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A global commission published in the Lancet Diabetes and Endocrinology looks at the definition and diagnosis of clinical obesity.
Dr Adam Collins, Associate Professor of Nutrition, University of Surrey, said:
“A very pertinent paper which highlights an important distinction between obesity as a marker of body mass for size, and obesity as a marker of health (or ill health). Drawing upon existing evidence, it is robustly laying bare the flawed assumption that body mass for size is, by itself, a marker of health.
“Whilst BMI is presumptively an index of adiposity, the sensitivity and specificity of BMI in detecting true excess adiposity can be problematic for people with borderline obesity (around 30 kgm2) and can only be a certainty at higher BMIs. However, the relationship between adiposity and health is more nuanced, even among those with obesity. Whilst higher adiposity is associated with increased cardiometabolic risk (insulin resistance, dyslipidaemia, and other cardiovascular risk factors), fat distribution is important. Central adiposity is more strongly associated with markers of cardiometabolic risk, but it is specifically intrabdominal, or visceral adipose tissue (VAT), that is a far stronger predictor. Yet even VAT may not infer the true risk, as it is ectopic fat (e.g. in liver, muscle, heart and pancreas) that represents a true mechanistic issue.
“It is obviously unfeasible to routinely diagnose obesity using reliable measures of adiposity, as described. Therefore it is key that measures of body weight/obesity be coupled to health markers as well, as described in this paper. Not forgetting the last category in relation to metabolic organs — given that impaired glucose tolerance, prediabetes, and cardiovascular disease are the most common health consequences of obesity – if we wish to truly define risk, including those with “pre-clinical” obesity. This will better triage individuals for intervention through weight loss (e.g. with weight loss drugs that are costly and in scarce supply) or other diet and lifestyle modifications.
“However, it is also important to note that focusing solely on BMI as a marker of health, even with this suggested differential diagnosis, does miss other individuals who may be at risk despite a normal BMI. Those who can be described as “metabolically obese”, and who exhibit similar or greater metabolic risk than those who are obese. This may represent up to 1 in 10 “lean” individuals who would otherwise go undetected. Emphasising the need for more routine measures of risk, than simply BMI, to identify individuals at risk.”
Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:
“This report contains an important set of recommendations that define the clinical syndrome of obesity and differentiates it from an excess accumulation of body fat in the presence of normal bodily function (pre-obesity).
“The report is based on a Delphi review where consistency of agreement on views for the treatment of obesity is sought from experts. In most cases the agreement was 100 percent and in a few cases 95 percent.
“Body mass index (BMI) is currently used to define obesity and while it is useful for looking at groups of people it can be misleading in the range of BMI 25-34.9. For example, there are a few individuals who are muscle bound and have low levels of body fat but have a BMI in the range 30-35. BMI has been useful for tracking the increase in obesity in populations: the proportion of adults with a BMI greater than 30 has increased from around 15% in the 1991 to about 26% now. But now a far higher proportion those classified as obese are severely obese with multiple health problems. These recommendations suggest the use of other measure beside BMI to characterise clinical obesity.
“In conclusion, the recommendations are helpful because they will help target interventions to those that need them most. The recognition of clinical obesity as disease would hopefully persuade lawmakers to regard it as a disability. This would have implications in terms of discrimination particularly in employment as well as the social stigma associated with the condition.”
Comments from the pilot SMC for Ireland:
Dr Alexandra Cremona, Associate Professor of Human Nutrition and Dietetics, University of Limerick, said:
“This study is significant because it redefines obesity as a complex, chronic systemic illness, moving beyond the limitations of a BMI-centric model to focus on the functional impairments and health impacts caused by excess adiposity. By introducing the concepts of “preclinical” and “clinical” obesity, it enhances diagnostic precision, enabling individualized care that considers both risk and active disease states. This reframing also addresses weight stigma by emphasizing the biological and systemic factors underlying obesity, rather than attributing it solely to personal choices, thus promoting equitable healthcare access. Moreover, the study provides a clear distinction between health and illness in obesity, offering actionable pathways for healthcare policy, early intervention strategies, and targeted research into disease mechanisms. If adopted, this innovative framework has the potential to refine current models of obesity care, improve patient outcomes, and shift public health approaches, making it a pivotal contribution to the field.
