High-protein, low-carbohydrate diets have been widely promoted in recent years as an effective approach to losing weight. These diets generally recommend dieters receive 30% to 50% of their total calories from protein. By comparison, the American Heart Association, the National Cholesterol Education Program, and the American Cancer Society all recommend a diet in which a smaller percentage of calories are derived from protein (nutrients essential to the building, maintenance, and repair of tissues in the body).

The Atkins diet is an example of a high protein, low carbohydrate diet.

How Do These Diets Work?

By restricting carbohydrates drastically to a mere fraction of that found in the typical American diet, the body goes into a different metabolic state called ketosis, whereby it burns its own fat for fuel. Normally the body burns carbohydrates for fuel -- this is the main source of fuel for your brain, heart and many other organs. A person in ketosis is getting energy from ketones, little carbon fragments that are the fuel created by the breakdown of fat stores. When the body is in ketosis, you tend to feel less hungry, and thus you're likely to eat less than you might otherwise. However, ketosis can also cause health problems, such as kidney failure (see below).

As a result, your body changes from a carbohydrate-burning engine into a fat-burning engine. So instead of relying on the carbohydrate-rich items you might typically consume for energy, and leaving your fat stores just where they were before (alas, the hips, belly, and thighs), your fat stores become a primary energy source. The purported result is weight loss.

What Are the Health Risks Associated With High Protein, Low Carb Diets?

High protein diets can cause a number of health problems, including:

• Kidney failure. Consuming too much protein puts a strain on the kidneys, which can make a person susceptible to kidney disease.
• High cholesterol. It is well known that high protein diets (consisting of red meat, whole dairy products, and other high fat foods) are linked to high cholesterol. Studies have linked high cholesterol levels to an increased risk of developing heart disease, stroke and cancer.
• Osteoporosis and kidney stones. High protein diets have also been shown to cause people to excrete more calcium than normal through their urine. Over a prolonged period of time, this can increase a person's risk of osteoporosis and kidney stones.
• Cancer. One of the reasons high protein diets increase the risks of certain health problems is because of the avoidance of carbohydrate-containing foods and the vitamins, minerals, fiber and anti-oxidants they contain. It is therefore important to obtain your protein from a diet rich in whole grains, fruits and vegetables. Not only are your needs for protein being met, but you are also helping to reduce your risk of developing cancer.
• Unhealthy metabolic state (ketosis). Low carb diets can cause your body to go into a dangerous metabolic state called ketosis since your body burns fat instead of glucose for energy. During ketosis, the body forms substances known as ketones, which can cause organs to fail and result in gout, kidney stones, or kidney failure. Ketones can also dull a person's appetite, cause nausea and bad breath. Ketosis can be prevented by eating at least 100 grams of carbohydrates a day.