People come in all shapes and sizes. How can you tell if you are obese? Your bathroom scale alone can't tell you. According to the National Institutes of Health, the most accurate indicator of obesity is the Body Mass Index, or BMI.

Your BMI is a ratio of your weight and your height, and it's how most physicians determine obesity.

In general, this ratio should be between 20 and 26 (although people who are over 35 may be fine at a slightly higher number). If your BMI falls between 20 and 26, your height and weight are proportional, which is good.

Physicians consider people who are above the recommended BMI range for their age to be "obese." For example, someone who weighs 160 pounds and is 5' tall has a BMI of 31, which is considered obese. Someone who weighs 160 pounds and is 5'11" tall has a BMI of 22, which is within the optimal range.