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BMI can tell us how heavy someone is relative to their height. It cannot, by itself, tell us how much body fat they have, where that fat is stored, whether their organs are being affected—or how well they can function. Modern obesity care needs to ask all of those questions.
For decades, one calculation has dominated the conversation about obesity:
Weight in kilograms ÷ height in metres² = BMI.
A result below 25? “Normal.”
Between 25 and 29.9? “Overweight.”
Thirty or above? “Obesity.”
The simplicity is attractive.
But human biology is not that simple.
Consider three people.
One has a BMI of 31 kg/m², substantial muscle mass, relatively low body fat and no evidence of obesity-related organ dysfunction.
Another also has a BMI of 31, but carries substantial abdominal and visceral adiposity, has hypertension, metabolic dysfunction and obstructive sleep apnoea.
A third has a BMI of 24—technically within the conventional “normal” range—but has low muscle mass, substantial abdominal adiposity and impaired glucose regulation.
If BMI is the only measurement used, the first two people appear essentially identical while the third may appear reassuringly low-risk.
Clinically, they may be very different.
This is the problem modern obesity medicine is trying to solve.
In 2025, a global commission published in The Lancet Diabetes & Endocrinology proposed a major reframing of how obesity should be defined and diagnosed. The Commission argued that BMI alone is insufficient for diagnosing obesity at the individual level and proposed distinguishing the presence of excess adiposity from the question of whether that adiposity is already producing illness or functional impairment.[1]
That does not mean BMI has become useless.
It means we need to stop asking one number to answer questions it was never designed to answer.
BMI is a ratio of weight to height.
That is all.
It does not directly measure body fat.
It does not distinguish:
Two people of identical height and weight therefore have identical BMIs even if their body composition is profoundly different.
This is why a highly muscular athlete can have a BMI classified as overweight—or occasionally obese—despite having relatively low body fat.
The reverse can also occur.
An older adult who has lost substantial skeletal muscle may have a BMI in the conventional “normal” range while carrying a relatively high proportion of body fat.
BMI measures body size reasonably well. It measures individual adiposity much less precisely.
That distinction matters because obesity is fundamentally about excess adiposity and its consequences, not simply body weight.
Because BMI does have important strengths.
At population level, BMI is strongly associated with many health outcomes and remains valuable for epidemiological surveillance, research and initial risk screening.
The problem arises when a screening measurement becomes treated as a complete diagnosis.
Think about blood pressure.
A single blood-pressure reading can provide valuable information. But responsible clinical care does not interpret that number without context.
BMI deserves the same approach.
Use it as an entry point—not necessarily the final answer.
One of the most important contributions of the 2025 Lancet Commission is separating BMI from adiposity.[1]
BMI can suggest that excess body fat is likely.
But at an individual level, clinicians may need additional evidence.
Why?
Because where fat is stored matters.
Fat stored predominantly beneath the skin is not metabolically identical to fat accumulated around abdominal organs or deposited ectopically in organs such as the liver.
This brings us to one of the most clinically useful measurements that is still surprisingly underused.
Waist circumference provides information about central or abdominal adiposity.
That matters because greater visceral adiposity is associated with cardiometabolic risk.
An American Heart Association scientific statement emphasized that waist circumference and other measures of central adiposity can provide risk information beyond BMI. At a given BMI, greater central adiposity is associated with higher cardiovascular risk.[2]
This means two people with a BMI of 27 may not have equivalent risk.
One may carry relatively little abdominal fat.
The other may have pronounced central adiposity.
BMI alone cannot distinguish them.
A 2025 global analysis made this limitation particularly striking: more than one in five adults classified as having a normal BMI had abdominal obesity.[3]
In other words:
A “normal” BMI does not automatically mean a low-risk body-fat distribution.
This is particularly relevant in populations that can develop metabolic risk at comparatively lower BMI values, including many South Asian populations.
For an Indian clinical audience, that point deserves particular attention.
Waist measurements are practical.
More sophisticated methods can provide further information.
Depending on clinical circumstances, body composition can be estimated or measured using technologies such as:
DXA
Dual-energy X-ray absorptiometry can estimate total and regional fat mass and lean mass.
Bioelectrical impedance
Widely available and convenient, although accuracy can vary according to device quality, hydration and testing conditions.
CT or MRI
These can quantify visceral and ectopic adipose tissue with considerable precision, although cost, accessibility and—in the case of CT—radiation exposure limit their use for routine obesity screening.
These tools are not required for every patient.
Body weight is not body composition.
That distinction becomes especially important when someone is losing weight.
A 10-kg reduction that predominantly reflects fat loss while preserving skeletal muscle is physiologically different from a 10-kg reduction accompanied by substantial loss of lean tissue.
The scale cannot show that distinction.
BMI cannot either.
The Lancet Commission proposed an even more significant change.
After confirming excess adiposity, it asks whether that adiposity is actually causing disease or functional impairment.[1]
Preclinical Obesity
This describes excess adiposity in a person who does not currently have ongoing organ dysfunction or significant limitation of daily activities attributable to obesity.
