For women who aren't very overweight, adding aerobic exercise to a calorie-restricted diet doesn't help them lose more fat than just eating less — as long as both groups burn the same total calories over 8 weeks.

What we've found so far is that adding aerobic exercise to a calorie-restricted diet does not lead to greater fat loss in non- or moderately obese women when the total energy deficit is matched over 8 weeks [1]. The evidence we’ve reviewed leans toward the conclusion that fat loss is similar whether the calorie deficit comes from diet alone or from a combination of diet and aerobic exercise, as long as total energy expenditure is the same [1]. Our analysis of the available research shows that for women who are not severely overweight, the method used to create the calorie deficit—whether through eating less or through exercise plus eating less—does not change the amount of fat lost, provided the total deficit is equal [1]. This suggests that the body responds to the overall energy gap, not how it’s created [1]. We looked at 46 supporting assertions and found no studies that contradicted this finding [1]. However, we want to be clear: this conclusion is based on what we’ve reviewed so far, and our understanding may evolve as more evidence becomes available. We are not saying aerobic exercise has no benefits—only that, in terms of fat loss under matched energy deficits, it doesn’t appear to add extra fat loss beyond what diet alone achieves in this group. The practical takeaway: If you're a woman with mild or moderate excess weight and your main goal is fat loss, focusing on creating a consistent calorie deficit—whether through food, exercise, or both—matters most. Adding cardio may improve fitness or help with adherence, but it won’t necessarily make you lose more fat if your total calorie burn stays the same.