Body fat refers to the weight of fat in the human body and is generally expressed as body fat percentage (F%), which is the percentage of the weight of fat in the human body to the total body weight and is an important measure of whether a person is obese. It is usually considered that the body fat percentage of normal adults is 12%-23% for men and 16%-27% for women, respectively. The body fat percentage for athletes can vary with the sport, generally 7%-15% for male athletes and 12%-25% for female athletes. High body fat percentage, weight more than 20% of the normal value is considered obese, body weight growth can significantly increase the probability of knee discomfort, osteoarthritis, hypertension, diabetes and other diseases, at this time need to reduce calorie intake, eat less high-calorie food such as fried chicken, barbecue, etc., and combined with jogging, swimming and other forms of exercise to reduce weight. If the body fat percentage is too low and reaches the safe lower limit of body fat content, i.e. below 5% for men and below 15% for women, it can cause functional disorders such as amenorrhea and slowed reaction time, etc. At this time, you can increase the intake of high quality protein, fat and other nutritional elements to achieve balanced nutrition.