Losing weight, then gaining it back, losing it again, and gaining it back ... it's a vicious cycle that can really do a number on your body. Yo-yo dieting isn't good for your physical health -- or your emotional health. You can put a stop to the yo-yo madness once and for all. The key is understanding why it happens in the first place. Here are just a few of the ideas from AOL Body:

• You underestimate the power of sugar. High-sugar foods like refined carbs make your blood sugar spike and trigger a release of hormones that can make you feel more hungry and crave certain foods.
• You lie to yourself. You tell yourself that one indulgence won't hurt. And it won't! The problem starts when one indulgence turns into two, three, four, five, or more.
  
• You think in days. If you slip and allow yourself a treat or miss your exercise session you think "well, today's a bust ... I'll start again tomorrow." Don't let one slip mess up an entire day.

Be sure to check out the AOL Body slideshow to learn more about yo-yo dieting.