Getting the Skinny on High Protein Diets

by Martha McKittrick, RD, CDE

Take a walk through your local bookstore and you will be bombarded with high-protein diets. Bacon and eggs for breakfast. Fried chicken for dinner. Eat all the cheese and steak you want.

Most of these diets allow unlimited quantities of fat and protein, but do not allow carrots or potatoes. In addition to promoting weight loss, such diets claim that they will improve your health by lowering cholesterol, blood pressure, and risk for diabetes. Sound too good to be true? It is!

High-protein diets are the rage now, having made a comeback from their heyday in the 1960s and 70s. The diet pendulum seems to swing from low-fat, high-carbohydrate to high-protein, low-carbohydrate. Low-fat, high-carbohydrate diets were popular until many people realized that they were gaining, not losing weight. But the real reason for the weight gain was that, in our obsession with avoiding fat, we overloaded our diets with fat-free foods, often in over sized portions and, although low in fat, they were still full of calories from other sources. As a result, a backlash against carbohydrates has occurred and the pendulum has swung back to high-protein diets. What are these diets all about? Do they actually promote weight loss? Are they safe?

All About High-Protein Diets

The major claim behind most high-protein diets is that insulin (a hormone that regulates blood sugar), not calories, makes you fat. The argument is that carbohydrate-containing foods turn to sugar and drive up insulin levels, and these high insulin levels promote fat storage, increase hunger, and cause diseases such as high blood pressure and heart disease. The rationale behind high-protein diets is that eating minimal amounts of carbohydrates will prevent higher insulin levels.

Insulin resistance

In reality, insulin is a hormone that is needed for the transfer of sugar out of the blood and into the cells, where it is used for energy. Insulin also transfers fat and protein out of the blood and into the cells. The majority of people do not secrete excess insulin in response to eating a moderate sized portion of carbohydrates. However, it is true that about 25 percent of the population is insulin-resistant. In insulin-resistant individuals, cells are not very sensitive to the effects of insulin, and therefore, these people produce excess insulin. Genetics and environmental factors such as obesity, physical inactivity, and aging, play a role in insulin resistance.

In addition to losing weight and exercising, people with insulin resistance may benefit from decreasing their intake of refined carbohydrates or carbohydrates with a high glycemic index -- that is, foods that contain a high level of glucose. (For example, white bread has a higher glycemic index than 7-grain bread). Foods with a high glycemic index turn to sugar more quickly than foods with a lower glycemic intake, and this, in turn, causes a greater secretion of insulin. You can also lower the glycemic index of a carbohydrate-containing food by adding protein and/or fat.

But keep in mind that the majority of people do not have insulin resistance and will not secrete excess insulin in response to eating carbohydrates. So insulin is not the culprit in obesity or fat storage. Think about it. If a high-carbohydrate diet makes you fat, why are the Japanese, who eat the bulk of their calories in the form of rice and grains, not overweight?

Do High-Protein Diets Promote Weight Loss?

High-protein diets do promote weight loss. The weight loss, however, is often temporary. There are two major explanations for the loss:

• High-protein diets cause dehydration, which will show up as weight loss -- usually immediate and often dramatic -- on the scale. A quick lesson in physiology will explain how this happens. Carbohydrates are the major energy source for our bodies. We store carbohydrates in the form of glycogen. Each glycogen molecule is bound to three molecules of water. As you reduce the intake of carbohydrates in your diet, your body starts using up glycogen stores for energy and, in the process, it releases the water that was bound to the glycogen.