Problems With BMI
Body mass index doesn't tell the whole story about your body, though.
For example, your BMI doesn't show whether your weight is fat or muscle. If you're a super-fit athlete, your muscle might put you in the "overweight" or "obese" range. Or, if you're elderly and have lost muscle mass over the years, your BMI could be normal, but you're not in as good shape as you think.
The formula also doesn't show where your fat is located on your body. And it doesn't consider differences among ethnic groups.
The CDC recommends that doctors use BMI a first step to screen adults for weight problems. Your doctor should also consider other things, like how fit you are.
Check Your Waist Size
Get a tape measure and wrap it around your belly.
If your waist is more than 35 inches around and you're a woman, or if it's more than 40 inches and you're a man, you might have too much belly fat.
Research shows that carrying extra fat around your stomach is unhealthy, no matter what your BMI is.
The Edmonton Scale
Obesity experts also use the Edmonton obesity staging system. It takes BMI a step further by relating it to your health. There are five stages:
Stage 0: You don't have any health problems related to your weight.
Stage 1: Any weight-related health problems are mild (such as borderline high blood pressure or occasional aches and pains).
Stage 2: You have an obesity-related chronic disease, such as high blood pressure, type 2 diabetes, sleep apnea, or osteoarthritis, and you have moderate problems doing daily activities or feeling well.
Stage 4: This is the most severe level of weight-related chronic health conditions, which are extreme and life-threatening.
If your doctor doesn't use this system, ask her to tell you how your weight is affecting your health.
What Obesity Does to Your Body
"When people become obese we start to see disease rates go way up," Wang says.