Energy balance

The modest weight loss observed from aerobic exercise interventions is primarily caused by low prescribed exercise energy doses combined with a compensatory increase in caloric intake, rather than metabolic adaptation or reduced non-exercise activity.

If you are exercising to lose weight but not seeing results, do not assume your metabolism has slowed down. The most likely culprits are that your exercise dose is too low to create a significant deficit, or you are unconsciously eating more to compensate for the activity. To lose weight, you must either increase the intensity/duration of exercise significantly or, more effectively, manage your caloric intake to ensure it does not rise to match your increased expenditure.