It's the time of year for motivational stories. A "new year, new you" narrative, one that's often accompanied by inspiring videos from the gym of a person's dramatic weight loss progress. And if those transformational tales have moved you to make some changes in your own body, here are a few things you should understand: Weight is only one imperfect metric of health, attractiveness and happiness. There are a multitude of compelling physical and mental health reasons to exercise that have nothing to do with your size. And finally, as a 2017 report in Diabetes Spectrum notes, "Most, but not all, study data indicate that exercise alone plays a very small role in weight loss." Or as a colleague observed to me recently, "You don't lose weight in the gym; you lose it in the kitchen."
It's simple math — and so much more. To lose one pound, you need to shed 3,500 calories. Now let's say on a typical morning I run three miles, an aerobic exercise that burns more calories than stretching or strength training. That's about 300 to 350 calories. That's it. Then I'm going to go eat breakfast. "The old saying that you can't outrun a bad diet is annoying to hear, but it's true," says Dan Gallagher, a registered dietitian with Aegle Nutrition.
"Most people are exercising for maybe half an hour, which only burns a small fraction of the calories you consume each day," notes Gallagher. "You have to pay attention to your caloric intake if you want to lose weight and build muscle, unless you'd like to run 10-plus miles every day to work off what you choose to put in your mouth."
Another reason exercise alone won't work for weight loss is our human capacity to adapt. "Our bodies will eventually reach a plateau with exercise where they will not burn more calories," explains Lauren Thayer, a registered nurse at Health Canal. "Some research even says that working out does very little for weight loss. The body's metabolic adjusts constantly and those who perform high intensity workouts daily and those who are sedentary have a very similar daily energy expenditure." A 2016 study out of the journal Cell Biology backs this up, noting, "People who did more than moderate activity had nothing to show for it in terms of increasing the amount of energy they expended." That's where food comes in.
"While gym videos flood our feeds in January, there's a tendency to overlook the importance of diet in the weight loss equation," says Andrew White, a certified personal trainer and co-founder of Garage Gym Pro. It's not just about overvaluing exercise; it's about not always being realistic about food. "Many people believe they're eating less than they actually are," says White. "Portion control and understanding calorie content are vital. A food diary or app can be incredibly eye-opening in this regard."
Similarly, unless you're Michael Phelps in his prime, you can't treat an exercise plan as a hall pass to eat more. "After a good workout, there's a temptation to reward ourselves with high-calorie foods, which can counteract our efforts in the gym," says Andrew White. "It's easy to overestimate the number of calories burned during a workout and compensate by eating more. This can negate the calorie deficit needed for weight loss. The cornerstone of weight loss is consistently consuming fewer calories than your body burns. This doesn't mean starving yourself but rather making smarter, healthier food choices."
Or you may find yourself getting hungrier, especially if you're going hard on a new workout and strict diet plan. "It is 2-fold," explains Kimberly Gomer, a Miami dietician and nutritionist. "One is the increase in hunger that some people get from exercise (and accentuated if they are also restricting calories). Another issue is that when the body is challenged through exercise, to maintain homeostasis, the body will increase hunger hormonally by sending out hunger cues like ghrelin. Studies have shown that it is very easy to 'out eat' your workout."
In my own life, doing yoga and training for races have over the years have undeniably affected how my body looks and performs, but even intense, regular exercise has rarely affected the numbers on a scale. Things that have made me lose weight? Cancer, COVID and depression, and I can recommend none of them. Just as exercise alone isn't a magic bullet for healthy weight loss, neither is just eating less — as anyone who's been sick, stressed or on a stupid diet can attest. But it does matter. "Exercise is important for health heart and muscle growth," explains which in turn helps weight loss by creating more metabolically active tissue that burns fuel, instead of storing it as fat," explains Brittany Placencia, a nutritionist and the founder of Simple Plate Nutrition.
Beyond that, while it might not make for as compelling content as a clip of someone lifting victoriously at the gym, building consistent habits and consuming appropriate portions of nutritious food are the way to go. "Having enough protein, healthy fats, and fiber at each meal and snack is the key to satiety and balanced blood sugar levels, the weight loss trifecta," says Placencia. "For example, instead of snacking on an apple alone, which seems like the healthy thing to do, pairing it with peanut butter gives the snack healthy fats and protein along with the fiber from the apple. This will keep you satisfied for longer than the apple alone and will allow your blood sugar level to have a lower spike. Paring the right foods (protein, healthy fat, fiber) will help decrease a spike in blood sugar, allowing more time for your body to burn fuel, not store it."
I'm not suggesting that you need to lose weight, or that just being smaller is a realistic or healthy goal for anybody. What I am saying is that if for whatever reason you have decided you want to lose weight, you're going to need to take in fewer calories, and choose them wisely. "Long-term success comes from integrating balanced eating habits and regular physical activity into your lifestyle," says Paula Sierzega, a triathlon athlete and blogger. "To really make a lasting change, it's about finding that harmony between what you eat and how you move. After all, your body deserves a lifestyle it can sustain and thrive in."
