New global definition changes how childhood obesity is identified

A new global definition of clinical obesity classifies far fewer children as obese than the widely used body mass index (BMI), according to a large international study. And the findings could lead to changes to how childhood obesity is identified and managed.

The research, led by Murdoch Children's Research Institute (MCRI), involving 786,557 participants from Australia, Canada, Estonia, Finland, the Netherlands, the UK and the US is the first to examine the prevalence of clinical obesity from early childhood through to older age.

Published in eClinicalMedicine, it found while clinical obesity was less prevalent than BMI-defined obesity during childhood and early adulthood, it became increasingly common with age, affecting more than half of adults aged 65 to 74 years.

The study evaluated the new Lancet Commission definition of clinical obesity, which goes beyond BMI, a measure of weight relative to height, and considers whether excess body fat is accompanied by symptoms of obesity-related health problems or limitations in daily activities.

The research discovered clinical obesity affected only 2.1 to 4.9 per cent of children and adolescents, compared with 7 to 10.8 per cent classified as obese using BMI criteria. But the prevalence of clinical obesity rose throughout adulthood, surpassing BMI-defined obesity from age 55-64 years onwards and peaking at 52 per cent among adults aged 65-74 years. Clinical obesity was also higher among men during early-to-mid adulthood while women experienced higher rates later in life.

MCRI Inflammatory Origins Group Dr Danielle Longmore said the findings showed that while BMI was useful for looking at obesity across entire countries, it failed to capture the full picture of a person's overall health.

She said the new Lancet definition would help clinicians make more informed decisions around when to intervene and how to manage obesity.

"The distinction could have implications for how obesity is assessed and treated, including decisions about weight-loss medications and dietary recommendations," Dr Longmore said.

"It could also help researchers and clinicians better understand the healthcare needs associated with obesity at different stages of life, with implications for planning and resourcing.

"This definition is a starting point for looking at obesity in a way that better reflects what healthcare professionals are already seeing in practice. People can have a similar BMI but develop very different health outcomes related to excess body fat."

Understanding which children are already showing signs of obesity-related health complications will help inform future prevention and treatment strategies. Childhood and adolescence are a critical window for reducing long term poor health outcomes related to obesity such as heart diseases, type 2 diabetes, hypertension, stroke and certain cancers."

Professor David Burgner, MCRI Inflammatory Origins Group Leader 

But Professor Burgner cautioned given none of the cohort data included complete information on all diagnostic criteria under the Lancet definition, future longitudinal studies were needed to determine the true prevalence of clinical obesity.

The data was sourced from the Avon Longitudinal Study of Parents and Children (ALSPAC), the Barwon Infant Study, Child Health CheckPoint, the Canadian Healthy Infant Longitudinal Development study, the Estonian Biobank, Generation R, the Northern Finland Birth Cohorts, the National Health and Nutrition Examination Survey, the Physical Activity and Nutrition in Children study, UK BioBank and the Cardiovascular Risk in Young Finns Study.

Researchers from University of Toronto, Erasmus University, University of Eastern Finland, University of Turku, University of Oulu, University of Tartu, the University of Melbourne, University of Otago, Kuopio University, Finnish Cardiovascular Research Center, Fimlab Laboratories, Tampere University McMaster University, Deakin University, Barwon Health and The University of Sydney also contributed to the research.