If you’re like many resolution setters this time of year, you’ve already mapped out a route to your local gym. Maybe you’re planning to pound the treadmills or sweat it out in crowded studio classes. But if your ultimate goal is to drop extra pounds, you might want to ask how far all those miles and squats will really get you. According to a number of weight loss experts, focusing on your nutrition could give you a lot more bang for your buck. “By far, diet outweighs exercise if you want to lose weight,” says Heather Mangieri, RDN and spokesperson for the Academy of Nutrition and Dietetics. “You have to change your diet to change body composition. You can never out-exercise a bad diet.” So don’t sweat it—at least not quite so much. Here’s where to start with a weight loss resolution.

Research shows that exercise alone won’t help you lose weight, and contrary to popular opinion, it’s not the right message for the worldwide obesity epidemic. A recent study reveals why, suggesting that your body adjusts to higher activity levels, so while you may burn extra calories initially, eventually that rate will plateau. And there is some disheartening research, indicating that solely using exercise as a weight loss method can actually lead to weight gain. “Clients always say, ‘I’m doing all of this activity, but I just can’t lose the weight,’” confirms Mangieri. “I even have athletes who are training for 5Ks, 10Ks, and half marathons, and still gaining weight.”

When you crunch the numbers, it makes sense. The thing is, exercise makes you hungry, and it’s surprisingly easy to overcompensate with extra calories. People tend to overestimate how many calories they’ve burned during exercise—often by more than twice as much, and then feel like they deserve a treat. From a simple math perspective, 30 minutes of jogging can burn about 295 calories, cycling burns around 295 calories, and gentle yoga can torch about 90 calories. With one cheeseburger, donut, or beer, you’re making up the difference, and then some.  

The interesting thing is that many people are willing to spend a lot of time, money, and energy on expensive gym memberships and boutique fitness classes—and then say they’re too busy to cook. Even if you only spend 15 minutes driving to and from the gym every day, that’s 30 minutes that you could have put toward cooking a healthy dinner. And if you spend $30 a pop, 3 times per week on fancy circuit or spin classes, that’s $90 you could dedicate to your grocery budget. That wild salmon doesn’t sound quite so outrageous now, right?

Of course, there are so many more reasons to exercise, and physical activity is amazing for your overall health and wellness. It’s just that if you want to lose weight, it may not be the best or only answer. “Honestly, I think people just don’t know where to start,” says Mangieri. “It’s easy to say you’re going to go to the gym for an hour. It’s much harder to think about what you’re eating all day, every day.” She recommends setting goals that are just as specific and achievable for healthy eating, which could be as simple as drinking a big glass of water right when you wake up, getting protein at breakfast, filling half of your plate with colorful vegetables, or going for a walk in the evening, instead of eating ice cream on the couch.

“The first step is to change your mindset, and mentally decide that you are a healthy person,” Mangieri encourages. “But it’s never just one lifestyle change! Make sure every part of your life proves it. Eat nourishing foods and drink plenty of water. Get out and move and build strength. And don’t forget to sleep and de-stress. One good decision supports another.” But also, if you really don’t know where to start with a healthy diet for weight loss, talk to a registered dietitian. That could ultimately be money much better spent than on a personal trainer.