Imagine going to your doctor and hearing that nearly 7 in 10 American adults – possibly including you – are now considered obese. It sounds alarming, but that’s exactly what a new definition of obesity suggests. Health experts are redefining obesity by looking beyond the scale, and the results are astounding. As Dr. Lindsay Fourman of Massachusetts General Hospital put it, “We already thought we had an obesity epidemic, but this is astounding”sciencedaily.com. Under these updated criteria, the U.S. obesity rate would jump from about 40% to almost 70% of adults. This dramatic increase stems from a crucial insight: where fat is stored may be just as important as how much you weigh. In this article, we’ll break down the new obesity guidelines, why they matter for your health, and what they mean for the nation’s health policy.
Why BMI Alone Falls Short
For decades, obesity has been defined mainly by body mass index (BMI) – a simple ratio of weight to height. BMI is easy to calculate, but it has a big flaw: it doesn’t distinguish fat from muscle or reveal where fat is distributed. Many of us know someone who is “skinny-fat” (normal weight but carrying unhealthy fat) or a muscular person classified as overweight by BMI. Relying on BMI alone can therefore miss people at risk. In fact, one recent analysis found that nearly 4 in 10 adults with a “normal” BMI actually had excess body fat when their waist measurements were taken into account abcnews.go.com. This means millions of Americans who thought their weight was fine might still have unhealthy levels of fat around their organs.
Medical experts have long recognized BMI’s limitations sciencedaily.com. High waist circumference or an “apple” body shape, for example, is known to raise risk for heart disease and diabetes even if BMI is normal. These hidden fat risks drove an international commission of doctors and researchers (the Lancet Diabetes & Endocrinology Commission) to propose a new definition of obesity in early 2025. The goal was to paint a more accurate picture of body fat and its health impacts by adding waist and body fat measures to the equation sciencedaily.com.
The New Obesity Definition: Beyond the Scale
So, what are the new obesity criteria? Under the updated guidelines, you would be classified as having obesity if you meet any of the following conditions jamanetwork.com:
- Extremely high BMI: A BMI over 40 (roughly 100 lbs or more above a healthy weight) automatically qualifies as obesity.
- BMI + Waist: A BMI in the obese range (≥30 for most groups) plus at least one elevated waist or body-fat measure – for example, a large waist circumference or high waist-to-hip or waist-to-height ratio. (These “anthropometric” measures capture belly fat and fat distribution.)
- Waist Measures Only: Even with a normal or overweight BMI, having two or more elevated waist or body-fat measures would count as obesity jamanetwork.com. In other words, someone of average weight but with two markers of high abdominal fat would be reclassified as obese under the new definition.
- Body Fat Scans: Direct evidence of excess body fat from a high-tech scan (like a DEXA body composition scan) can also diagnose obesity, regardless of BMI.
These criteria acknowledge that a “normal” scale weight isn’t always healthy if a person carries too much visceral or abdominal fat. The new framework also introduces two important subcategories: “preclinical” vs. “clinical” obesity. Preclinical obesity means a person has excess fat by the new definition, but no current obesity-related health problems. Clinical obesity means their excess fat has already led to health issues like diabetes, high blood pressure, or physical impairments jamanetwork.com. This distinction matters because it suggests not everyone with obesity needs the same urgency of treatment. The commission actually recommends focusing first on healthy lifestyle changes for those with preclinical obesity, reserving weight-loss medications or surgery for select cases. This is a big shift from traditional practice, where any BMI-based obesity might prompt aggressive treatment.
Pro Tip: Measure your waist circumference at home – it’s easy and tells you a lot about your health. For most men, a waist over 40 inches (102 cm) and for most women over 35 inches (88 cm) is considered high risk for obesity-related diseases nhlbi.nih.gov. Some experts also suggest keeping your waist-to-height ratio below 0.5 (your waist should be less than half your height). If your waist measurement is in the danger zone, talk to your doctor – even if your BMI looks “normal.”
An “Astounding” Surge to 70% Obesity Rate
When researchers applied these new criteria to real-world data, the results were eye-opening. A team at Mass General Brigham analyzed over 300,000 U.S. adults from the NIH “All of Us” health study and found that 68.6% met the new obesity definition, compared to 42.9% under the old BMI-only definition sciencedaily.com. In other words, the obesity prevalence jumped from roughly 4 in 10 adults to 7 in 10. Dr. Fourman, lead author of the study, called the increase “striking”. The surge was entirely due to people who previously slipped under the radar – individuals with “anthropometric-only obesity” (normal-BMI but high waist/body-fat measures). About 78,000 participants in that analysis had obesity by the new definition but would have been considered at a healthy weight by BMI alone.
