Here is what happens

You eat a chocolate and sugar is released into your bloodstream. Your pancreas detects a flurry of sugar and releases a hormone called insulin. Insulin sends the troops in to regulate the sugar by storing it as glucose in the liver and muscles and any excess sugar is stored in the fat cells. The more sugar you eat the more insulin is released. When the body battles to regulate the sugar by releasing too much insulin too fast, you tend to get a drop in blood sugar levels and then you get the crash called hypoglycaemia. That point of no return where you can barely keep your eyes open any more. You feel like you just need to have a power nap.