The higher the BMI, the greater the risk of some diseases, including high blood pressure, coronary artery disease, stroke, osteoarthritis, some cancers, and type 2 diabetes.BMI Numbers - what do they mean?For adults older than 20 years:A BMI below 18.5 is considered underweight.A BMI between 18.5 and 24.9 is considered a healthy weight.A BMI between 25 and 29.9 is considered overweight.A BMI of 30