Carbohydrate and Protein Intake

In the past, hypocaloric diets to promote weight loss in the obese patient focused mainly on reducing total fat or saturated fat intake. More recently, interest has shifted to the role that dietary carbohydrates and protein play in the weight loss diet. Emerging research is suggesting that a higher protein intake, as well as a shift from simple to complex carbohydrates, with an increased intake of dietary fiber, may be a more practical approach for weight loss and weight management.

Some regimens like the Atkins Diet shun carbohydrates, but many “carbs” may be beneficial for weight loss and maintenance.

Carbohydrates are the preferred source of energy in the human diet, yielding about four calories per gram. They are usually classified into two categories, which include simple and complex forms. Simple carbohydrates include sugars, while complex carbohydrates include starches and fiber. Some evidence suggests that eating pattern changes may be one of the causes for the increased prevalence of obesity. These eating pattern changes are characterized especially by the increase in the dietary intake of simple sugars, such as sucrose and high-fructose corn syrup [Page 111]and refined grain products, along with a decreased intake of fiber.

Increasing the intake of fiber-rich carbohydrates, such as whole grains, beans, fruits, and vegetables, may be beneficial in the treatment of obesity. Fiber differs from simple sugars and starches because our body cannot digest it. Because dietary fiber does not provide any calories to the diet, a meal that is high in fiber is usually less energy dense. This may bring on a feeling of satiety due to the added bulk and slower absorption from the indigestible plant materials. Many fiber-containing foods are also rich in micronutrients such as vitamins, minerals, and phytochemicals, which may be of benefit as well. Additionally, fiber has been shown to lower blood cholesterol levels and insulin secretion, and to prevent and manage constipation and diverticulosis, which are complications often associated with obesity.

Similar to carbohydrates, protein yields about four calories per gram. Protein is an essential nutrient needed for growth and development, and is a component of virtually every living cell in the human body. Proteins are composed of amino acids, of which nine are essential, meaning that they cannot be synthesized in the body, and have to come from food sources. Proteins in food that supply all of the essential amino acids are called complete proteins. Most complete proteins come from animal sources, with soy being the only plant-based complete protein.

Recent research suggests that an increase in dietary protein intake may be beneficial in weight loss and weight management. Higher protein diets increase satiety and may increase the obese patient's adherence to a hypocaloric diet. Higher protein diets may also lead to a higher percentage of fat loss, spare muscle tissue during weight loss. In dietary practice, a shift to replace some simple and refined carbohydrates in the diet with high-quality, complete sources of protein that are low in saturated fat may be beneficial.

As part of a healthy lifestyle, a diet for weight management should focus on a low intake of simple sugars and refined carbohydrates, and a high intake of high fiber complex carbohydrates such as whole-grain products, vegetables, and beans. Currently, most American adults are consuming less than half of the recommended dietary fiber intake of 20 to 35 grams per day. Americans are receiving about 15 percent of their dietary energy each day as protein, which is considered adequate. Most studies that focus on moderately high protein intake for weight loss and maintenance suggest about 30 percent of the daily caloric intake should come from protein. The role of higher protein diets to promote weight loss is generally well accepted; however, their longer-term role in weight management is not clear because studies investigating their safety and efficacy have yet to be reported.

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