Definition and diagnostic criteria of clinical obesity

Abstract

Section snippets

Executive summary

Current BMI-based measures of obesity can both underestimate and overestimate adiposity and provide inadequate information about health at the individual level, which undermines medically-sound approaches to health care and policy. This Commission sought to define clinical obesity as a condition of illness that, akin to the notion of chronic disease in other medical specialties, directly results from the effect of excess adiposity on the function of organs and tissues. The specific aim of the

Conception of the Commission

The idea and general plan to convene a global expert group for the definition of diagnostic criteria of chronic illness in obesity (clinical obesity) was conceived by FR, and discussed with editors of The Lancet Diabetes & Endocrinology journal for consideration as a Lancet Commission. The Commission on clinical obesity was organised in partnership with the Institute of Diabetes, Endocrinology and Obesity at Kings Health Partners. Additional scientific input about the programme of the

General principles

Although the notion of disease might seem obvious, a clear definition of disease does not exist. One comprehensive approach to the definition of disease was proposed by Stanley Heshka and David Allison:²⁷ (A) a condition of the body, its parts, organs, or systems, or an alteration thereof; (B) resulting from infection, parasites, nutritional, dietary, environmental, genetic, or other causes; (C) having a characteristic, identifiable, marked group of symptoms or signs; and (D) deviation from

Commissioners' views on obesity as a disease

The idea of obesity as a disease was a controversial subject also within this Commission. Initial opinions diverged substantially, clearly indicating that a consensus would not be reached on a blanket definition of obesity as a disease, at least as currently defined. A specific pre-Delphi survey on the question of whether obesity is a disease showed that more than half of the commissioners rejected the all-or-nothing scenario implied in the question, but supported the view that obesity is a

Conceptual and practical issues in the current definition of obesity

Obesity is currently conceived and defined as a condition of excess adiposity that presents a “risk to health”.³⁴ The current diagnosis of obesity worldwide is based on BMI, calculated as weight in kilograms divided by height in metres squared. According to WHO, an adult with a BMI of 30 kg/m² or higher is considered to have obesity.This definition has been widely adopted and used in epidemiological studies, clinical practice, and public health policy.³⁵ However, several studies have shown that

Views and attitudes about obesity among patients, health-care professionals, and policy makers

The debate around the idea of obesity as a disease elicits polarising and often emotional reactions, often based on non-medical considerations.Those who support the idea often cite the fact that such a move would minimise weight-based stigma and discrimination, as it shifts focus away from blaming the individual. This outcome is plausible and indeed desirable, but is arguably not a reason why a medical condition should be considered a disease. Critics of the idea are concerned that defining

Reframing obesity and its clinical characterisation

Obesity can increase risk for other illnesses and premature mortality, induce illness on its own, or both. A better aetiological, pathophysiological, and clinical characterisation of obesity is therefore warranted.

Anthropometric versus clinical model

Although alternative anthropometric measures and biomarkers have been suggested as possible replacements for BMI as diagnostic tools or to inform decisions about treatment, they have not been used as a measure of health in individual patients and would have insufficient diagnostic accuracy as a measure of ongoing illness.The diagnosis of disease in other areas of medicine is generally based on the detection of signs and symptoms induced by dysfunction of organs or the whole organism (see

Causes of obesity

The causes of obesity are multifactorial and incompletely understood.2, 5, 80 Genetic, environmental, psychological, nutritional, and metabolic factors can induce alterations of the biological mechanisms that maintain normal mass, distribution, and function of adipose tissue, thus contributing to obesity. The accrual of body fat occurs as a function of positive energy balance, whereby the rate of appearance of macronutrients exceeds that of disappearance. Although often attributed to overeating

Clinical manifestations of organ dysfunction directly caused by obesity in adults

Obesity can directly cause organ dysfunction via several pathophysiological mechanisms, including the physical effect of increased adipose tissue mass, the presence of ectopic fat within tissues and organs, metabolic effects, inflammatory mechanisms, and psychological consequences (figure 3). The development of organ dysfunction and obesity complications, whether cardiometabolic or biomechanical, can arise at different levels of adiposity in different individuals. Moreover, the severity of

Obesity in children and adolescents

Child and adolescent obesity has become a major health, societal, and economic burden worldwide.¹⁴⁷ Among children and adolescents aged 5–19 years, the prevalence of overweight and obesity has risen substantially, from just 4% in 1975 to more than 18% in 2016. In this age group, the worldwide prevalence of obesity increased from 1% in 1975 to 7% (6% of girls, 8% of boys) in 2016, with more than 124 million children and adolescents having the disease. Obesity can develop early in life: in 2019,

Clinical manifestations of organ dysfunction directly caused by obesity in children and adolescents

This section reviews key manifestations of clinical obesity in children and adolescents, describing how excess adiposity affects major organs, tissues, and body systems to cause ill health. As in adults, however, obesity can also facilitate development of obesity-related diseases or disorders that increase risk of morbidity, mortality, and impaired quality of life in childhood, and in adulthood if obesity remains untreated.

Commission recommendations: definitions and diagnostic criteria of clinical obesity

The conclusions and recommendations of this Commission were reached through extensive discussion of evidence and viewpoints, plus a formal consensus development process to generate recommendations backed by the strongest majority within the expert group. All definitions, recommendations, and diagnostic criteria were agreed by either unanimous or near-unanimous level of consensus within the expert group. All consensus-based conclusions and recommendations, each with its related grade of

Strengths and limitations of this Commission

We acknowledge several limitations in the work of this Commission.A Delphi-like method was used to achieve shared conclusions among commissioners. The iteration characteristics of the Delphi technique have intrinsic limitations and might lead to groupthink, where participants might conform to dominant opinions of the group, which could affect objectivity.¹⁹⁷ However, the extensive use of live and offline pre-Delphi surveys, and discussions within smaller subgroups (subcommittees), provided

Conclusion

The idea of obesity as a disease is at the centre of one of the most controversial and polarising debates in modern medicine, with broad and far-reaching implications for people affected and the society as a whole.Consistent with its original definition as a “condition that poses a risk to health”,⁴ obesity has been framed and extensively studied as a harbinger of other diseases. The manifestations of obesity as an illness, however, have not been adequately characterised. Such lack of clinical

Declaration of interests

FR declares research grants from Ethicon (Johnson & Johnson), Novo Nordisk, and Medtronic; consulting fees from Morphic Medical; speaking honoraria from Medtronic, Ethicon, Novo Nordisk, Eli Lilly, and Amgen; has served (unpaid) as a member of the scientific advisory board for Keyron, and a member of data safety and monitoring board for GI Metabolic Solutions; is president of the Metabolic Health Institute (non-profit); and is sole director of Metabolic Health International and London Metabolic

Acknowledgments

The Lancet Diabetes & Endocrinology Commission on Clinical Obesity was organised in partnership with by the Institute of Diabetes, Endocrinology and Obesity at King's Health Partners. King's Health Partners provided logistic and administrative support for organisation of online meetings, internal communication and the consensus development process. We would like to acknowledge the invaluable support of the Institute of Diabetes, Endocrinology and Obesity at King's Health Partners. In