Nearly seven out of 10 U.S. adults now meet the criteria for obesity under a new, more comprehensive definition tested in JAMA Network Open.1 The new standard — previously proposed by an international panel of experts in The Lancet Diabetes & Endocrinology2 — goes beyond body mass index (BMI) to include waist and hip measurements that reveal hidden fat conventional BMI misses.
By doing so, it captures millions of Americans whose weight appears “normal” but whose fat distribution signals a higher risk for metabolic disease. Obesity means more than simply carrying extra weight — it reflects a buildup of body fat that disrupts how your cells use energy. Even with a normal BMI, fat that gathers deep in your abdomen and around your organs releases inflammatory chemicals that impair insulin function, raise blood pressure, and strain your heart and liver.
These effects often unfold silently for years, showing up as fatigue after meals, creeping blood sugar, or blood pressure that refuses to normalize. For decades, BMI alone dictated whether someone was labeled obese. But that narrow measure overlooks where fat is stored — and that’s where the real danger lies. By incorporating waist and hip data, the JAMA Network Open study uncovered a hidden epidemic of “normal-weight obesity,” especially among older adults.
This shift is a wake-up call. Your waistline offers a clearer window into your metabolic health than the scale ever could. Understanding this new definition helps you see why a healthy weight doesn’t always mean a healthy body, and why measuring fat where it matters most could change how you protect your long-term health.
New Definition Reveals Hidden Obesity in Millions of Americans
Obesity has long been defined almost entirely by BMI — a simple calculation using weight and height. But BMI alone doesn’t show where fat is stored or how it affects your health. To fix this, an international commission of experts from multiple medical specialties proposed a new definition published in The Lancet Diabetes & Endocrinology.3
Endorsed by at least 76 professional organizations worldwide, this new guideline classifies obesity using not just BMI but also additional measures, such as waist and hip measurements, or direct scans of body fat. It also distinguishes between clinical obesity, where fat is already harming organs, and preclinical obesity, where fat buildup has begun but damage isn’t yet visible. This change marks a major shift in how doctors and researchers identify who’s truly at risk.
• The JAMA Network Open study tested the new definition of obesity — This large-scale analysis applied the Lancet-based criteria to real-world data from 301,026 U.S. adults in the National Institutes of Health’s All of Us cohort. The goal was to see how this expanded definition would change obesity classification and reveal previously hidden health risks across diverse populations.
• Significant increase in obesity under new definition — Using only BMI, 42.9% of adults were categorized as obese. But when the new Lancet-based definition was applied, 68.6% met the criteria — a 60% surge in national obesity prevalence.
This increase was driven by those with “anthropometric-only obesity,” meaning individuals whose BMI fell within the normal or overweight range but whose waist circumference, waist-to-hip ratio, or waist-to-height ratio indicated excess central or visceral fat.
• The findings revealed a major blind spot in conventional BMI screening — About 1 in 4 adults were reclassified as obese under the new definition, mostly from the overweight category, while roughly 1 in 17 had a normal BMI yet carried hidden visceral fat that increased their risk for metabolic disease.
These individuals faced significantly higher risks of diabetes, cardiovascular disease, and organ dysfunction. This means someone could look lean on the outside while silently developing metabolic damage inside — a reality BMI fails to capture.
• The study confirmed two obesity subtypes carry distinct health risks — Building on Lancet’s redefinition framework, researchers divided participants into those obese by both BMI and body measurements and those obese by body measurements alone.
Both subtypes showed increased rates of organ dysfunction, but the severity differed. The BMI-plus group showed more advanced disease, while the measurement-only group displayed early metabolic imbalances that often precede chronic illness.
Clinical and Preclinical Obesity Describe Two Stages of Metabolic Decline
Clinical obesity refers to measurable organ damage, while preclinical obesity signals early dysfunction before damage occurs. The JAMA analysis showed that clinical obesity carried over sixfold higher risk for diabetes and nearly sixfold higher risk for cardiovascular events compared with non-obese adults. Even those with preclinical obesity had triple the diabetes risk, underscoring the importance of catching fat-driven metabolic dysfunction early.
• Older adults and men experienced the largest jump in obesity classification — Using the new framework, 78% of Americans aged 70 and older met the criteria for obesity — double previous estimates. Men were more likely to fall into the measurement-only category, likely due to age-related hormone shifts, muscle loss, and central fat accumulation. These findings highlight that weight stability with age does not guarantee metabolic health.
• Fat distribution, not total weight, drives metabolic danger — The study reinforced that visceral fat — the type that wraps around organs — is far more harmful than subcutaneous fat under the skin. Visceral fat is metabolically active, releasing inflammatory cytokines and fatty acids. This damages mitochondria, lowering their ability to generate cellular energy.
The resulting oxidative stress disrupts insulin balance and sets the stage for diabetes, fatty liver, and heart disease — a chain reaction that unfolds quietly over time. Two people with identical BMIs can have completely different risk profiles depending on where their fat is stored.
