As the endocrine system controls the rate and direction of metabolism, what you consume and your level of physical activity will overall influence the speed of your metabolism and how much you weight you gain. The belief that your metabolism is to blame for increased fat is not correct. Eating more calories than you can burn is the primary cause. The best way to control how many calories you burn is through your level of physical activity, according to the Mayo Clinic. What appears to be a faster metabolism in others is more often a more active lifestyle, that leads to weight loss or maintaining a steady weight.