Redefining Obesity: New Criteria Reveal Nearly 70% of U.S. Adults May Be at Risk

Key Takeaways

• A new definition of obesity incorporates anthropometric measurements, such as waist circumference and fat distribution, rather than relying solely on body mass index. 
• The new definition also categorizes obesity into clinical and preclinical categories, depending on the presence of organ dysfunction. 
• More Americans fit the criteria for obesity under this new definition, with real implications for metabolic health, early detection, and personalized monitoring.

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Obesity has long been defined by a single number: body mass index (BMI). But a new approach incorporating waist measurements, fat distribution, and organ dysfunction suggests a far greater portion of Americans may be at risk. This shift isn’t academic; it has real implications for metabolic health, early detection, and personalized monitoring.

What the New Definition of Obesity Entails

A 2025 report from The Lancet Diabetes & Endocrinology Commission proposed a new definition for obesity. The Lancet Commission report redefines obesity as a disease of excess or dysfunctional adiposity, not simply a high body mass index.¹ 

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The new diagnostic criteria include:

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• BMI greater than 40, or
• BMI plus anthropometric criteria: Elevated BMI and at least one anthropometric measurement (waist circumference, waist-to-hip ratio, and/or waist-to-height ratio), or
• Anthropometric-only obesity: At least two elevated anthropometric measurements with a normal BMI, or
• Excess body fat measurement confirmed through DEXA scan.² 

The new framework breaks down obesity into two categories, differentiated by obesity-associated organ dysfunction and/or physical limitation:

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• Preclinical obesity: Excess adiposity without documented organ dysfunction or physical limitation, but with an increased risk of developing clinical obesity and other chronic diseases.
• Clinical obesity: Excess adiposity with evidence of organ dysfunction and/or physical limitation.¹ 

This dual approach recognized that obesity isn’t just about body fat, but how that fat behaves metabolically.

Key Findings: The Scale of the Change

In a 2025 study published in JAMA Network Open, which included over 300,000 U.S. adults from the All of Us Research Program, 42.9% of participants met the traditional BMI definition of obesity. Under the new criteria, that number jumped to 68.6%, a nearly 60% increase.² 

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The biggest change came from the new anthropometric-only category, which captured individuals with normal BMIs but high body fat distribution.

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Other key findings:

• Roughly 1 in 4 participants met the new definition of obesity based solely on anthropometric measures. Among those individuals, 1 in 4 had a BMI in the traditionally normal range.
• Almost all individuals with obesity, based on the traditional definition, also met criteria for BMI-plus-anthropometric obesity per the new classification.
• Males were more likely than females to fit the criteria for anthropometric-only obesity.
• The largest relative increase in obesity prevalence occurred among Asian adults.
• The prevalence of obesity was higher among older individuals, with 78.3% of individuals 70 and older meeting the redefined obesity criteria.²

Why This Matters for Metabolic Health

Using body mass index to define obesity does not reflect your metabolic health. Anthropometric measures, such as waist circumference, provide greater insight into your metabolic health and what matters for long-term health.

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Anthropometric-only criteria indicate a higher risk of chronic conditions among individuals who would otherwise be missed if relying solely on the traditional definition. Compared to no obesity, people who met the anthropometric-obesity criteria had:

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• Twice the risk of developing type 2 diabetes
• A 55% higher risk of cardiovascular events
• A 20% higher risk of all-cause mortality² 

Meanwhile, individuals with clinical obesity (defined as obesity with organ dysfunction) exhibited a more than six times higher rate of diabetes and a 5.88 times higher rate of cardiovascular events than those with no obesity.²

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These new data highlight the health ramifications of excess body fat, regardless of BMI. Using anthropometric measurements enables earlier detection of excess adiposity and fat distribution, allowing for more timely lifestyle interventions, glucose monitoring, and personalized metabolic support.

What This Means for Individual Monitoring and Action

With this new definition, individual monitoring and action become more important as prevention strategies. No two individuals are alike, and this revised definition acknowledges the complexity of obesity. More than just the number on the scale matters for health. This new definition is not BMI-based but rather relies on body composition to assess health risk. 

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By incorporating preclinical obesity into the framework, the new definition opens the door to earlier, targeted lifestyle and nutrition interventions that can reverse or halt progression before chronic diseases develop.

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Focus on the following areas for prevention and health improvement:

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• Movement: Resistance training, walking after meals, and consistent daily activity improve insulin sensitivity.^3,4
• Nutrition: Prioritize balanced meals that include protein, fiber, and healthy fats to support stable glucose levels.⁵ 
• Recovery: Quality sleep and effective stress management can help reduce glucose variability.⁶ 

Continuous glucose monitors reveal the interaction between body composition and metabolic health. Elevated waist circumference or waist-to-hip ratios can reflect excess visceral fat, which is strongly linked with insulin resistance and glucose variability. Observing how glucose responds to meals, stress, or sleep deprivation helps connect what’s happening on the inside with what’s happening on the outside, such as fat distribution.

