if you drink a glass of water with three tablespoons of sugar (similar to what would be in a can of soda), you’ll have a big spike in your blood sugar levels within the first hour. That causes your body to release so much insulin to mop up the excess sugar that you actually overshoot and become hypoglycemic by the second hour, meaning that your blood sugar drops even lower than it would if you were fasting. Your body detects this low blood sugar, thinks you might be in some sort of famine situation, and responds by dumping fat into your bloodstream as an energy source to keep you alive.