Not long ago, the secret to losing weight seemed straightforward: Just give up bread. Not long before that, it was all about avoiding fat. And when those theories sprung leaks, a long list of diet fads was there to fill the holes — cabbage soup, grapefruit, eating for your blood type … the list goes on and on.

To help you stop diet-hopping, we’ve peeled away the layers of hype to reveal the core concepts and surprising science behind what really works for weight loss. Follow these nine laws for hitting that perfect number on the scale — and stay lean for life.

The laws of lasting weight loss