How are overweight and obesity diagnosed?

The most common way to find out whether you're overweight or obese is to figure out your body mass index (BMI). BMI is an estimate of body fat and a good gauge of your risk for diseases that occur with more body fat. The higher your BMI, the higher your risk of disease. BMI is calculated from your height and weight.
Although BMI can be used for most men and women, it does have some limits:
It may overestimate body fat in athletes and others who have a muscular build. It may underestimate body fat in older persons and others who have lost muscle.
Body Mass Index for Children and Teens
Overweight is defined differently for children and teens than it is for adults. Because children are still growing and boys and girls mature at different rates, BMIs for children and teens compare their heights and weights against growth charts that take age and sex into account. This is called BMI-for-age percentile. A child or teen's BMI-for-age percentile shows how his or her BMI compares with other boys and girls of the same age.
Waist Circumference
Health care professionals also may take your waist measurement. If you have abdominal obesity and most of your fat is around your waist rather than at your hips, you're at higher risk for heart disease and type 2 diabetes.
Specialists Involved
A primary care doctor will assess your BMI, waist measurement, and overall health risk.If you are, you and your doctor should work together to create a treatment plan. The plan should include weight loss goals and treatment options that are realistic for you.
Your doctor may send you to other health care specialists if you need expert care. These specialists may include:
An endocrinologist if you need to be treated for type 2 diabetes or a hormone problem such as an underactive thyroid. A registered dietitian or nutritionist An exercise physiologist to figure out your level of fitness and show you how to start physical activities suitable for you. A bariatric surgeon if weight loss surgery is an option for you. A psychiatrist, psychologist, or clinical social worker to help treat depression or stress. This answer is based on source information from the National Heart, Lung and Blood Institute.
Marisa Moore
Nutrition & Dietetics

The most widely accepted method to determine overweight and obesity is Body Mass Index (commonly referred to as BMI). Your BMI is calculated based on your height and weight. You can quickly find out your BMI using either of the online calculators available.

  • A normal BMI spans 18.5-24.9. This is considered a healthy, target weight range.
  • A BMI lower than 18.5 is considered underweight.
  • A BMI of 25-29.9 is considered overweight and a BMI greater than 30 is considered obese.

While BMI is the most widely used method to determine overweight and obesity status, it’s important to note that it is not the best assessment tool for all people. For example, older adults with less muscle mass and body builders who are very muscular are two groups for which BMI may not be as useful. Other measures such as waist circumference, waist to hip ratio or percent body fat may be used.

In any case, it’s good to know your waist circumference which has been shown to predict risk for heart disease (or the likelihood that you’ll have a heart attack or stroke, for example). The goal for women is to achieve a waist circumference of less 35 inches or less; for men, less than 40 inches.

Have you ever heard someone somewhere compare a person to an apple or a pear? Interestingly, research has shown that the location that excess body fat accumulates makes a difference. People with a pear shape, those who carry excess fat in the hips and thighs, tend to be at a lower risk for heart disease compared to the apples who carry excess fat in the midsection (belly).

If all of these numbers make your head spin, no worries. I encourage you to find a registered dietitian in your area who can assess where you stand, where you need to go and how to get there. It’s easy to do. Just go to to find a registered dietitian in your area.

Jim White
Nutrition & Dietetics

The most common way to diagnose if a person is overweight or obese is by finding a person's Body Mass Index (BMI). BMI is calculated by using an individual’s height and weight. It is typically an accurate way to determine if a person is at risk for diseases that are related to being overweight. Your BMI can easily be found online. A normal BMI is between 18.5-24.9. A BMI of 25-29.9 is considered overweight and a BMI higher than 30 is considered obese. 

Sometimes BMI is not always accurate, especially when dealing with athletes, and this is when something like the BOD POD can be used to determine actual body fat percentage. 

Obesity, or just being overweight, requires a thorough blood workup and physical examination to determine the extent of risk factors that may be present. There are some patients that do everything right to try and lose weight, but no matter what they do they have a hard time. In these patients, thyroid or hormonal issues have to be ruled out. 

Continue Learning about Obesity

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.