The most visible sign of obesity is excess body fat, usually measured by BMI. A BMI of 30 or more indicates obesity, while a person with a BMI between 25 and 30 is considered overweight. You can calculate your BMI using Healthdirect’s calculator for adults. However standard BMI calculations can inaccurately measure a healthy weight for people under 18 years of age, pregnant women, and people from certain ethnic backgrounds. If you’re usure, ask your doctor or dietitian if BMI applies to you.