Slow metabolism: Is there any such thing?

Yes, there is such a thing as slow metabolism. But it is uncommon. Most overweight individuals are not overweight because of a slower than average metabolism but because they eat too many calories and don't get enough exercise.

Metabolism is the complex biochemical process by which the food you eat is converted into the energy your body needs to function. Basal metabolic rate (BMR) is the amount of calories you burn at rest.

Your body composition is one of the primary factors that determine BMR. The more lean muscle you have, the more calories you burn. This is why men — who typically have more lean muscle than women do — tend to lose weight faster and gain it more slowly. It's also why experts recommend strength training to build muscle mass.

BMR is also affected by how much you exercise. All physical activity, not just strenuous activity, increases the number of calories you burn.

Only a small number of people burn fewer calories at rest than they should, according to estimates based on their height, weight and age. Because people who weigh more have more muscle as well as fat, overweight people usually have an increased metabolic rate, contrary to popular belief.

Your metabolism slows somewhat with age. So you may need to decrease your calorie intake or increase your physical activity accordingly. Also, some medical conditions — such as hypothyroidism and Cushing's syndrome — can decrease BMR or alter your muscle-to-fat ratio. A doctor can test for these conditions.