“The study’s strengths lie in its global expertise, with contributions from 58 international experts and endorsements from 76 organizations, ensuring its applicability across diverse populations. Its comprehensive framework moves beyond BMI, integrating direct fat measurement (e.g., DEXA scans), anthropometric criteria (e.g., waist circumference, waist-to-hip ratio), and functional assessments (e.g., organ dysfunction and limitations in daily activities) to enhance diagnostic precision. By focusing on organ dysfunction and quality of life, it highlights the real-world impact of obesity, making the recommendations clinically relevant. The rigorous Delphi consensus methodology ensures evidence-based, well-validated findings, while the inclusion of individuals with lived experience adds an empathetic, patient-centred perspective. These features together mark a significant step forward in advancing obesity care.
“Certain limitations warrant attention: implementing advanced diagnostic methods like DEXA scans may be resource-intensive, particularly in low-resource settings. The study also lacks longitudinal data on outcomes and cost-effectiveness, which are essential for assessing the impact of its recommendations in real-world contexts. Additionally, the distinction between “preclinical” and “clinical” obesity may complicate practical diagnosis, especially for general practitioners. While the criteria emphasize physical health impacts, mental health aspects of obesity may be underrepresented, limiting a holistic understanding of the condition. As with any newly published recommendations, challenges may be faced in integration and adoption into existing systems. However, these limitations are not insurmountable and can be addressed through further research to evaluate outcomes, refine criteria, and develop scalable solutions tailored to diverse healthcare settings.
“The findings are robust and innovative, marking a potential paradigm shift in obesity care. The distinction between preclinical and clinical obesity is particularly valuable as it acknowledges the spectrum of obesity-related health impacts, from risk factors to manifest disease. The emphasis on functional impairments rather than solely body size aligns more closely with patients’ lived experiences and the complexities of chronic diseases.
“The integration of the Lancet Commission’s framework into Ireland’s recently adapted obesity guidelines offers an opportunity to enhance and elevate the current approach. By refining diagnostic criteria and emphasizing the distinction between preclinical and clinical obesity, this framework could bring greater precision to care and prevention strategies. However, successful implementation will require further research to bridge gaps and adapt the recommendations to Ireland’s specific context. The framework’s focus on reducing weight bias and stigma is particularly commendable, aligning with the need to remove barriers to effective obesity management and foster equitable healthcare practices.
“The Lancet Commission’s redefinition of obesity as “preclinical” and “clinical” closely parallels the Edmonton Obesity Staging System (EOSS), particularly its staging of obesity as progressing from minimal risk (Stage 0 and 1) to more severe health impacts (Stages 2–4). However, the Lancet framework attempts to differentiate itself by explicitly framing “preclinical obesity” as a risk state (excess adiposity with preserved organ function) and “clinical obesity” as a distinct chronic disease characterized by organ dysfunction or significant functional limitations. While this distinction may seem similar to EOSS’s progression of stages, the Lancet places stronger emphasis on recognizing obesity as an independent disease entity rather than solely a risk factor for comorbidities. This reframing offers potential to influence public health policies and clinical approaches by shifting focus to diagnosing and managing obesity itself, irrespective of associated conditions. Nonetheless, the practical differences between the two frameworks may feel minimal, and whether this redefinition significantly advances clinical care will depend on its implementation and adoption.”
Dr Laura McGowan, Senior Lecturer in Nutrition and Behaviour Change, Queen’s University Belfast, said:
“This Lancet Commission represents an important step forward in the field of obesity and the care for those living with obesity.
“It advances scientific agreement across a broad range of experts on what constitutes clinical obesity, and how we can consider this as a clinical condition in its own right, and more than just a risk factor for other conditions, like type 2 diabetes and cardiovascular disease.
“The research is robust in its methods and a strength is that it included the views and opinions of those living with obesity.
“It is particularly relevant for those living in Northern Ireland, as at present, patients here don’t have access to NHS-supported specialist obesity management services, including new wave medications like the GLP-1’s and bariatric surgery. Defining clinical obesity and making the diagnostic criteria clear may help this to become better resourced within the NHS in NI, which is urgently needed.”
Comments from the New Zealand SMC:
Professor Lisa Te Morenga (Ngāpuhi, Ngāti Whātua Ōrakei, Te Uri o Hau, Te Rarawa), Professor of Māori Health and Nutrition and Rutherford Discovery Fellow, said:
“One third of New Zealand adults have a BMI of 30 or more classifying them as obese. BMI is calculated from two easy to measure variables: height and weight. On average having a high body weight relative to height is an indicator of having excess body fat and increased risk of some diseases. Its simplicity makes it a useful, affordable tool to assess health and disease risk in large population studies For example, it allows us to monitor changes in the health risk status of the population in relation to changes in factors such as the quality of the food supply, changing patterns of physical activity, or environmental pollutants.