Certain groups saw especially large jumps. Older adults were most affected – nearly 80% of Americans over age 70 fell into the obesity category with the new metrics sciencedaily.com. (We tend to lose muscle and gain fat as we age, even if the scale doesn’t change, so this isn’t entirely surprising.) Men and women had similar overall obesity rates, but men were more likely to be in the new “hidden obesity” group than women. And while obesity rose across all racial groups under the new definition, the relative increase was highest among Asian Americans, who often carry visceral fat at lower BMIs. These findings underscore that many people who appear “average” in size may actually have risky fat levels, depending on their age, sex, and ethnicity.
“We already thought we had an obesity epidemic, but this is astounding,” said Dr. Fourman upon seeing the new numbers. “With potentially 70 percent of the adult population now considered to have excess fat, we need to better understand what treatment approaches to prioritize.”sciencealert.com
Indeed, such a massive increase in obesity prevalence has far-reaching implications. It means tens of millions more Americans would be flagged for intervention if these guidelines are adopted. It also reframes our understanding of the obesity epidemic: it’s not just about obvious cases of high BMI – it’s also about the “hidden” obesity in people who might not know they’re at risk.
Higher Health Risks for “Hidden” Obesity
Why change the definition of obesity in the first place? Because these newly classified individuals aren’t truly healthy, many are at high risk of weight-related diseases even though a traditional BMI chart wouldn’t label them obese. The recent study confirmed that those with anthropometric-only obesity have significantly higher rates of type 2 diabetes, heart disease, and even mortality compared to people with no obesity sciencedaily.com. In fact, the health risk for this group, while lower than for those obese by both BMI and waist, was still substantial. About half of the newly labeled group already had “clinical” obesity – meaning signs of organ damage or illness related to their excess fat. As one researcher noted, this validates that “their classification as having obesity is clinically appropriate”. In plainer terms, many of these folks with “hidden fat” are suffering the same consequences as traditional obesity, like elevated blood sugar, fatty liver, or artery damage theguardian.com.
This evidence is actually reassuring in one sense: it shows the new definition is better at catching people who need help. The updated criteria identified people who BMI alone would have missed, and many of them already have or are developing health problems due to excess fat. As Dr. Steven Grinspoon, a Harvard endocrinologist, explained, “Seeing an increased risk of cardiovascular disease and diabetes in this new group of people with obesity, who were not considered to have obesity before, brings up interesting questions about obesity medications and other therapeutics.”. In other words, should some of these individuals start treatments like weight-loss medications even if their BMI isn’t high? It’s a tricky question that doctors and researchers are now grappling with.
On the flip side, about 52% of the people meeting the new obesity criteria were still in the “preclinical” stage (no obvious health issues yet). That presents an opportunity: if we identify these high-risk individuals earlier, we might help them prevent serious diseases through lifestyle changes or timely medical care. As Dr. Fourman noted, recognizing someone with a BMI of 23 but a high waist size means a doctor could encourage them to improve their diet and exercise before they become diabetic. In fact, “someone with BMI 23 but excess abdominal fat could benefit from lifestyle interventions such as improving diet and increasing physical activity, even though their BMI is in the ‘normal’ range”, Fourman said. Their physician might also keep an eye out for early problems like pre-diabetes or fatty liver in these patients theguardian.com. This proactive approach could be a game-changer for preventive health.
Key Health Risks of Excess Fat: Individuals classified as obese under the new guidelines face increased chances of:
- Type 2 Diabetes: Higher blood sugar and insulin resistance are more common in those with excess abdominal fat.
- Heart Disease & Stroke: Central obesity contributes to high blood pressure, cholesterol issues, and inflammation, elevating cardiovascular risk.
- Fatty Liver Disease: Extra visceral fat often infiltrates the liver, which can lead to non-alcoholic fatty liver disease and liver damage.
- Sleep Apnea & Joint Problems: Even in moderate amounts, excess fat around the trunk can worsen sleep apnea and put strain on joints.
- Higher Mortality: Studies show that carrying weight in the midsection is linked to higher overall mortality (death) risk, even if BMI is “normal”sciencedaily.com.
The silver lining is that reducing waist size and body fat can directly reduce these risks. It’s not just about a smaller number on the scale – it’s about less fat around your organs.
