Because we do not have any food to burn for energy during this time, our body burns our stored body fat for energy instead. (pathtofatloss.com)
After all, how can your body burn its stored body fat if you're eating at maintenance or over it. (pathtofatloss.com)
Sleep deprivation also causes elevated blood sugar without the introduction of foods which decreases our tolerance to carbohydrates making it harder for us to burn stored body fat as fuel. (onnit.com)