A person's healthy weight range remains the same as a person gets older; however, caloric needs may change as metabolism slows down and activity reduces, according to Everyday Health. An adult's body mass index, or BMI, indicates if he is in a healthy weight range.
BMI is calculated using a person's weight and height, states Everyday Health. Online calculators and charts also show underweight, overweight and obese BMI ranges. Individuals over the age of 50 may have difficulty maintaining a healthy weight and may need to reduce the number of calories they consume relative to the level and duration of exercise they get.