• The concept of “preclinical obesity” provides an early warning — By identifying those with unhealthy fat distribution before organ damage occurs, the new classification creates an opportunity for early intervention. You don’t need to wait for abnormal lab results — your waist-to-hip ratio alone helps reveal whether your cells are under metabolic stress.
• Your waistline tells the truth your BMI hides — The JAMA researchers concluded that BMI alone no longer captures true obesity risk. Adding waist-to-hip and waist-to-height ratios gives a clearer picture of your health, empowering you to take action before silent metabolic changes harden into chronic disease. For anyone who thought a “normal” BMI meant safety, this study proves it’s time to measure more than the scale.
Why BMI Misleads — and What to Measure Instead
• BMI oversimplifies a complex condition — BMI is a quick formula — weight divided by height squared — but that simplicity is also its biggest flaw. BMI alone fails to distinguish between fat and muscle, or between harmful visceral fat and harmless subcutaneous fat. This means that athletes or people with high muscle mass are often labeled as obese, while those with dangerous fat hidden deep around their organs are missed entirely.
• BMI misdiagnosis harms both over- and under-identified patients — Those misclassified as obese based on BMI alone are often pushed into unnecessary diets, medications, or even surgeries despite having healthy metabolism.
On the other hand, those whose BMI looks “normal” but who harbor excess visceral fat are left untreated — until they develop diabetes, cardiovascular disease, or other chronic conditions that could have been prevented. Misclassification has real-life health and emotional consequences.
• Your waist-to-hip ratio tells a more accurate story — The Lancet commission and the JAMA Network Open researchers agree that simple body measurements — especially waist and hip size — paint a clearer picture of your metabolic health. To get the ratio, divide your waist measurement by your hip measurement, then use the values below for reference:
| Waist-to-Hip Ratio | Men | Women |
|---|---|---|
| Ideal | 0.8 | 0.7 |
| Low Risk | <0.95 | <0.8 |
| Moderate Risk | 0.96 – 0.99 | 0.81 – 0.84 |
| High Risk | >1.0 | >0.85 |
Another measurement you can use is the waist-to-height ratio. To calculate the value:
• Waist-to-height formula — Divide your waist circumference by your height, making sure both measurements are in the same unit, either inches or centimeters. For example, if your waist measures 32 inches and your height is 64 inches, your waist-to-height ratio would be 0.50 (32 ÷ 64 = 0.50).
• The ideal ratio for adults — An ideal waist-to-height ratio for adults falls between 0.40 and 0.49, indicating a healthy range.4 A ratio below 0.40 suggests being underweight, while a ratio between 0.50 and 0.59 indicates excess weight and an increased risk of metabolic and cardiovascular diseases. A ratio of 0.60 or higher signals obesity and a significantly higher health risk.
• Don’t forget your child’s ratio — It’s also wise to check on your child’s waist-to-height ratio from time to time. For children ages 6 to 18, a ratio below 0.46 is considered healthy, while anything above this threshold suggests an increased risk of obesity-related health issues.
5 Steps to Restore Your Metabolism and Reverse Hidden Obesity
If you’ve been frustrated by stubborn weight gain or chronic diseases — even though your BMI looks “normal” — your body isn’t broken. It’s just stuck in energy-storage mode. The real problem isn’t a lack of willpower or motivation; it’s cellular energy failure.
When your mitochondria — the power plants inside your cells — are poisoned by modern foods and environmental toxins, your metabolism slows, fat accumulates, and energy disappears. You can fix it by giving your cells what they need to burn fuel efficiently again.
1. Cut vegetable oils and ultraprocessed foods — The first and most powerful thing you can do to restore your metabolism is to stop feeding it the wrong fuel. Vegetable oils — like canola, soybean, corn, sunflower, safflower, and grapeseed — are loaded with linoleic acid (LA), a polyunsaturated fat that clogs your mitochondria and traps you in fat storage mode when consumed in excess.
These oils hide in almost every restaurant meal, salad dressing, and “healthy” processed snack. Replace them with real, stable fats such as grass fed butter, ghee, or tallow. Avoid chicken and pork, which are also high in LA, and choose grass fed beef or lamb instead.
Your target is less than 5 grams of LA daily, ideally under 2 grams. To track your intake, I recommend you download my Mercola Health Coach app when it’s available this year. It has a feature called the Seed Oil Sleuth, which monitors your LA intake to a tenth of a gram so you can stay in charge of your metabolism.
Along with eliminating vegetable oils, remove ultraprocessed foods from your daily routine. These engineered products are designed to hijack your brain’s reward centers and make you eat more. Cooking at home gives you full control of your ingredients and resets your body’s natural hunger signals. Reading labels becomes your defense — if it has seed oils, additives, or mystery ingredients, it’s not serving your health.
