A baby is born with a very high requirement for energy and nutrient intake per unit of body weight to provide for rapid growth. An adult individual needs to balance energy intake with his or her level of physical activity to avoid storing excess body fat . As teenagers reach adulthood, the basal energy needs for maintaining the body’s physiological functions ( basal metabolic rate , or BMR) stabilize, and so energy requirements also stabilize. Physical activity, especially weight-training exercises, help increase and maintain lean body mass.
Obesity is a risk factor for other degenerative diseases, such as type II (adult onset) diabetes, diseases of heart and circulation, and certain cancers. It is believed that the changes in body composition and reduced lean muscle mass occur at a rate of about 5 percent per decade, and energy requirements decrease accordingly. However, these changes in body composition and decreased energy requirements can be prevented by maintaining regular physical activity, including resistance training, which helps maintain lean muscle mass and prevent deposition of excess body fat.
Good health requires adults to adapt their diets to the body’s changing needs by eating low-fat and nutrient-rich foods.
By preventing normal age-related decline in lean muscle mass, one can prevent obesity and prolong one’s physiological age. Older adults who are not physically active or who have poor nutritional practices will have a decline in BMR, a change in body composition, an increasing percentage of body fat, and a decrease in lean body muscle mass. As women age, they may develop osteoporosis if they have not built up strong bones by eating foods high in calcium and adequate vitamin D .