Has Exercise Suppressed Your Basal Metabolism?

Most people are led to believe that exercise increases basal (resting) metabolic rate (BMR). Yet, this couldn’t be further from the truth. In numerous studies, conducted on athletes, strenuous exercise from as little as one week up to as long as one year had a negative correlation to thyroid function. Many of us know long-duration cardio can suppress metabolism, yet most are unaware that intense weight training can also lower thyroid function.

We have been led to believe, if we are BURNING more daily calories that our metabolism has increased. However, this increase has nothing to do with an increased BMR. It only has to do with increased energy expenditure from more work (exercise) and an increase in stress hormones.

Yes, you may burn a ton of calories during intense exercise sessions, but this is in response to a stressful activity and increased adrenaline and cortisol, not because your thyroid levels have increased. In fact, thyroid levels decrease while exercising. Thyroid levels recover to normal only when cortisol levels have decreased.

You see, when you push your body to work harder, especially without adequate rest and nutrition, it learns to become more efficient. Your body is always trying to balance it’s energy demands with it’s available fuel. If the demands increase-in the form of intense exercise, and the fuel is not available, your body adapts by lowering your BMR.

Does this mean you shouldn’t participate in intense exercise?

Of course not, intense exercise, especially weight training, has its place when you want to drop fat, increase strength and power, and increase athletic performance. Yet, if you are in the beginning stages of trying to heal a damaged metabolism, intense exercise may need to be put on the back burner until your health improves.

If you are healthy, intense exercise like heavy lifting, sprinting, or high-intensity training can be done successfully with good results. Still, all intense exercise should be done in a healthy state, in moderation (this will depend on the person), with enough recovery and rest AND a supportive diet to restore metabolic function.