Which should come first — the diet or the workout? When it comes to weight loss, some dieters are torn between the two. Supposedly, exercise makes you hungrier and leads to “reward” eating, so you should only diet.

Wrong, say researchers from Harvard University. According to a new study, diet and exercise go hand-in-hand. Turns out, pumping iron at the gym not only tones your muscles, but your brain, too, by changing the way it functions. Working out strengthens one of the most important muscles in maintaining fitness: inhibition. The more you sweat, the easier it is to resist another slice of cake. Exercise also aids your ability to sense fullness and know when to stop.

Need some more tools to bolster your willpower? It’s all about building healthy habits. Know what it takes to burn off the calories in a cheeseburger instead of a grilled chicken salad … and you’ll think twice before ordering. Develop a taste for lean, wholesome foods and soon you won’t miss your old fatty favorites. Imagine that every healthy choice you make brings you one step closer to your goal.

Second, slow down at the dinner table. Research shows that the slower we eat, the less calories we take in. It takes the brain 15 minutes to sense fullness, but we’re usually finished eating a meal or two by then.

As far as exercise, research shows the best tactic is to “just do it.” In the running community, it’s said that the hardest step is the one out the door. The same is true for exercise in general; don’t give yourself the chance to talk yourself out of going and just get to it. A study published in the Psychology of Sport and Exercise found that fit people make daily gym sessions nonnegotiable.

So hit the gym to flex your muscles and your willpower. Start a vicious cycle of healthy eating and exercising and you’ll be well on your way to your happy weight.