As you age, your metabolism slows so that you need fewer calories than you did when you were younger. Each decade after age 20, your daily energy needs may decrease by as much as 150 calories, according to the American Council on Exercise. For optimal nutrition, get your calories from healthy foods such as fruits, vegetables, fish, nuts, reduced-fat dairy and whole-grain bread.
Your exact calorie needs depend on your weight, activity level and body composition; for example, people who have more muscle tissue need more calories than those who have more fat. On average, however, a moderately active woman over 70 needs about 1,800 calories per day, while a moderately active man over 70 needs about 2,200 calories per day. A sedentary woman in that age group only needs 1,600 calories per day, while a sedentary man needs about 2,000 calories per day. By definition, a moderately active lifestyle includes the equivalent of walking 1.5 to 3 miles per day, while a sedentary lifestyle includes only the activities necessary for everyday life, such as cooking and walking to the restroom.