Diet or Exercise: The Final Verdict on Which Is Better for Weight Loss

Here's what science and dietitians think about the debate between diet and exercise—and which should be your biggest priority for weight loss. You’ve heard it over and over again: Diet and exercise are the keys to a healthy weight. As it turns out, though, one is far more important than the other. If you want to drop pounds, focusing on food is your best bet. (Here are the tiny diet changes that can help you lose weight.)

Diet is more important for weight loss

Despite the constant message to burn fat and calories away at the gym, people who only change their diets lose more weight than those who only increase physical activity, according to a report in the journal Systematic Reviews. In fact, another study in the journal PeerJ found that over three years, people who got 30 minutes or more of physical activity a day actually had higher rates of weight gain than those who exercised less. So why isn’t gym time the miracle weight-loss machine we’ve been led to believe?

Basically, it’s way easier to avoid calories in the first place than to try to burn them off, says registered dietitian nutritionist Marjorie Nolan Cohn, MS, RDN, spokesperson for the Academy of Nutrition and Dietetics. Working off a 100-calorie cookie is one thing, but it would take hours at the gym to negate 1,200 calories from a burger and fries. “You can’t exercise off a weekend of terrible eating,” says Nolan Cohn. Committing to a 30-minute workout program? Easy enough. Turning your entire eating plan on its head? Not so much. (Here are the sneaky things that are making you gain weight.)

You can’t out-exercise a poor diet If you don’t pay attention to portion sizes, you might eat more after you start a new workout routine, says Nolan Cohn. Not only will your appetite increase naturally from the energy burn, but you might also slack off on healthy food choices. “There’s this idea that you’ve earned it to eat something because you worked out,” says Nolan Cohn. “It winds up holding people back.” Half an hour on the treadmill might blast away 300 calories, but just one slice of cake could totally negate that hard work—and then some. This energy to calorie ratio is partly why you can flatten your belly without doing a single crunch.

You might have heard that muscle weighs more than fat. That’s true, but it doesn’t mean you should claim the bigger number on the scale is all muscle. “That’s a few pounds, not 20 or 30 pounds,” says Nolan Cohn. “It’s not an excuse for the weight gain.” If you’ve been exercising without results, your diet is probably to blame.

The most benefits come from both diet and exercise Still, don’t cancel your gym membership. A systematic review of studies found that pairing diet with exercise was even more successful for weight-loss than diet or exercise alone. Research shows focusing on both led to better long-term results, or sticking healthy habits, which explains why people who double up are more likely to maintain weight loss after one year. And another study found that almost 40 per cent of people who managed their weight loss after four years were still doing 150 minutes of exercise per week.

Plus, exercise doesn’t just burn calories and build muscles—it boosts endorphins too, says Nolan Cohn. “It improves feelings of positivity or accomplishment,” she says. “When you combine those forces [of diet and exercise], it reinforces losing the weight and keeping it off.” Weight maintenance is just the beginning when it comes to reasons to exercise. Studies have linked physical activity to all kinds of other health benefits, from heart health and immune system function to mental health and sleep improvements. “The list just never ends,” says Nolan Cohn. So if you only want to do one, chancing your diet is more valuable. To live your healthiest life, however, you’ll want a combination of both diet and exercise.