The camera zooms into a torso to focus in on a blood vessel surrounded by muscle tissue and immature fat cells. After the body takes in food, the circulatory system delivers nutrients and energy to the body's cells. Immature fat cells expand and transform into mature fat cells when there is an excess of energy in the body (caused by overeating). This is the way that the body stores extra nutrients in case we need them later. If the body continually receives and stores extra nutrients, this can lead to a large amount of fat in the body. If overeating leads to obesity, many health risks such as heart disease, diabetes, high blood pressure, and cancer are increased.