Assuming you're not diabetic or prone to hypoglycemic episodes, another way to keep your body guessing is to restrict carb intake (about 50 grams per day) for 48 hours every two or three weeks. Your body will search for alternate energy sources, breaking its rhythm and revving the metabolism. Because it has been glycogen-depleted, your body will quickly use sugar carbs for energy when you return to taking in normal levels.

Do not go low-carb for more than a couple of days or take in fewer than 125 grams per day. Critical heart and brain functions rely on carbs. Depleting sugar stores can make you lethargic, foggy-headed and, yes, even hangry, so try this phase on weekends when you don't have to deal with workweek stressors like deadlines and demanding coworkers. When you do wants carbs—the good kind—reach for one of The Top 50 Snacks for Weight Loss.