The set point theory is the idea that the body has a preprogrammed weight that it likes to be at to function efficiently. And there is scientific evidence that suggests there is some truth to this; the body uses a variety of metabolic and hormonal mechanisms—like slowing down metabolism when you cut your calorie intake, for instance—to maintain its weight when you try to slim down.

So does this mean that trying to lose weight below your “set point” is futile, since your body will try to fight it and always win? No, weight management is more complicated than that. Many parameters control weight, including genetics, but so do external factors, like stress and your eating behaviors. Plenty of people slim down and settle at a lower weight permanently—but you should follow a safe, gradual weightloss plan so that your body can adapt over time. (Plus, you’ll be more likely to keep the pounds off in the long term if you take on sustainable healthy eating habits.) Crash dieting (like restricting your calories too intensely) can cause your body to try to hold on to fat so it stays at its happy weight—don’t try it.

Health’s medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.