Typically, a loss of muscle mass, accompanied by a gain in fat mass, occurs with aging.  However, researchers at the University of Arkansas for Medical Science have found that we can control our metabolic rate and thereby improve our physique as we age.  The singlemost important determinant of metabolic rate is lean body mass. 

The more lean tissue you have, the higher your metabolic rate: put simply, an active body is too busy processing calories to store extra as fat.   Strength-training exercises can raise our metabolic rate by about 30-50 calories per day, and over the course of three months of strength-training that is appropriately designed for your needs, you can gain about 3 pounds of muscle, amounting to a total boost in the basal (resting) metabolic rate of 7%.