Factors Contributing to Obesity:
Energy-dense foods are a major factor driving obesity in the U.S. While the term “energy density” may sound odd when applied to foods, it should be remembered that a calorie is a unit of energy, not of weight or fat. Energy density is measured as the number of calories per gram, or the amount of energy contained in a given weight of food.
Foods with large amounts of water and fiber tend to have low energy densities, and as such are low in calories
Water and fiber both play a large role in determining energy density. Foods with large amounts of water and fiber, such as fruits and vegetables, tend to have low energy densities, and as such are low in calories (Exhibit 7). Research suggests that food volume plays a greater role in causing people to feel full than calorie intake. Because fruits and vegetables typically supply fewer calories for the same amount of volume, they can impart a feeling of fullness on far fewer calories. Individuals who want to decrease their daily calorie intakes thus can substitute fruits and vegetables for more energy-dense foods.37
A 2005 survey of fruit and vegetable consumption in the U.S., however, found that fewer than a third of U.S. adults surveyed consumed fruit at least twice per day, and only 27.2 percent consumed vegetables at least three times per day as recommended.38
Increasing the availability and consumption of vegetables and fruits could reverse the trend towards more high-calorie, energy-dense foods in daily diets, and thus help reduce the incidence of overweight and obesity.
Energy Densities of Common Foods (calories per gram)
Apple with skin
Broccoli, raw, flower clusters
Baked Chocolate Chip Cookies (from refrigerated dough)
Double, large-patty cheeseburger with condiments & vegetables (fast food)
Drumstick, breaded and fried
Source: National Institutes of Health.
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- 37 National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition, Physical Activity and Obesity, “Low-Energy-Dense Foods and Weight Management: Cutting Calories While Controlling Hunger,” Research to Practice Series (No. 5), pp. 1-2, and “Can Eating Fruits and Vegetables Help People to Manage Their Weight,” Research to Practice Series (No. 1), p. 1, (Last visited January 7, 2011.)
- 38 U.S. Centers for Disease Control and Prevention, “Fruit and Vegetable Consumption Among Adults-United States, 2005,” MMWR Weekly (March 16, 2007), pp. 213-217, and U.S. Department of Health and Human Services and U.S. Department of Agriculture, Dietary Guidelines for Americans, 2005, 6th ed. (Washington, D.C., January 2005), p. 24, (Last visited January 7, 2011.)