When you drink a can of diet soda, your brain thinks you just stumbled across a wild blueberry bush, and it sends urgent signals to eat large and eat fast before someone else gets wind of your bounty. At the same time, your body knows that if you eat too many calories, you might get too fat and not be able to outrun that saber-toothed tiger, so when your gut senses that you’ve absorbed enough calories, it sends signals up to your
