Slow metabolism: Is it to blame for weight gain?
Medically reviewed by Drugs.com. Last updated on Feb 21, 2019.
Probably not. Although there is such a thing as a slow metabolism, it's rare. And it's usually not what's behind being overweight or obese — that's ultimately a result of interactions among genetics, diet, physical activity and other factors.
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 energy your body uses for these basic functions is known as your basal metabolic rate.
Several factors determine your basal metabolic rate:
- Body size and composition. If you weigh more or have more muscle mass, you'll burn more calories, even at rest. So people who weigh more are more likely to have a faster basal metabolic rate — not a slower one — because a portion of excess weight is muscle tissue.
- Sex. Men tend to have less body fat and more muscle mass than women of the same age and weight. Again, higher muscle mass means burning more calories.
- Age. As you get older, your muscle mass decreases, which slows down the rate at which you burn calories.
Rather than slow metabolism, factors more likely to contribute to weight gain include:
- Eating too many calories
- Getting too little physical activity
- Genetics and family history
- Certain medications
- Unhealthy habits, such as routinely not getting enough sleep
If you're concerned about slow metabolism and your weight, talk to your doctor about healthy changes you can make. And if you still think you have slow metabolism, your doctor can check your metabolism or check for rare conditions that can cause problems with metabolism and weight, such as an underactive thyroid (hypothyroidism), Cushing syndrome or polycystic ovary syndrome (PCOS).