That does not mean “nothing is wrong.”
Excess adiposity may still increase the future risk of developing disease.
The clinical emphasis may therefore include risk assessment, prevention, monitoring and individualized management.
Clinical Obesity
This refers to obesity accompanied by signs or symptoms of ongoing organ dysfunction and/or significant limitations in daily activities attributable to excess adiposity.[1]
This distinction shifts the conversation dramatically.
Instead of:
“Your BMI is 32, therefore your disease is defined by 32.”
Those are much more clinically meaningful questions.
When people hear “obesity complications,” they often think only of diabetes.
The consequences can be much broader.
The important point is not to create an enormous checklist of everything associated with obesity.
It is to recognize that the clinical significance of adiposity is expressed through health and function—not through BMI alone.
This concept requires nuance.
Some people with BMI-defined obesity have normal blood pressure, glucose and lipid measurements at a particular point in time.
They are sometimes described as having metabolically healthy obesity.
This demonstrates why BMI alone does not tell us someone’s current metabolic status.
But “metabolically healthy” should not automatically be interpreted as risk-free.
Health status can change over time, and metabolic blood tests are only one dimension of obesity-related health.
The newer clinical framework is useful precisely because it asks us to look beyond both extremes:
A high BMI does not automatically tell us how sick someone is.
But:
Normal blood tests today do not necessarily mean excess adiposity is clinically irrelevant forever.
Risk exists on a continuum.
The opposite misconception may be even more important.
Research on normal-BMI abdominal obesity demonstrates precisely why this group can be missed when BMI is treated as the sole gatekeeper for metabolic assessment.[3]
“But I’m not overweight, so why is my blood sugar high?”
Because body weight is only one part of metabolic health.
Genetics, fat distribution, muscle mass, physical activity, diet, sleep, medications, age and numerous other factors contribute.
Thinness is not immunity from metabolic disease, just as a higher body weight is not a complete diagnosis of metabolic dysfunction.
Another important example is sarcopenic obesity—the coexistence of excess adiposity with low muscle mass and/or impaired muscle function.
Imagine an older adult who has progressively lost skeletal muscle while accumulating body fat.
Their total body weight may not change dramatically.
BMI may barely move.
Yet body composition and physical resilience may deteriorate substantially.
This has major implications for weight-management treatment.
If the sole goal becomes:
“Make BMI smaller as quickly as possible,”
an aggressive weight-loss strategy could potentially worsen lean-tissue loss.
A better strategy asks:
Are we reducing excess fat while preserving muscle, strength and function?
This is why adequate protein, resistance exercise and functional assessment matter in modern weight-management care.
The quality of weight loss matters—not only the quantity.
This is where the conversation can swing too far.
Recognizing BMI’s limitations does not require pretending it has no value.
At very high BMI values, the probability of excess adiposity is also high.
The mistake is not using BMI.
The mistake is using only BMI when the clinical question requires more information.
A better model is:
BMI → Adiposity → Distribution → Complications → Function
Each step answers a different question.
That is a far richer clinical picture than a single category printed on a chart.
There is no single test that captures every dimension of obesity.
But a more clinically useful assessment may include several domains.
1. Body size
Weight, height and BMI remain useful starting measurements.
2. Central adiposity
Waist circumference—and in appropriate settings waist-to-height or waist-to-hip ratio—can add information about abdominal fat distribution.[1,2]
3. Body composition when clinically useful
Assessment of fat mass and lean mass can be valuable in selected patients, especially when muscle loss, sarcopenia or unusual body composition is suspected.
4. Cardiometabolic health
Depending on clinical context:
5. Obesity-related conditions
Assessment may include sleep apnoea, liver disease, osteoarthritis, reproductive/metabolic disorders and other relevant complications.
6. Physical function
Can the person climb stairs comfortably?
Walk meaningful distances?
Perform daily activities?
Maintain strength?
Function can reveal clinical burden that a BMI category cannot.
7. Nutrition and behaviour
Diet quality, restrictive eating, protein adequacy, food access, alcohol intake, physical activity, sleep and previous weight-management experiences matter.
8. Psychological and social context
Weight stigma, eating disorders, mental health, medications, socioeconomic conditions and environmental factors can profoundly affect both obesity and its treatment.
A clinically useful obesity assessment therefore looks less like a calculation and more like a health evaluation.
If obesity is reduced to BMI, nutrition care easily becomes:
“Your BMI is high. Eat fewer calories until it becomes normal.”
That approach is increasingly inadequate.
Two people with identical BMI may require completely different priorities.
Patient A
BMI 32, hypertension, insulin resistance, abdominal adiposity and fatty liver.
Nutrition goals may prioritize clinically meaningful fat loss, dietary quality, cardiometabolic improvement, adequate protein and sustainable energy reduction.
Patient B
BMI 32, physically active, relatively favourable metabolic markers and no clear current obesity-related dysfunction.
The intensity, goals and risk-benefit discussion may differ.
Patient C
BMI 23, significant abdominal adiposity, low muscle mass and impaired glucose regulation.
