Obesity: Nutritional Considerations

The Western diet, which emphasizes highly energy–dense foods rich in fat and sugar, promotes overconsumption and weight gain.

The best strategy for permanent weight control is to change the type of foods you eat and increase physical activity. When foods lower in energy density and higher in water and fiber (e.g., salads, soups, vegetables, and fruits) are consumed instead of foods high in energy density, early fullness occurs, along with decreased food intake. This strategy has produced weight loss in several clinical studies.

The following steps reduce the energy density of the diet and promote weight control:

• Reducing dietary fat: Fat contains more than twice as many calories as protein and carbohydrate (9 calories per gram of fat, compared with 4 for protein or carbohydrate). Dietary fat often results in overconsumption of calories. The addition of fats to meals results in fat storage rather than fat burning. These mechanisms may explain why the prevalence of overweight individuals worldwide is directly related to the percentage of fat in the diet, and why low–fat diets have been consistently shown to promote moderate weight loss. Common sources of fat are meats, dairy products, fried foods, and added oils.
• Choosing foods high in complex carbohydrates and fiber: Populations in Asia, Africa, and elsewhere whose diets are high in complex carbohydrates tend to have a low incidence of obesity. The whole grains and legumes in these diets also provide fiber. Fiber is filling, but contributes little to overall calorie intake. Studies show that fiber intake is inversely associated with body weight and body fat (i.e., individuals who eat the most fiber tend to have better weight control, and vice versa).
• Following low–fat, vegetarian diets: Many studies have found that vegetarians tend to be slimmer than individuals who eat meat, which is not surprising given that grains, legumes, vegetables, and fruits are low in fat and high in complex carbohydrate and fiber. Randomized trials show that low–fat vegan diets promote greater weight loss than typical low–fat diets, and they also improve cholesterol levels and blood sugar. A study of a vegetarian diet in heart patients, used in combination with exercise and stress management, showed sustained weight loss over a five–year period.
• Minimizing sugars: Sucrose, high–fructose corn syrup, and other sugars add calories without producing fullness. In particular, an increasing intake of sweetened beverages is strongly associated with a rise in obesity.

Low–carbohydrate diets, such as Atkins and South Beach, are not recommended. They have not been found to be superior to either low–fat, high–carbohydrate, or calorie–controlled diets over a 12–month period. Further, these types of diets have been shown to increase cholesterol levels, particularly LDL (the “bad”) cholesterol, sometimes severely, in approximately one–third of users. They can also cause calcium loss from the body.

Certain personality and behavioral factors are characteristic of those who succeed at maintaining weight loss. These factors include developing coping skills that prevent using food for comfort; engaging in high levels of physical activity (approximately one hour per day); eating a low–calorie, low–fat diet; eating breakfast regularly; self–monitoring weight on a regular basis; and maintaining a consistent eating pattern through the seven–day week. The characteristic behaviors of those who keep weight off are documented and updated through the National Weight Control Registry, available at: http://www.nwcr.ws/.