Body mass index (BMI) is a ratio often used to diagnose and measure obesity. However, obesity is a complex condition that affects many aspects of your health, and it can’t always be accurately assessed with BMI. Effective screening goes beyond weight alone and considers body composition, underlying health conditions, waist circumference, family health history, and other health markers.

So, how do healthcare providers get a complete picture of your health? What’s the best way to screen for obesity? The answer often involves a combination of tests. This article explores the key screening methods and how they give healthcare providers insight into your unique condition.

BMI Isn’t Always Best

BMI is a go-to measure for obesity for its quick, simple approach. The BMI calculator determines a score based on your weight and height. If your BMI score is over 30, you will be diagnosed with obesity. You may fall into one of three obesity classes based on your BMI score:

• Class 1 obesity — A BMI between 30 and 34.9
• Class 2 obesity — A BMI between 35 and 39.9
• Class 3 obesity — A BMI of 40 or higher

While BMI is a helpful measurement, it doesn’t account for several aspects of health. For one, it doesn’t differentiate between fat, muscle, bone, and other body tissue. That means a person with a lot of muscle and little body fat can have a BMI in the overweight or obese range.

It also doesn’t consider a person’s sex, race, ethnicity, age, or health history, which can affect how a person carries weight on their body and what a healthy level of body fat should be. Having a BMI score in the obese range doesn’t automatically mean a person has other health conditions, just as having a BMI score in the normal or underweight range doesn’t mean a person is totally well. In other words, BMI doesn’t capture the full picture of how healthy or unhealthy you are.

What’s the Best Assessment for Obesity?

Weight isn’t a direct indicator of your health. When screening for obesity, talk to your healthcare provider about additional testing methods. There’s no single “best” test. A combination of measurements will provide the most complete and accurate health assessment.

Here are some other tests your healthcare team may order.

Waist Circumference

Where you carry weight on the body matters. Visceral fat, located in the waist and abdomen, can wrap around vital organs like the pancreas and liver. Excess fat in these areas can put you at an increased risk of heart disease and type 2 diabetes. That’s why some providers use waist circumference (WC) as a key health indicator. A waist size larger than 40 inches for men and 35 inches for women may suggest a risk for obesity-related health issues. WC is measured around the waist right above the top of the hipbones, checking the measurement after breathing out.

Waist-Height Ratio

Waist-height ratio is another way to measure abdominal fat by dividing your WC by height. Experts recommend “keeping your WC to less than half your height.” A waist-height ratio greater than 0.5 may point to increased health risks. In fact, research shows that waist-height ratio is a more accurate indicator than BMI for assessing your risk for heart problems and metabolic syndrome, which includes health conditions such as type 2 diabetes and high blood pressure.

Bioelectrical Impedance Analysis

One of BMI’s disadvantages is its inability to distinguish body composition. Bioelectrical impedance analysis offers a simple, noninvasive way to estimate your body’s fat, muscle, and water content. It works by sending a small electrical current through your body. Because fat, muscle, and water conduct electricity differently, the test can estimate your body composition based on how the current flows.

Muscle tissue and water conduct electricity well, so the current passes through them quickly. Fat, on the other hand, resists the current and slows it down. This resistance helps your provider tell how much fat is in your body versus lean mass.

Bioelectrical impedance analysis may not be an accurate predictor of health in individuals with severe obesity. Accuracy can also vary based on body size, gender, age, and ethnicity.

Digital Anthropometry

Anthropometry refers to the study of human body measurements. Thanks to recent technologies, you may no longer need to reach for your measuring tape. Digital anthropometry can quickly and accurately capture several body dimensions at once using a 3D body scanner. The scanner produces a full-body image that maps your proportions and shows fat distribution.

Digital anthropometry can be less time-consuming and less expensive than other imaging methods. It also can be a precise screening tool for people with obesity.

Dual-Energy X-Ray Absorptiometry

Dual-energy X-ray absorptiometry is a quick, painless scan that can reveal a lot about your body composition. It provides an in-depth analysis by categorizing your body weight into fat tissue, bone density, and lean mass. Research shows it may be a more effective obesity measure than other methods. It can also help you track changes in your body over time.

Blood Tests

Obesity raises your risk for several underlying health problems, including:

• Cardiovascular (heart) disease
• Hypertension (high blood pressure)
• High cholesterol
• Type 2 diabetes

Blood tests uncover what’s going on beneath the surface. They can provide a clearer picture of your health and explain weight gain to guide treatment decisions. Your doctor may order blood tests to check:

• Cholesterol levels to assess heart disease risk
• Glucose and A1c levels to screen for prediabetes or diabetes
• Thyroid function to detect hypothyroidism
• Liver function to check for signs of metabolic-dysfunction associated steatotic liver disease (MASLD)

Talk to Your Doctor About Obesity Screening

Obesity doesn’t come in a single size or shape. That’s why screening should go beyond just weight or BMI. Talk to your provider about your obesity screening options. They can recommend the best tests to give you a more complete picture of your well-being, including both physical and mental health.

When discussing obesity screening with your healthcare provider, consider asking:

• What tests can assess my health beyond BMI?
• How do my results impact my life expectancy or risk of other medical conditions?
• Are there any medical factors, such as family history or other health issues, that could be contributing to my weight?
• What steps can I take based on my screening results?

Obesity affects everyone differently. Understanding your overall health can identify the risk factors that impact your quality of life. Your clinician will use your test results to create an obesity treatment plan for your unique needs, as well as determine a healthy weight to set as a goal. Depending on how obesity is impacting your health, your plan may include:

• Lifestyle changes, including physical activity and a balanced diet
• Medications
• Bariatric surgery
• Other weight loss or weight management methods

Find Your Team

MyObesityTeam is the social network and online support group for people with obesity and their loved ones. More than 56,000 members come together to share experiences, seek advice, and offer support.

Which screening methods have you tried for assessing obesity? What have you learned about your health from these tests? How did your results guide your treatment approach? Leave a comment below, or start a conversation by posting on your Activities page.