If you really want to do something, you'll find a way.  If you don't, you'll find an excuse.

Metabolism and Energy

Basal metabolism is the process in which energy is produced by the body. The amount of energy used by the body at rest is called the basal metabolic rate, or the BMR. About 60 to 70 percent of the energy used by your body during the day is to maintain the body's systems, such as digestion of food, beating of the heart, breathing, maintaining body temperature, and many other life-sustaining functions. If you consume more calories than needed for basal metabolism, you will need to burn these calories off with some form of physical activity.

Several factors determine the basal metabolic rate. Age is the one of most influencing factors; generally, the younger you are, the higher your BMR. This is due to the fact that during infancy and childhood there are many growth spurts requiring high amounts of calories. After you reach 30, your BMR slows down by a rate of one to two percent a year. It becomes increasingly harder to lose and keep weight off as you grow older. The "middle-age spread" is often a result of a slowing of the BMR and an inclination to be inactive.

Another significant factor is the influence of your body composition. Muscle tissue is highly active even at rest. The more muscle tissue in your body, the higher your BMR. Men usually have a higher BMR because of their greater tendency toward lean muscle tissue.

Hormones also play an important part in basal metabolism. The BMR is likely to change during puberty and pregnancy due to hormonal changes. Many women also find themselves gaining weight around menopause. It's not unusual for a woman to gain ten or fifteen pounds even though she may not have increased her calories or decreased the amount of daily exercise. This weight gain may be nature's attempt to protect her. The extra padding around the hips can help to prevent injury due to falls. Small amounts of estrogen created by the fat cells can help to replace the estrogen no longer produced by the ovaries. Also, the extra weight provides a natural weight bearing exercise to make the bones denser helping to prevent osteoporosis. 

If obesity is not a factor, then the weight gain may not be harmful. Overall fitness is the key to wellness and is extremely important.

Tony Chemer