Macronutrients -- the big three of protein, carbohydrates and fat -- are the cornerstone of any dietary plan. The U.S. Department of Agriculture notes that all three are important to your health, but balance is important. The best ratio for you depends on age.
Age Affects Recommendations
Young children need extra fuel to grow, which means they should have more fat than older children, adolescents and adults, according to the USDA. Children 1 to 3 years old should have a diet that contains 45 percent to 65 percent carbohydrate, up to 20 percent protein and 30 percent to 40 percent fat. From age 4 to 18, the percentage of carbohydrate stays the same, but protein increases to as much as 30 percent of the diet, while fat should be not more than 35 percent of the diet. The proportion of carbohydrate is also the same for adults, but protein should be 10 percent to 35 percent of the total food intake, and fat should be 20 percent to 35 percent.