You’re ready to start living a more healthy lifestyle and excited about the change. If you’re like most people, you might sign up for the gym and buy new sneakers even before you consider going through your cabinets and getting rid of food that is high in sugar, ultra-processed or otherwise unhealthy.

There’s something about exercising that immediately brings to mind physical fitness, which for many people is closely connected to weight loss. And yet, experts say that focusing on exercise is not the fastest way to drop pounds. In fact, when it comes to losing weight, your diet is much more important than your exercise routine. Here’s why:

Weight Loss 101

In order to lose weight, you need to create a calorie deficit, meaning that your body is burning more calories each day than it is taking in. In order to lose a pound, you need to burn 3,500 more calories than you take in, according to the Mayo Clinic. If you want to lose a pound a week, that means running a deficit of about 500 calories each day.

Why exercise isn’t that effective at helping your lose weight.

You may see that 500 calorie number and think, “Easy!” After all, about an hour of moderate exercise, like a brisk walk or slow jog, can burn that amount, according to the National Institutes of Health. However, it’s not quite that simple.

For starters, experts say that very few people stick to a routine of exercising every day, especially for an hour. In addition, this study found that more exercise isn’t associated with greater weight loss (in part because all that exercise makes you hungry, so you might be eating many of the calories you burn in the gym).

On the days that people do exercise, they often unconsciously do less physical activity to compensate for the exertion, research has found. They spent less time doing household chores, walking, and shopping. Though they typically burned more calories on the days they exercised, the total was half of what would be expected because of the decrease in other activities.

Finally, the exercise you do in the gym only accounts for 10 to 30 percent of the calories that your body burns each day, Alexxai Kravitz a neuroscientist and obesity researcher at the National Institutes of Health, told Vox. The rest of the calories are burned by essential functions like breathing and digestion, which you have no control over.

Why focusing on food is more efficient.

Although we have relatively little control over the amount of calories our bodies burn in a day, we have total control over how many calories we take in, since the only source of calories are the foods and drinks that we consume. Because of this, it’s easier for many people to focus on reducing calories they consume rather than focusing on burning more calories.

Americans get up to 60 percent of their caloric intake from ultra-processed foods, which are usually high in sugar. Eliminating these foods can easily help you create a calorie deficit that leads to weight loss. In fact, the connection between limiting sugar consumption and weight loss is so strong that this study in the British Medical Journal concluded “intake of free sugars or sugar sweetened beverages is a determinant of body weight.”

Of course, exercise has wonderful benefits for physical and mental health, including lowering the risk for type-2 diabetes, stroke, heart disease, and dementia. But if you’re determined to see the needle on the scale move, it’s best to focus on quality nutrition in order to lose weight.