What happens when you do not eat enough calories?

You will begin to get really bad headaches!

First your body burns all of its stored energy, in other Words, your excess fat. Then it begins burning your muscles, and you get weak and lose all muscle tone. The hair on your head loses it's sheen, and gets thinner.

If your body starts burning muscle, remember that your heart is a muscle, and your health is *greatly* at risk. If you don't eat enough calories, you eventually die.

You would lose weight. If it continued, the body would start breaking down stored fat, then protein (meaning the muscles) if this stage of starvation occurred.