Slow metabolism: Is it to blame for weight gain?

My sister insists that she is overweight because she has a slow metabolism. Is there such a thing?

- No name / No state given

Answer

Yes, there is such a thing as a slow metabolism. But it's rare. The bottom line is: Most overweight or obese individuals do not get that way because of a slow metabolism. They get that way because they eat too many calories and don't exercise enough.

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 truly have a slow metabolism — which means they burn fewer calories at rest than they should according to estimates based on their height, weight, age and sex. In fact, people who are overweight usually have an increased metabolic rate because they have more muscle as well as fat.

It's true that your metabolism slows slightly as you get older. So you may need to decrease your calorie intake or increase your physical activity as you age.

If you're concerned that you have a slow metabolism, talk to your doctor. Your doctor may recommend a test to calculate your BMR, or resting energy expenditure. Medical conditions that can decrease BMR or alter your muscle-to-fat ratio include hypothyroidism and Cushing's syndrome. A doctor can test for such conditions.

MORE ON THIS TOPIC

• Hypothyroidism (underactive thyroid)
• Cushing's syndrome

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