4. You get horrible headaches.
Your brain runs on the glucose found in your blood, and the glucose in your blood comes from the carbohydrates you eat. Limit your calories and carbs too much, and your brain will become energy-starved. Feeling shaky, dizzy, or light-headed—or getting otherwise unexplainable headaches—are signs you’re not eating enough, and your blood sugar has dropped too low. Simply adding more calories and carbs to your diet should stop your head from pounding—and help the pounds come off more rapidly, too.