Test Your Knowledge

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.