2. Eat enough healthy carbs to heal your gut and fuel your cells — Your metabolism runs on glucose, and glucose comes from carbohydrates. The problem isn’t carbs themselves — it’s the wrong kind in the wrong gut environment. When your gut lining is inflamed, it leaks bacterial toxins into your bloodstream, slowing mitochondrial function. If you feel bloated or drained after meals, that’s a sign your microbiome is struggling.
Start with easy-to-digest carbs like fruit and white rice to calm inflammation. Once your digestion improves, slowly bring back root vegetables, then legumes, and later, whole grains. Aim for around 250 grams of healthy carbs daily. This level supports thyroid function, balances stress hormones, and helps your cells recover from years of under-fueling.
Think of it as repairing the engine instead of starving it. When your gut heals, beneficial bacteria produce butyrate, a short-chain fatty acid that strengthens your intestinal lining, improves mood, and keeps cravings under control.
3. Lower your exposure to estrogen and endocrine disruptors — Hidden estrogen overload keeps your metabolism sluggish and promotes fat gain, especially around the waist. It affects both men and women by throwing off thyroid and progesterone balance. Ditch plastics altogether — no more heating food in plastic containers or drinking from disposable bottles.
Store food in glass or stainless steel instead. Skip chemical-based personal care items and avoid touching thermal paper receipts whenever possible. Using natural progesterone helps counter excess estrogen, stabilizing your mood, energy, and metabolism.
4. Reduce electromagnetic field (EMF) exposure to protect your cellular energy — Phones, Wi-Fi, and Bluetooth devices constantly emit EMFs that stress your cells. EMFs force calcium into your mitochondria, slowing their energy output. To protect your energy system, turn off Wi-Fi at night, keep your phone on airplane mode while you sleep, and use wired connections whenever possible.
Ditch wireless earbuds — they beam EMFs directly into your head. These small habits lower oxidative stress, helping your cells repair and recharge during sleep.
5. Move daily to amplify your body’s ability to burn energy — Movement multiplies the benefits of these changes. Even simple daily motion — walking, stretching, and resistance training — improves insulin sensitivity and teaches your cells to burn glucose again. If you spend most of your day sitting, try setting a timer to stand up or walk for two minutes every half hour.
Think of every step as a signal to your mitochondria: “Make energy, not fat.” Over time, this combination of clean fuel and consistent motion retrains your body to burn energy efficiently. Ideally, work your way up to one hour of walking daily.
FAQs About the New Definition of Obesity
Q: What’s the main takeaway from the new obesity definition?
A: The new definition, introduced by experts in The Lancet Diabetes & Endocrinology5 and tested in JAMA Network Open,6 moves beyond BMI and includes waist and hip measurements to identify people with dangerous visceral fat. Under this expanded definition, about 69% of U.S. adults now qualify as obese — up from 43% under BMI alone. The shift exposes millions with “hidden obesity,” whose normal BMI conceals high-risk fat distribution and early signs of metabolic dysfunction.
Q: Why is BMI not a reliable way to measure obesity?
A: BMI only compares weight to height — it doesn’t show how much of that weight is fat, where fat is stored, or whether it’s harming your organs. As a result, muscular people are often mislabeled as obese, while others with normal BMI but excess abdominal fat go undiagnosed. The new approach focuses on function — how fat affects your metabolism and organs — rather than a single number on the scale.
Q: What are clinical and preclinical obesity?
A: Clinical obesity refers to excess body fat that’s already damaging organs or causing disease, such as diabetes or fatty liver. Preclinical obesity means excess fat has accumulated, but organ function remains normal — yet early metabolic changes have started. Identifying preclinical obesity allows you to intervene before lasting damage occurs.
Q: How can I measure my true obesity risk at home?
A: Two simple ratios provide a clearer picture of your metabolic health than BMI:
• Waist-to-hip ratio — Divide your waist by your hip measurement. A ratio above 1.0 in men or 0.85 in women indicates high visceral fat.
• Waist-to-height ratio — Divide your waist circumference by your height (in the same unit). A ratio of 0.50 or higher signals elevated metabolic and cardiovascular risk. Tracking these numbers helps you identify hidden fat before it leads to disease.
Q: What steps can I take to reverse hidden obesity and restore my metabolism?
A: You can dramatically improve metabolic health by addressing the causes of fat dysfunction — not just calories.
• Eliminate vegetable oils and ultraprocessed foods high in LA.
• Eat whole, nutrient-rich meals with adequate healthy carbohydrates to fuel your cells.
• Reduce exposure to plastics, endocrine disruptors, and synthetic estrogens.
• Minimize EMF exposure from Wi-Fi, phones, and Bluetooth devices.
• Move daily — walking, stretching, or resistance training — to retrain your cells to burn energy instead of storing it. Together, these strategies help your body shift out of fat-storage mode, restore energy balance, and lower your risk for metabolic disease — whether or not your BMI says you’re obese.
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