You might always be destined to weigh 10 to 15 pounds more than you’d like. Neuroscientist Sandra Aamodt says that the brain has a tight control over weight regulation. When you drop below your brain’s target weight, it fights to bring you back to equilibrium. No matter how hard you fight to shed the extra pounds, your brain is working just as hard to get you back to your “set point” weight.

The Brain Is a Weight Thermostat

According to Aamodt, the hypothalamus gland regulates hunger. Chemical messengers activate the metabolism when conditions in the body change. When your weight drops too low, it kicks into action to motivate you to eat more.

The brain is incredibly efficient at regulating weight. Early in evolution, food was scarce. The brain was hard at work controlling metabolism to squeeze the most energy possible out of every nutrient. When you try to voluntarily deprive yourself of food, the same mechanisms kick into effect.

Set Point Theory

Aamodt coined this principle as the set point theory: Your brain is convinced that your body as an ideal weight, or “set point” for survival. Any large deviation sets off the alert system. You should never fall 15 pounds below your set point. When you do, your brain screams at you to eat.

If you try to put on weight, don’t pack on more than 15 extra pounds. Those first 15 are easy to come by until you hit your set point. Your body’s metabolism will start to kick into high gear in an attempt to shed the unnecessary weight. Your primal brain wants you lean and mean so that you can run from predators and hunt for food.

Eat Well and Set Healthy Goals

Is your goal to be as healthy as you can be or to live up to an ideal body image? Chasing a skinny body image may be setting yourself up for failure.

Optimize your exercise and eating habits so that you’re taking in clean fuel and working out to reduce stress. Let how you feel be your guide, not how you look. If you’ve always been a little on the heavy side, it could be that your brain doesn’t want you to be rail-thin.