“However, BMI was never intended to diagnose excess body fatness and risk of disease of an individual. Someone with a high weight relative to their height giving them a BMI of 30 might have lots of muscle, or carry lots of fat on their bum and thighs, neither of which confer much risk of illness. On the other hand some groups in our population (notably people of Asian and Indian descent) can carry a small amount of excess fat in high-risk places (around the vital organs) while presenting with a relatively low BMI, and therefore their increased risk of conditions such as diabetes could be missed.
“So it is a welcome advance to have this report recommending a more nuanced approach to diagnosing and supporting individuals with obesity that either puts them at increased risk of illness (pre-clinical obesity) or is present with illness (clinical obesity). The focus on obesity as a disease as opposed to a lifestyle choice is well overdue and will contribute to reducing the weight stigma experienced by people with obesity, particularly Māori and Pacific peoples. It will also enable medical professionals to be more targeted in the type of treatment delivered to these patients (i.e. needs-based treatment) thus reducing pressure on our healthcare system.”
No conflicts of interest declared.
Professor Sir Collin Tukuitonga, Professor of Public Health, University of Auckland, said:
“The Body Mass Index (BMI) is widely used as a measure of obesity globally, even though the index is an unreliable measure of body fat.
“Alternative measures, such as bioimpedance body fat measures, are impractical for clinical use.
“Several studies have shown that Polynesian people have more muscle mass than fat and cut off points have been adjusted to take account of this reality.
“Overweight and obesity are very common in Pacific Islands people and nine of the 10 nations in the Pacific are among the most obese nations on Earth. Obesity is a key driver of high rates of Type 2 Diabetes Mellitus (T2DM) in the Pacific.
“The new guidelines will improve care for people with obesity by better differentiation on obesity categories – pre-clinical obesity (minimal health risk) and clinical obesity with significant risk of complications.
“The change will help with reducing stigma and improve patient management.”
No conflicts of interest declared.
Professor Rinki Murphy, Department of Medicine, University of Auckland; endocrinologist and clinical head of Specialist Weight Management Service, Te Mana Ki Tua, Counties Health NZ, said:
“In the context of the longstanding debate over whether obesity is a disease or simply a risk factor for other diseases, the new definition of what constitutes clinical obesity as a disease, helps clarify this situation.
“The recommendation is to use both BMI and body fat percentage or waist circumference, (unless the BMI is clearly very high, greater than 40), and then to screen for obesity-induced organ dysfunction or loss of functional ability for conducting activities of daily living.
“This information is routinely collected by those specialising in obesity management, but this has not been used for distinguishing those with clinical obesity as a disease versus those who have pre-clinical obesity with no significant impairment. This distinction is more helpful in providing personalised health advice than the historic grading of obesity by the level of high BMI (class 1, 2, 3 etc).
“An important goal of these recommendations is to enhance access to comprehensive care and evidence-based treatments for people living with clinical obesity and to reduce weight-based bias and stigma. Currently, people receiving the extremely limited number of public-funded bariatric surgeries in New Zealand already need to fulfill the criteria for clinical obesity, and they must meet additional rationing criteria based on the severity, number and type of organs affected.
“There is currently no national public funding for any obesity medication, but perhaps defining clinical obesity as a disease entity will improve access to more effective, obesity treatment options.”
Conflict of interest statement: “Clinical head of Specialist weight management service, Te Mana Ki Tua, Counties Health NZ, Te Whatu Ora; Endocrinologist, Auckland Diabetes Centre, Te Toka Tumai, Auckland Health NZ, Te Whatu Ora; Pharmac diabetes advisory committee member; Speaking honoraria from Lilly, Novo Nordisk, Boeringer Ingelheim; Consultancy for NZ Clinical Trials”
Boyd Swinburn, Professor of Population Nutrition and Global Health, University of Auckland, said:
“The 58 international experts involved in this Commission (importantly including people with lived experience of obesity) have done a superb job of thinking through and answering many of the really challenging questions around obesity – for example: how should Body Mass Index (BMI) be used; is obesity a disease or an illness or a risk factor for disease; when should people with obesity be considered for treatment; how to deal with weight bias and stigma?
“The Commission recommends that BMI is valuable for epidemiological studies and clinically as a screening tool. Beyond that, other measurements (such as waist and hip circumference) and assessments of organ function (such as liver, kidney, heart) are needed to be able to classify people as having obesity or not and, within the obesity group, into pre-clinical or clinical obesity depending on whether there is evidence of organ dysfunction or not. People with a very high BMI (greater than 40) are considered to have clinical obesity.
