In my late 30s, I was in the best shape of my life, cycling 20 to 30 miles daily, pumping iron regularly, and eating a plant-forward Mediterranean diet. Digestive issues I’d been dealing with had dissipated, and I was sleeping well after years of insomnia. I felt healthier than ever.
Imagine my surprise when my doctor told me I was overweight.
Many of us have faced this puzzling experience. Definitions of overweight and obesity often stem from misleading metrics such as the body mass index (BMI) my doctor used. These classifications can lead to a range of misunderstandings about what a higher body weight means for your health — not to mention the significant stress of being told you’re unhealthy solely because of your weight.
Given this confusion, some healthcare providers are turning to other metrics, including measurements of metabolic health, to determine whether a patient’s weight poses a health risk. They may deploy tests that measure stress hormones, glucose regulation, hormonal balance, thyroid and gut health, and inflammation, all of which affect how well your body converts food into energy and offer insight into your metabolic functioning.
The questions that follow examine why a metabolic framework for obesity might be a better starting point for determining the true status of your health.
Why do we gain weight?
While we typically assume weight gain is primarily about dietary choices — and they certainly can play a role — it can be influenced by a variety of factors. These include genetics, hormone dysregulation, sleep, stress, and certain medications.
Researchers are also investigating the role played by exposure to environmental toxins, sometimes called “obesogens.” These chemicals are often found in everyday items and include bisphenol A (BPA), which is employed in making plastics, and phthalates, endocrine disruptors commonly used in personal-care products. They can disrupt the body’s normal metabolic processes and endocrine function, promoting fat accumulation.
Excess weight can contribute to impaired cardiovascular function, joint stress, and breathing challenges, like sleep apnea. These physical impacts can be significant. Still, weight alone doesn’t provide a complete picture of a person’s overall metabolic health.
What’s wrong with relying on BMI as a measure of weight health?
Your body mass index is the measure of your weight in kilograms divided by the square of your height in meters. It’s widely used by healthcare providers to classify people as underweight, normal weight, overweight, or obese. (Learn more at “Beyond BMI: Why True Health Is About More Than What You Weigh.”)
“Physicians typically use BMI to measure a patient’s ‘weight health,’” explains Stewart Lonky, MD, in his book, Outsmarting Obesity: A Doctor Reveals Why We Gain Weight, Why It Matters, and What We Can Do About It.
Yet BMI is a blunt tool with significant limitations. It was first developed in the early 19th century — and updated by physiologist Ancel Keyes in 1972 — strictly as a research tool for measuring weight trends in populations. Neither of its creators were medical professionals, and they never intended BMI for medical use.
It was first developed in the early 19th century — and updated by physiologist Ancel Keyes in 1972 — strictly as a research tool for measuring weight trends in populations. Neither of its creators were medical professionals, and they never intended BMI for medical use.
The original study in which BMI was used didn’t include women and most of its participants were white men. This means its current status as a universal metric misdiagnoses a wide diversity of body types.
Most importantly, BMI reveals nothing about body composition. “The most significant drawback of BMI is its inability to differentiate between fat and muscle,” explains Lonky. “While it’s not accurate to say that muscle weighs more than fat, it is denser. This density is why a cubic inch of muscle weighs more than a cubic inch of fat.”
In a recent paper published in The Lancet Diabetes and Endocrinology, a commission of global experts argue that BMI-based definitions lead to overdiagnosis and underdiagnosis, labeling people as unhealthy when they aren’t and missing those who may be at risk despite a “normal” BMI. This can result in poorer health outcomes for everyone.
For example, a fit, muscular athlete might have a BMI over 30, qualifying them as obese strictly because of their weight-to-height ratio. On the other hand, someone with a “healthy” BMI of less than 25 might have metabolically active visceral fat (more on why that matters later) that puts them at risk for cardiovascular disease.
In neither case does their BMI explain anything about their actual health status.
Does the location of fat matter?
Where fat is stored may be more indicative of its risks than weight alone. “BMI tells you nothing about body composition or where you’re putting on weight,” explains holistic nurse practitioner Monique Class, MS, APRN-BC.
Visceral fat stored around vital organs in the abdomen appears to be particularly risky. Unlike subcutaneous fat, which is stored under the skin, visceral fat is sometimes described as “metabolically active” because it can produce hormones and inflammatory molecules. Fat around the midsection has been associated with systemic inflammation, insulin resistance, and cardiovascular risks.
Visceral fat can also be an indication of metabolic syndrome, a cluster of conditions — including high blood pressure, high blood triglycerides, low levels of HDL cholesterol, and insulin resistance — that occurs together. Metabolic syndrome increases a person’s risk of heart disease, stroke, and type 2 diabetes. (Learn more about visceral fat in “Anatomy of a Potbelly.”)
What is “metabolic obesity”?
The global commission of experts involved in The Lancet Diabetes and Endocrinology report recommend defining obesity through clinical signs — such as tissue and organ alterations — that better capture when excess fat genuinely impacts health. This definition ensures a more precise identification of those in need of intervention and could lead to more effective treatment.
This approach acknowledges that caloric intake or physical-activity level are not the only factors influencing a person’s metabolic health. Chronic stress, sleep quality, thyroid health, hormone regulation, gut health, and genetics all play an important role. Understanding the root causes of disruptions in metabolic health would be the focus of any intervention.
By this definition, a thin person with metabolic syndrome could be classifiably obese while a heavier person may or may not. What matters most are factors like insulin regulation, blood pressure, and cardiovascular function.
By focusing on metabolic health, clinicians can identify and address issues such as hormonal imbalances and the role of visceral fat in driving inflammation and cardiovascular risks.
Are there other ways to classify higher weight and obesity?
Some researchers classify weight metabolically using these phenotypes:
- Metabolically Unhealthy Normal Weight: People who have a BMI of between 18.5 and 24.9 but exhibit metabolic problems commonly associated with obesity or metabolic syndrome, such as insulin resistance and high blood pressure. Despite their lower weight, these individuals may face health risks due to underlying metabolic dysfunction.
- Metabolically Unhealthy Obesity (MUO): Individuals with high weight and additional metabolic complications, such as high blood pressure, insulin resistance, and abnormal cholesterol levels. MUO is associated with higher risks for cardiovascular disease and type 2 diabetes.
- Metabolically Healthy Obesity (MHO): People with a BMI over 30 without metabolic risk factors typically linked to obesity. Even if a person categorized as MHO has healthy metabolic markers, it’s important to manage those markers over time by remaining active and eating a quality diet. While MHO offers a lower immediate risk, studies have shown that up to 50 percent of individuals with MHO develop metabolic complications within a decade or so, driven by aging, weight gain, and declining insulin sensitivity.
Weight is only one aspect of overall metabolic health, so it’s important to recognize that the number on the scale tells the whole story. It makes perfect sense to question an obesity diagnosis, especially if it’s based on BMI, if you know you’re healthy, rested, and strong. The metabolic numbers are the ones that count.
This Post Has 0 Comments