Aging, leads to decrease in muscle mass as a result of a fall in activity levels and thus your energy requirements are less. In addition, many of your daily activities change: you don’t run to catch that bus anymore, you now play half court basketball instead of full court, and you may have exchanged the salsa for the tango.
With aging, it’s also more difficult to take off those additional pounds around your waist or hips. It is easy to take off the pounds at age 25 but at 50, it takes real work to get that zipper closed again.
Besides, the lessened energy needs with aging are not matched by a parallel decline in food consumption and, as a result, your body fat increases. If you saw an MRI of how the average thigh changes with aging, you would be shocked. The size of your thigh bone, the femur, doesn’t change much. In the young thigh, the muscles comprise most of the cross-section of the thigh. But, if you don’t stay in shape, by the time you reach old age, you will have a hard time finding the muscle mass that has shrunken to a small fraction of its young size.
Studies conducted over age weight and height of individuals at death (compiled over the years by insurance companies researching life insurance rates) clearly indicate that the longest lived group are those in the middle weight categories and that those who were at the two extremes, the very underweight and the very overweight, had the shortest time on this planet.
Later in life, having a few extra pounds may even improve your health and longevity. In a study of individuals in their seventies, those with the best chances of survival had BMI’s that were 25-27 kg/m (women). One of the interesting discoveries in aging research is that pounds that are added to your hipsare not as detrimental to your health and longevity as pounds added to your waistline. All the evidence shows that it’s better to resemble a pear than an apple. The pear-shaped figures of the women probably did not cause them any serious health problems. However, the massive beer bellies carry with them a significant health risk.