Body mass index (BMI) is a guide to help people estimate their total body fat as a proportion of their total body weight. BMI can indicate risk for developing certain medical conditions including diabetes, high blood pressure, and other metabolic conditions. BMI is less accurate for assessing healthy weight in some groups of people – find out if BMI applies to you. Waist circumference is a good indicator of 'hidden fat' around organs in our bellies. It may be a better guide than BMI alone in estimating risk for the same types of medical conditions.