“If too little glucose is available in your blood, which is what happens when you follow a low - carbohydrate diet, then your liver hoards glucose so that your brain, which needs glucose to function, doesn't starve. While your body will start to break down fat to use as fuel, your brain can't run that way for long, and it will send out the Bat-Signal for more calories. That's the reason why when you skip a meal or go too long between meals, you find yourself running to the nearest donut or bag of chips.”