In overweight adults, aerobic exercise training does not significantly alter total daily energy expenditure beyond the energy cost of the exercise itself, with metabolic adaptation occurring primarily through reductions in resting metabolic rate rather than reductions in non-exercise physical activity.

When overweight adults do regular aerobic exercise, their liver and kidneys shrink slightly because their cells become more tightly packed and lose some metabolically active tissue. This means these organs burn fewer calories at rest. At the same time, their muscles become more efficient at moving, so walking and other daily movements use less energy. Together, these changes cancel out the extra calories burned during exercise, keeping total daily energy use unchanged.