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Q: How is body fat measured and how is the term “obesity” defined by the medical community?

Dr. Rekha Kumar
Dr. Rekha Kumar

A: I’m a general endocrinologist, a specialist in diagnosing and treating health conditions related to problems with the body’s hormones. I focus on obesity medicine, which is its own field of medicine now. It’s growing fast, and there is now a fellowship (specialized training) in this subspecialty. If someone has concerns about their weight, they can talk to a specialist about their concerns.

It’s important to discuss how we define and measure obesity in the medical field because it is complicated. Body composition is the percentage of fat, bone, and muscle in your body. The most accurate ways to measure body composition are complex, such as submerging someone in water and measuring how much water is pushed out of the way. We can use air rather than water to measure body composition in a process called air displacement plethysmography (ADP). We can measure human body composition with dual-energy x-ray absorptiometry (DXA scan) — commonly used to measure bone density. However, water displacement, ADP and DXA scans take a lot of time; we can’t do them in the office, and they’re not covered by insurance.

Healthcare providers most often use BMI or body mass index, which is a calculation that uses weight and height. You may have seen these charts. You may have also been told that you have a high BMI that indicates obesity. That’s not always true. There are people with high BMIs that are healthy and people with lower BMIs that are unhealthy. We define the term “obesity” as an increase in body fat that impairs health.

Fat mass, body composition and family history can all affect your health. So, I would like to look beyond body mass index. Because measuring obesity and fat mass is complicated in practical terms, we can instead measure the extent of obesity (called “staging”) the way we do other medical conditions. To do so, we ask: Are they experiencing complications related to high BMI?

We can assess somebody’s obesity by looking at existing medical and mental health issues, as well as their ability to perform daily activities. This method is called the Edmonton Obesity Staging System:

Stage 0: There are no medical, mental or functional health problems related to a high BMI.

Stage 1: Patients have mild health complications of high BMI, such as prediabetes, slightly high blood pressure, mild psychological distress about one’s weight or mild functional impairments, such as joint pain.

Stage 2: Patients have health complications related to high BMI, such as diabetes, high blood pressure, osteoarthritis, or back pain.

Stage 3:   Patients have organ damage due to health complications related to high BMI, such as kidney damage from diabetes and diabetic neuropathy. We may also see mental depression or the need for joint replacements.

Stage 4:   This is the end stage of the disease. Patients need to use wheelchairs, potentially have congestive heart failure or require dialysis due to complications of obesity and diabetes.

If you have any concerns about your weight and how it may be affecting your spine conditions, contact us. We are happy to help you find the best solutions available.

  • Rekha Kumar, endocrinologist and weight management specialist at Weill Cornell Medicine

This question was answered during the episode of Spine Time called “Is Your Weight Hurting Your Back? How Your Daily Habits Affect Your Spine.” A recording of this webinar held on October 14, 2020, is available on YouTube. To sign up for future episodes of Spine Time, where you can ask questions of our spine specialists, subscribe here.

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