Losing weight is difficult, but maintaining weight loss once you’ve lost it can be the biggest challenge of all. There’s a theory as to why it’s so difficult to keep those pounds from coming back called the set-point theory. It’s the concept that your body tries to keep your weight within a certain range, and you have a pre-determined “ideal weight” based on genetics. With diet and exercise, you can go above or below this set point, but when you do your body makes adaptations to bring you back to where it thinks you should be. This is one explanation as to why people who lose weight have a hard time keeping it off. It may also account for weight loss plateaus.
Set-Point Theory: How Your Body Responds When You Lose Weight
When you first change your diet and start exercising, the weight comes off rather easily. The change in lifestyle habits “shocks” your body initially and your weight drops. You’ve probably heard the phrase, “It’s easy to lose weight. I’ve done it a thousand times.” This shows how much easier it is to lose weight than to keep it off.
After the initial shock, your body recovers and does what it can to bring you back to your set point. It has some pretty good ways of doing that. As you start to drop weight and are further from your set point, you release more leptin.
Your brain maintains a leptin set-point to regulate how much fat you have in your body. As you gain more fat, the leptin level in your blood increases. When your leptin goes above your set-point, your body will take steps to bring it down. When you lose fat, the leptin level in your blood goes down. When it goes below your set-point, your brain will take steps to bring it up just like the thermostat in your house does trying to control the temperature on a cold winter day.
The higher leptin level increases hunger and cravings for carbs so you eat more. You may also become less active during the day. This can be subtle. If you’re a fidgeter, your brain may send the signal to stop tapping your foot or shaking your leg. You may not notice it, but you’re burning fewer calories throughout the day. It’s the body’s way of bringing you back to your pre-determined set point.
If your body is so focused on bringing you back to your set point, does it mean you can never sustain long-term weight loss? Not necessarily. One thing you can do is exercise. Higher intensity exercise is more effective than just walking. Resistance training is particularly beneficial since it boosts lean body mass, which burns more calories. Whether or not building lean body mass actually lowers a person’s set point is still unknown, although it does help with long-term weight maintenance. There is some evidence that regular aerobic exercise reduces a person’s set point.
The Bottom Line?
Set-point theory is one possible explanation as to why staying slim after losing weight is so difficult. You can’t easily change your genetically-determined set point but aerobic exercise and regular resistance training can help you avoid regaining the weight you worked so hard to lose.
International Journal of Obesity (2007) 31, 204-212.
Int J Obes (Lond). 2007 Feb;31(2):204-12.