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Excess body fat, particularly abdominal fat, is a significant risk factor for developing type 2 diabetes and heart disease. Excess adiposity leads to insulin resistance and beta-cell dysfunction, contributing to the onset of diabetes.⁷ Obesity and type 2 diabetes are significant risk factors for cardiovascular disease. Obesity increases the risk of several cardiovascular diseases, with the risk sharply increasing with higher BMI and longer duration of obesity. Excess visceral fat disrupts heart function, contributing to changes in blood pressure and an increased risk of heart disease.^8,9   

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Redefining obesity means that nearly 70% of U.S. adults may now meet criteria for obesity, bringing greater urgency to early screening and prevention.² Personalized interventions that integrate continuous glucose insights with clinical measures, such as waist circumference, metabolic markers, and blood work, can help identify preclinical obesity before organ dysfunction develops.

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In practice, this means utilizing CGM data to monitor subtle glucose fluctuations, track improvements over time, and inform nutrition and lifestyle adjustments that promote long-term metabolic health.

Connecting the New Definition to Real-World Action with Signos

The new obesity framework highlights something Signos users already know: your health can’t be captured by a single number. BMI, body weight, and even waist measurements tell part of the story, but your glucose data reveals how your body is actually functioning in real time.

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With the Signos app, continuous glucose monitoring, and Signos’ adaptive insights, you can connect how daily choices influence your internal metabolism and identify early signs of metabolic dysfunction long before they appear in lab results.

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Here’s how Signos helps translate this new science into daily action:

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• Weekly Insights: See how your glucose stability evolves week to week, especially as you make small adjustments to meals or activity levels. Track progress over time with visual data summaries that help you and your healthcare provider identify trends linked to preclinical metabolic risk.
• Real-Time Glucose Feedback: Watch how your body responds to different foods, meal timing, or workouts, and use this feedback to optimize metabolic function, not just manage weight.
• Personalized Nudges: Get reminders when glucose rises too steeply, prompting you to take a short walk or hydration break to improve insulin sensitivity.

Experiments to Try When You Start Using Signos:

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• The Post-Meal Walk Test: After a carb-heavy meal, take a 10–15 minute walk and compare your glucose curve to days when you remain sedentary. You’ll often see a faster return to baseline, an early sign of improved metabolic flexibility.
• Protein-First Experiment: Try eating protein and fiber before carbs at one meal per day. Watch for a lower post-meal peak in your CGM graph (less time spent in yellow or pink zones).
• Sleep and Stress Correlation: Use the Signos app to note stress or sleep quality. Track whether poor sleep or stressful days correspond to higher fasting or overnight glucose levels.
• Fasting Window Check: Experiment with shifting your eating window earlier in the day. Many members find their glucose stabilizes (more purple zones) when dinner is moved up by even one hour.
• Weekend Reset: Compare weekday and weekend glucose patterns. Are higher readings linked to late meals, alcohol, or skipped movement? The Weekly Insights feature will help visualize these patterns clearly.

Each experiment helps you see how lifestyle factors influence glucose control, visceral fat accumulation, and long-term metabolic health, the very markers emphasized in the new obesity definition.

Limitations and Considerations

Although the Lancet Commission’s new obesity definition exists, it has yet to be applied in practice. Not all healthcare providers may be aware of the new framework, and public health guidelines and policy still revolve around BMI as a marker of health status.

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The new definition shifts away from body size alone and focuses on other health markers, encouraging clinicians to assess metabolic and physiological health more holistically, which may help reduce weight stigma.

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As obesity definitions evolve, insurance coverage and eligibility for obesity-related programs, pharmacotherapy, and nutrition services will need to adapt accordingly. 

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For individuals, this new definition of obesity means earlier awareness, more nuanced diagnosis, and potentially better prevention. For public health, it means more people qualify for intervention, and prevention strategies will need to start earlier, be more personalized, and focus on metabolic health outcomes rather than weight alone.

The Bottom Line

The way we define obesity is shifting, and with it, the number of Americans considered at risk is rising dramatically. Whether your BMI falls under the “traditional” or not categories, body-fat distribution and metabolic health matter.

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Monitoring glucose patterns, staying active, eating in a way that supports insulin sensitivity, and focusing on recovery are now more important than ever. With data-driven tools like Signos, you’re empowered to move beyond a single number and adapt your habits to your unique profile.

Learn More With Signos’ Expert Advice

The new definition of obesity emphasizes the importance of body fat distribution and metabolic function, highlighting that these factors are more significant than BMI alone. Signos’ continuous glucose monitors provide personalized monitoring and insight into your metabolic health, enabling early detection, so you can use data, not guesswork, to prevent obesity. Learn how Signos can improve health.

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Visit Signos’ expert-written blog to learn how glucose levels provide insight into long-term health.