Energy balance

Aerobic fitness level (VO2 max) does not independently increase daily energy expenditure in weight-stable humans; its apparent association with higher energy expenditure is entirely mediated by its positive correlation with fat-free mass (FFM).

If you are weight-stable, your daily calorie expenditure is driven almost entirely by your fat-free mass (muscle and organ mass), not by your aerobic fitness level (VO2 max). While exercise improves fitness, it does not independently boost your resting or total energy expenditure beyond the metabolic cost of the activity itself and any muscle gained. To increase your baseline energy expenditure, focus on preserving or building fat-free mass rather than assuming high cardio fitness alone will significantly raise your daily burn.