Body fat refers to the excess fat stored in a person's body, particularly around their abdomen, hips and thighs. It is an essential energy reserve that helps the body function properly during periods of fasting or starvation. However, when there is too much body fat it can lead to health problems such as obesity, heart disease, diabetes, high blood pressure, and certain types of cancer. Body fat percentage is often used as a measure of fitness and health, with an optimal range varying depending on age, sex, and other factors.