When you exercise with a low fuel supply, your body panics and starts releasing massive amounts of stress hormones.
These stress hormones shut your thyroid down and lower your metabolism to conserve and save what little fuel you do have to keep your brain functional.
If your body didn’t shut everything down, then you would burn through all your fuel quickly, your brain would stop functioning, you would lose consciousness, and death would soon follow.
It’s simply a natural survival mechanism.
Yet, the effects of exercising on an empty fuel tank have long-lasting effects on your thyroid and metabolism.
This means that your body starts burning calories at a very slow rate. Not just while you exercise, we’re talking about 24 hours a day, 7 days a week, which only leads to long-term weight gain.