Implications for Healthcare and Policy
Labeling nearly 70% of American adults as “obese” is not just a medical reclassification – it’s a wake-up call for the healthcare system and society at large. Such a shift would have major implications for clinical practice, insurance coverage, and public health policy.
For one, doctors may need to start routinely measuring waist circumference and other body-fat indicators, not just height and weight. Many primary care visits today never include a waist measurement – that will likely change if these guidelines are adopted. Insurance and treatment guidelines might also evolve. Currently, eligibility for obesity treatments (like prescription weight-loss drugs or bariatric surgery) is largely based on BMI. If 70% of adults qualify as obese, clinicians will need to prioritize who truly needs intensive therapy. The commission behind the new definition emphasizes targeting “clinical obesity” cases for aggressive treatment and taking a more cautious approach for those in the preclinical stage jamanetwork.com. This nuanced strategy could prevent overwhelming the healthcare system by stratifying care – focusing resources (medications, specialist care) on those already suffering complications, while promoting diet, exercise, and close monitoring for others.
From a public policy perspective, the findings sound an alarm to strengthen obesity prevention efforts. As Professor Naveed Sattar (who was not involved in the study) noted, “Regardless of definitions, it’s clear that current obesity levels pose major challenges… underscoring the urgent need for more effective strategies to support healthier living.” Public health programs may need to broaden their scope to reach people who thought they were at a “healthy” weight but aren’t. For example, community health initiatives could offer waist circumference screenings or public awareness campaigns about the dangers of central obesity. Workplaces might include body composition checks in wellness programs. Schools could teach kids early on about body composition vs. body weight, so the next generation understands that a healthy body isn’t just about the scale.
Policymakers will also have to grapple with the sheer scale of the issue. If two-thirds of adults are obese by the new definition, obesity truly becomes a normative condition. This could reduce stigma (since it’s so common) but also increase urgency for systemic solutions. We might see calls for insurance to cover nutritional counseling or fitness programs for those at risk, since catching preclinical obesity early could save costs on diabetes or heart disease later. There may also be debates about updating food policies, urban planning, and other environmental factors to help people maintain healthier waistlines. Essentially, the new definition underscores that the obesity crisis is even bigger than we realized, and tackling it will require coordinated action in healthcare and policy.
On the other hand, some experts urge caution before rushing to adopt the new definition nationwide. The change would instantly label tens of millions more people as having a disease, which could have psychological impacts and resource implications. Researchers stress that more study is needed and that age-specific thresholds might be wise (since nearly all seniors over 50 fell into obesity by these criteria) abcnews.go.com. For now, at least 76 medical organizations around the world have endorsed the new guidelines – including the American Heart Association and The Obesity Society – signaling broad expert support for this paradigm shift. However, as of this writing, no government or health system has officially adopted the criteria yet sciencealert.com. This means your doctor might not formally diagnose “obesity” using these new measures just yet, but the momentum is building.
Turning Knowledge into Action
The prospect of 70% of Americans being classified as obese can sound discouraging, but it’s also empowering knowledge. It tells us that we need to pay attention not just to weight, but to our waistlines and body composition. For individuals, the takeaway is clear: you can be slim by BMI but still at risk, so take a closer look at your own numbers. Check your waist measurement, consider getting a body fat analysis if possible, and keep an eye on how your clothes fit around your midsection. If you’re carrying extra inches at the waist, now is the time to act with healthier eating and regular exercise. Even small reductions in waist size can improve your metabolic health.
For healthcare providers and policymakers, the message is a motivational one: there’s an opportunity to intervene earlier and more effectively. As obesity expert Dr. Fatima Cody Stanford noted, “We do have a major problem… this Lancet Commission gives us a sense of how significant it is and how much we need to be doing a better job of treating it”. That means training more clinicians in obesity medicine, scaling up prevention programs, and making sure our healthcare system is ready to support a healthier society abcnews.go.com.
Bottom line: The new obesity definition shines a spotlight on “hidden” fat and its risks. It challenges all of us to redefine what healthy looks like and to take action accordingly. Remember, “body composition matters – it’s not just pounds on a scale”. By focusing on reducing excess body fat (especially around the waist) through diet, exercise, and medical care when needed, we can improve health for millions of Americans. Nearly 70% obesity may sound intimidating, but with the right strategies, we can turn these numbers around – one inch at a time, one healthy choice at a time.
