Fat
Fat is a major energy source for the body during long endurance outings. The primary location for fat storage is adipose tissue (i.e., body fat) within the body. The majority of the adipose tissue that is used for energy is called subcutaneous fat (below the skin). Adipose tissue is comprised of adipocytes, or fat cells. Adipocytes are where triglycerides are stored and synthesized. Fat, along with carbohydrates and protein are known as macro-nutrients.