body, and the water associated with these stores is released from the body. When you start eating carbohydrates again, the water returns. In addition, because high-protein, low-carbohydrate diets restrict food choices, people cannot follow these diets for long periods of time, and the lost weight is ultimately regained.
Increased Risk of Coronary Heart Disease
Diets high in protein tend to be high in fat, particularly saturated fat. For example, the Atkins diet and Protein Power provide about 20% to 25% of calories from saturated fat. In comparison, the American Diabetes Association recommends that less than 10% of calories come from this type of fat.
Diets high in saturated fat can raise blood cholesterol levels, which in turn increase the risk of CHD. In a study of the Atkins diet, published in the Journal of the American Dietetic Association in September 1980, people who followed the diet for eight weeks experienced an increase in blood cholesterol levels, even though they had lost weight. (Weight loss is known to decrease cholesterol levels.) In a more recent study in the October 2000 issue of the Journal of the American College of Nutrition, researchers calculated that long-term use of the Atkins diet would result in a 25% increase in blood cholesterol levels, which translates to an increased risk of CHD of more than 50%.
High-protein, low-carbohydrate diets can also increase your risk of CHD because they tend to be low in fiber, owing to the restrictions on fruits, vegetables, and grains. While the American Diabetes Association recommends 20 to 35 g of fiber per day, the Atkins diet and Protein Power supply only 5 to 10 g. Research shows that foods high in soluble fiber, such as oat bran, legumes, and apples, can decrease cholesterol levels and protect against CHD.
Increased Risk of Kidney Dysfunction
The American Diabetes Association recommends that people with diabetes consume no more than 20% of calories from protein. High-protein, low-carbohydrate diets exceed these recommendations: Protein makes up 35% of the calories in the Atkins diet and Protein Power, and 28% of the calories in Sugar Busters and The Zone. Such high levels of protein may increase the risk of kidney damage in people with diabetes and exacerbate existing kidney disease.
Another way that high-protein, low-carbohydrate diets may cause kidney problems is through a process called ketosis. Ketosis, which occurs when you do not eat enough carbohydrates, results in the production of acidic substances known as ketones that may build up in the bloodstream in people with type 1 diabetes. This can lead to a diabetic emergency known as diabetic ketoacidosis.
The Best Weight Loss Plan
The best way to lose weight—and to keep it off—is not to look for a "quick fix" but to make lifestyle changes that involve reducing the total number of calories you eat while increasing your level of physical activity. Remember, it is excess calories, not excess carbohydrates, that make you fat.
So eat a variety of foods to ensure that you get all the essential nutrients that your body needs. By choosing foods that are higher in carbohydrates and fiber and lower in fat, you can also improve blood glucose control and decrease your risk of CHD and kidney damage.