People use the Body Mass Index (BMI) to assess the level of risk because of their weight. A BMI of between 20 and 25 is normal, 25 to 30 is overweight and over 30 is obese. Any score above 40 means a high risk of life-threatening diseases. Put the other way round, any loss of weight reduces the risk of dangerous diseases. Losing just 10% of your current weight significantly reduces the risk of diabetes, high blood pressure and heart disease. The longer you can maintain this loss, the better your chances of a long life.