"The Institute of Medicine has established ranges for the percentage of calories in the diet that should come from carbohydrate, protein, and fat. These Acceptable Macronutrient Distribution Ranges take into account both chronic disease risk reduction and intake of essential nutrients. To manage body weight, Americans should consume a diet that has an appropriate total number of calories and that is within the recommended ranges. Strong evidence shows that there is no optimal proportion of macronutrients that can facilitate weight loss or assist with maintaining weight loss. Although diets with a wide range of macronutrient proportions have been documented to promote weight loss and prevent weight regain after loss, the critical issue is whether the eating pattern is reduced in calories and whether the individual is able to maintain a reduced-calorie intake over time. The total number of calories consumed is the essential dietary factor relevant to body weight. In adults, moderate evidence suggests that diets that are less than 45 percent of total calories as carbohydrate or more than 35 percent of total calories as protein are generally no more effective than other calorie-controlled diets for long-term weight loss and weight maintenance. Recommended macronutrient proportions are 45–65 percent carbohydrate, 5–20 percent protein, and 30–40 percent fat for young children ages 1–3; 45–65 percent carbohydrate, 10–30 percent protein, and 25–35 percent fat for older children and adolescents ages 4–18; and 45–65 percent carbohydrate, 10–35 percent protein, and 20–35 percent fat for adults age 19 and older."