Carbohydrate-limiting diets are an example of so-called “fad diets” that promise to help people shed weight simply by changing the types of foods they eat. Typically, people on carbohydrate-limiting diets are asked to switch to a high-protein diet rich in meats, cheese and other foods while avoiding fruits, vegetables, grains and other foods rich in carbohydrates.

However, experts stress that these diets do not work over the long run and are more likely to cause harm than to achieve good. Many people on carbohydrate-limiting diets do lose weight, especially initially when a lot of water weight is shed. However, weight loss tends to stop or reverse anywhere from six months to a year after beginning such a diet.

There are many myths that surround high-protein, low-carbohydrate diets. Proponents of these diets often recite these myths as though they were facts. People are urged to be cautious in accepting claims made by proponents of fad diets.

Experts stress that an excessive intake of calories (energy) causes weight gain, regardless of whether the source is protein, carbohydrates or fat. In addition, high-protein, low-carbohydrate diets tend to be very high in saturated fats and cholesterol, which increases the risk for many illnesses. Low-carbohydrate, high-protein diets also deprive the body of many nutrients that are essential to good health.

Carbohydrate-limiting diets are food regimens that supposedly help people to lose weight and keep it off through eating a diet that is high in protein and low in fruits, vegetables, grains and other foods. However, experts stress that these diets are not successful over the long run and are more likely to cause harm than to achieve good.

New fad diets emerge occasionally that promise to help even the most frustrated dieter shed weight. In recent years, these diets have focused on eating a high-protein, low-carbohydrate diet. In general, the body gets calories (energy) from three nutrients – protein, fats and carbohydrates. The latter two nutrients provide most of the calories in the average person’s diet.

Proponents of the high-protein, low-carbohydrate diets sometimes suggest that eating such foods prevents weight gain because of both lower calorie intake, and because the protein in the foods goes straight to a person’s muscles rather than turning to fat.

However, these claims contradict traditional nutritional knowledge. The body requires a certain number of calories to function properly. While excessive intake of calories does cause weight gain, any type of calorie in excess can be the cause. Most experts urge people to cut back their calorie intake by eating a well-balanced diet rather than by dramatically shifting their diet away from a whole nutrient group such as carbohydrates. In addition, carbohydrates contain many nutrients that are essential to good overall health, such as vitamins, minerals and fiber.

While high-protein diets help some people lose weight in the short-term, maintaining weight loss with this type of diet has not been successful for most people. In addition, high-protein diets present certain health risks.

Most experts continue to recommend a diet high in the right types of carbohydrates (e.g,, whole grains, fruits, vegetables) and low in high-fat foods (including high protein foods such as red meat and cheese) as the best way to maintain a healthy weight and reduce the risk of certain chronic illnesses.

Very often, people make nutritional claims on behalf of carbohydrate-limiting diets or other fad diets that cannot be proved. In some cases, proponents may manipulate information from legitimate research in a manner that appears to bolster their claims. However, time typically reveals these claims as unsupported.

There are many myths that surround high-protein, low-carbohydrate diets. Proponents of these diets often recite these myths as though they were facts. People are urged to be cautious in accepting claims made by proponents of fad diets.

Some proponents of low-carbohydrate diets contend that sugars and starches are bad for people because they are absorbed easily and raise blood glucose levels. This causes the pancreas to secrete insulin, a hormonal substance that these critics deem responsible for causing weight gain. In truth, insulin is just one of many factors involved in the metabolism of nutrients and regulation of body weight. Appropriate levels of insulin are essential for the body to gain energy from nutrients. Problems such as insulin resistance (condition in which the body’s cells are less responsive to insulin) can cause major health issues, but they are not caused by the consumption of carbohydrates.

Other advocates of these diets contend that high-protein foods increases energy production in the body. While this may be technically true, the difference in energy production when compared to carbohydrates or fats is so slight that it is insignificant.

People who consume high-protein, low-carbohydrate diets have differing results. Many people do lose weight, especially at first. In fact, a recent government-funded study found that a low-carbohydrate, high-protein diet caused the most weight loss of four popular diet plans that were tested.

However, many experts warn that the weight loss attributed to low-carbohydrate diets tends to result from the diuretic effect of a high-protein diet, which causes loss of water weight, not fat loss. This lost weight often returns again later, and the effectiveness of high-protein, low-carbohydrate diets is typically temporary.

People also may lose weight on high-protein diets simply because a lack of carbohydrates eliminates many calories from their diet. For example, a steak has fewer calories if it is not combined with a potato and sour cream and butter. High-protein meals also tend to leave people feeling more full (satiated), because protein is the most satiating nutrient. Finally, these diets offer a plan for people to follow, and structuring eating plans facilitates weight loss.

In addition, high-protein, low-carbohydrate diets tend to be very high in saturated fats and cholesterol, which increases the risk for heart disease, high blood cholesterol and other illnesses. As a result, people who switch to a low-carbohydrate diet are urged to include a lot of vegetable sources of fat and protein.

Excessive levels of protein also have been associated heart disease, kidney disorders, kidney stones, obesity and some forms of cancer.

High-protein, low-carbohydrate diets also may cause ketosis, a metabolic state whereby the body burns fat for fuel instead of carbohydrates. This may result in increased blood ketones due to an incomplete breakdown of fat. While advocates of these diets contend that increased ketones helps reduce body fat and quicken weight loss, the only proven method for reducing body fat is physical activity. Ketosis suppresses hunger and is therefore likely to result in lower calorie intake. However, ketosis also causes a number of problems, including breaking down muscle, and developing weakness, fatigue, nausea, dehydration, light-headedness and irritability. It can be fatal for people with diabetes and may cause birth defects or fetal death when it occurs in pregnant women.

Other health problems that may be associated with high-protein diets include:

• Constipation and other gastrointestinal disorders associated with low-fiber diets
  
  
• Excessive leaching of calcium from the bones
  
  
• Strain on the liver and kidneys as the body struggles to break down the excessive protein

Finally, low-carbohydrate diets prevent the body from getting many nutrients that can only be found in carbohydrates. This includes fiber, vitamins, minerals and phytochemicals. Supplements can restore some of these nutrients, but these foods also contain health benefits that cannot be obtained from any supplement.

To date, there is no conclusive evidence that low-carb diets cause greater weight loss, despite some recent studies that appear to corroborate the claims made by the proponents of these diets. In fact, one recent Australian study found that diets high in carbohydrates that nonetheless rank low on the glycemic index (which measures how rapidly certain foods are converted to blood sugar) actually promote weight loss while also reducing both body fat stores and cardiovascular disease risk.

Preparing questions in advance can help patients have more meaningful discussions with health professionals regarding their conditions. Patients may wish to ask their doctor or registered dietitian the following questions related to carbohydrate-limiting diets:

1. What are the health risks posed by a carbohydrate-limiting diet?
   
   
2. How do I know if I have the proper balance of carbohydrates, fats and proteins?
   
   
3. Is there someone who can help me plan a well-balanced diet?
   
   
4. What is the best way for me to achieve weight loss?
   
   
5. Who can help me get started on an effective exercise program?
   
   
6. I have insulin resistance. Should I switch to a low-carbohydrate diet?
   
   
7. I’m on a low-carbohydrate diet. Should I take supplements?
   
   
8. How can I reduce the health risks associated with a low-carbohydrate diet?
   
   
9. Will I need to be monitored by a physician while I’m on this type of diet?
   
   
10. What foods will I especially need to avoid?