To lose body fat, you must consume fewer calories than you expend, and the size of this calorie deficit has a greater impact on fat loss than whether you do running, weightlifting, or other forms of exercise.

All the women lost weight by eating fewer calories and exercising, but those who cut calories slowly had better health results than those who cut a lot quickly. This suggests that how big the calorie deficit is matters more than what kind of exercise you do.

When people burn more calories than they eat, they lose fat—no matter what diet they follow or where they are. This study showed that even in a tough environment like high altitude, people lost the same amount of fat just because they ate less, not because of what they ate.

You can't choose where you lose fat by doing specific exercises—like crunches for belly fat. The only way to lose fat is to burn more calories than you eat, and your body decides where to take fat from, not your workout.

When people lose weight by eating less, their body sometimes loses muscle too — but this study found that blocking certain signals can help keep the muscle while making fat loss even better. This still means eating fewer calories is the main reason for losing fat.

Even though some people don’t lose weight as expected when eating less and moving more, it’s still because they’re not burning more calories than they eat — it’s just that their bodies react differently. The study says cutting calories is still the main way to lose fat, no matter what kind of exercise you do.