“The conversion of a continuous, imperfect single measure of BMI into a more nuanced ‘syndrome-approach’ to define more sensitive and specific categories of obesity will be great use for clinicians in deciding who to treat and for healthcare policymakers in deciding eligibility for state-funded treatment, including medications and surgery.”
No conflicts of interest.
Professor Sir Jim Mann, Professor in Medicine, Co-Director Edgar Diabetes and Obesity Research Centre, said:
“The Lancet Diabetes and Endocrinology Commission report on the ‘Definition and diagnostic criteria of clinical obesity’ has made a series of recommendations. Some are helpful in that they categorically confirm what those of us who research and practice in this field have long been saying in response to the continuing debate concerning the value of body mass index (BMI) as a measure of obesity. BMI is a useful measure of health risk at a population level and for epidemiological studies.
“However, when BMI is used as an individual measure of health, the consequences of excess adiposity should be considered in terms of total body fatness as measured, for example, by a DEXA scan or by considering the distribution of the excess fat around the body. Given that it is not feasible to undertake scans on everyone with a high BMI, in practice this means measuring waist circumference, waist-to-hip ratio or waist-to-height ratio.
“It is also good to see emphasis on the need for all people living with obesity to receive appropriate personalised health advice free of bias and stigma, which are obstacles to prevent and treat obesity.
“Likely to be more contentious is the suggestion that, despite the relationship between increasing levels of excess body fat and ill health being a continuum, there is a need to define ‘health’ and ‘ill-health’ as distinct entities. The Commission therefore suggests distinguishing ‘clinical obesity’ from ‘pre-obesity’, the former being characterized by signs and symptoms of altered organ function or inability to carry out daily activities as a result of excess body fat.
“Although the Commissioners provide cogent arguments for this approach and suggest reasonable management approaches for the two entities, as well as public health approaches to prevention, it could be argued that given the continuum of risk, the relatively arbitrary nature of BMI cut offs, and the contribution of several risk factors to health outcomes, this is not the most appropriate approach for the calculation of attributable risk to individuals or indeed to managing the epidemic proportions of obesity.
“I would also be concerned that in countries such as ours where there is considerable pressure on health budgets that the bulk of funding available for the management of obesity would be devoted to the treatment of those with ‘clinical obesity’ whereas there is much to be gained from the perspective of individuals as well as public health by intensive management of many of those in the ‘pre-obesity’ category, e.g. those with pre-diabetes. While such benefit is acknowledged in the report there is emphasis on the needs of those who are defined as clinically obese and very likely that limited funding will be directed to that group.
“Despite these reservations, I believe this to be an important document that deserves widespread discussion and indeed implementation of a national plan of action for obesity alongside the national action plan of action for diabetes, type 2 being one of the most important consequences of obesity, currently under consideration of the Government of Aotearoa.”
No conflicts of interest.
Dr Wayne Cutfield, Professor of Paediatric Endocrinology, Liggins Institute, University of Auckland; and Starship Children’s Hospital, said:
“The comprehensive Lancet Commission article highlights two issues:
“GPs and, increasingly the general populace, use and increasingly understand BMI as a measure of adiposity. Waist circumference requires age, gender and ethnicity determined normal values and cutoffs. In New Zealand, these do not exist and would require more intricate assessment of adiposity. Yes, it would add precision, but would be more difficult to use and interpret. BMI is imperfect but is an easy tool to use and understand and usually identifies those who are overweight or obese.
“The pre-clinical obesity classification implies that this group has less of a problem that requires less management. However, the Commission doesn’t acknowledge that obesity leading to diabetes, hypertension, heart disease or cancer takes many years if not decades to develop. An individual with pre-clinical diabetes who loses weight will be further away from developing these diseases, which is a good thing.”
No conflicts of interest.
‘Definition and diagnostic criteria of clinical obesity’ by Francesco Rubino et al. was published in the Lancet Diabetes & Endocrinology at 23:30 UK time on Tuesday 14 January 2025.
DOI: 10.1016/S2213-8587(24)00316-4
Declared interests
Dr Adam Collins: “No conflict of interest.”
Prof Tom Sanders: “Member of the Science Committee British Nutrition Foundation. Honorary Nutritional Director HEART UK.
Before my retirement from King’s College London in 2014, I acted as a consultant to many companies and organisations involved in the manufacture of what are now designated ultraprocessed foods.
I used to be a consultant to the Breakfast Cereals Advisory Board of the Food and Drink Federation.
I used to be a consultant for aspartame more than a decade ago.
When I was doing research at King’ College London, the following applied: Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks. In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011. This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London. The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar. Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.”
For all other experts, no reply to our request for DOIs was received.