Metabolism is driven by many body systems--thyroid, pituitary, brain etc.. We generally have no control over it. We can, however, affect it by not eating, sleeping or being in poor health. Diseases obviously can overtake it as well. Diet is important and can influence your metabolism. An example is eating high glycemic foods eg white potatoes, breads etc which drive up triglycerides from the liver that have a negative effect on your arteries.