I got this here from the Mayo Clinic.
Slow metabolism: Is it to blame for weight gain?My sister says that she's overweight because she has a slow metabolism. Is there such a thing?
from Donald Hensrud, M.D.
Yes, there is such a thing as a slow metabolism. But it's rare, and it's usually not what's behind being overweight or obesity — that's usually a matter of diet and exercise.
Metabolism is the process by which your body converts what you eat and drink into energy. Even when you're at rest, your body needs energy for functions such as breathing, circulating blood and repairing cells. The number of calories your body uses for these basic functions is known as your basal metabolic rate (BMR).
Several factors determine your basal metabolic rate:
■Your body size and composition. If you're larger or have more muscle mass, you will burn more calories, even at rest. (So overweight people are more likely to have a faster metabolic rate — not a slower one.)
■Your sex. If you're a man, you probably have less body fat and more muscle mass than a woman of the same age, so you burn more calories.
■Your age. As you get older, your muscle mass decreases, which slows down the rate at which you burn calories.
Rather than metabolism, factors more likely to contribute to weight gain include:
■Eating too many calories
■Getting too little exercise
■Genetics and family history
■Unhealthy habits, such as skipping breakfast or not getting enough sleep
If you're concerned about your weight, talk with your doctor about healthy changes you can make. And if you still think your metabolism is too slow, your doctor can check it or check for rare conditions that can cause problems with metabolism, such as hypothyroidism and Cushing's syndrome.