Telling this person that their BMI is “normal” may provide false reassurance.
Nutrition care may need to focus on body composition, resistance exercise, dietary quality and cardiometabolic risk rather than simply weight loss.
Patient D
BMI 29 and actively losing weight on GLP-1 therapy, but also losing strength and consuming very little protein.
Here, pushing for the lowest possible BMI could be the wrong immediate nutrition priority.
Protecting muscle and nutritional adequacy may matter more.
Good nutrition care treats the person—not the BMI category.
For populations in India and across South Asia, the limitations of universal BMI interpretation are especially relevant.
Cardiometabolic risk can occur at comparatively lower BMI values in many Asian populations, partly reflecting differences in body composition and visceral adiposity.
This is one reason ethnicity- and population-specific thresholds have been considered in diabetes and metabolic-risk screening.
The clinical lesson is not that every South Asian person with a lower BMI has metabolic disease.
It is that:
BMI thresholds cannot substitute for actual risk assessment.
Waist measurement, family history, blood pressure, glucose regulation, lipid profile, physical activity and other risk factors may identify clinically important risk that conventional BMI categories miss.
There is another reason to move beyond BMI.
A number on a chart can quickly become a judgement about a person.
Those assumptions are not a clinical assessment.
Obesity is influenced by complex interactions involving biology, genetics, neuroendocrine regulation, medications, sleep, environment, socioeconomic circumstances, mental health and many other factors.
Weight stigma can also damage healthcare itself.
Patients may delay appointments, avoid screening or disengage from treatment after stigmatizing experiences.
Moving beyond BMI therefore does not mean ignoring obesity.
It means taking obesity more seriously as a clinical condition and less seriously as a moral judgement.
That is an important distinction.
For some patients, meaningful weight loss can improve glucose control, blood pressure, mobility, sleep, liver health and quality of life.
But successful obesity care should not necessarily be defined by whether someone eventually enters the conventional “normal BMI” category.
A person may experience major improvements in health while remaining above BMI 25.
Another person may reach a lower BMI while losing substantial muscle, developing nutritional inadequacy or engaging in unsustainable restriction.
This is why outcome measures should extend beyond kilograms.
The scale matters.
It just should not be the only outcome that matters.
BMI gave healthcare something enormously useful:
A simple, inexpensive way to describe body size.
The problem began when that description became mistaken for the whole disease.
At The NIND Knowledge Hub, we believe the future of obesity nutrition should move from:
“What is your BMI?”
Toward:
“What is happening to your health?”
The 2025 Lancet Commission did not make BMI irrelevant.[1]
It placed BMI where it belongs:
Inside a clinical assessment rather than above it.
This distinction can improve care in both directions.
It can prevent overdiagnosis based purely on body size when BMI does not accurately represent adiposity.
And it can prevent under-recognition of risk in people whose BMI appears “normal” despite harmful abdominal adiposity or metabolic dysfunction.
Most importantly, it shifts obesity care away from a simplistic pursuit of smaller bodies.
The clinically useful question is not simply “How much do you weigh?”
It is “How is adiposity affecting your health—and what can we meaningfully improve?”
That is a more sophisticated question.
It is also a more humane one.
And increasingly, it is the question modern obesity care needs to answer.
Dt. Neha Vijh
Certified Clinical Dietitian | Women’s Health Expert | Founder & Director – NIND
Internationally Certified PCOS Coach | Internationally Certified Dietary Supplement Practitioner
India
Dt. Neha Vijh works across clinical nutrition, women’s health, PCOS and evidence-informed nutrition practice. Her work emphasizes translating nutrition and metabolic-health science into practical clinical frameworks while moving beyond oversimplified weight- and diet-based narratives.
As Founder & Director of NIND, she contributes to NIND’s mission of strengthening evidence-informed nutrition education and helping nutrition professionals interpret evolving clinical research responsibly.
The NIND Knowledge Hub is the evidence-focused nutrition education and professional knowledge platform of NIND, created to bridge the gap between nutrition research, clinical practice and understandable health information.
Its Clinical Insights examine emerging and evolving areas of nutrition science with an emphasis on clinical relevance, evidence interpretation and responsible translation into practice.
Evidence interpreted. Nutrition understood. Practice improved.
This article is intended for educational and professional-information purposes and does not constitute an individual diagnosis or personalized medical, dietetic or weight-management treatment plan.
BMI, waist circumference, body-composition measurements and metabolic markers all require interpretation in clinical context. No single measurement should be used in isolation to determine an individual’s health, treatment eligibility or prognosis.
People concerned about weight, abdominal adiposity, metabolic health or obesity-related complications should seek assessment from appropriately qualified healthcare professionals.
Weight-management treatment should consider medical history, medications, nutritional status, physical function, psychological health, individual preferences and the presence or risk of obesity-related complications.
Published by The NIND Knowledge Hub
Clinical Insight | Weight Management
Author: Dt. Neha Vijh, Certified Clinical Dietitian
India
Evidence • Nutrition • Clinical Practice • Professional Growth
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