New diagnostic criteria for obesity

International experts have called for a major overhaul of the way obesity is diagnosed, to go beyond BMI to define when obesity is a disease.

Current medical approaches to diagnosing obesity rely on BMI, which is not a reliable measure of health or illness at the individual level. This can result in misdiagnosis with negative consequences for people living with obesity.

A global Commission on Clinical Obesity, published in The Lancet Diabetes & Endocrinology recommends including measures of body fat – e.g., waist circumference or direct fat measurement, and objective signs and symptoms of ill health.

The authors introduce two new diagnostic categories of obesity based on objective measures of illness:

• Clinical obesity (a chronic disease associated with ongoing organ dysfunction due to obesity alone), and
• Pre-clinical obesity (associated with a variable level of health risk, but no ongoing illness).

The proposal is designed to address current limitations in practice and healthcare policies, which may prevent individuals with obesity from getting the care they need.

The following methods can be used to confirm excess fat mass:

• At least one measurement of body size (waist circumference, waist-to-hip ratio or waist-to-height ratio) in addition to BMI
• At least two measurements of body size (waist circumference, waist-to-hip ratio or waist-to-height ratio) regardless of BMI
• Direct body fat measurement (such as by a bone densitometry scan) regardless of BMI
• In people with very high BMI (e.g. >40 Kg/m2) excess body fat can be assumed.

Criteria for clinical obesity include:

• Breathlessness caused by effects of obesity on the lungs
• Obesity-induced heart failure
• Knee or hip pain, with joint stiffness and reduced range of motion as a direct effect of excess body fat on the joints
• Changes in bones and joints in children and adolescents limiting movement

• See Advanced Practice – Obesity management in primary care

Rubino F, et al. Lancet Diab Endocrinol; January 2025. https://www.thelancet.com/commissions/clinical-obesity