Obesity prevalence would shift significantly under proposed new criteria

In the first multinational study of a proposed change to how obesity is defined - which calls for health factors beyond a person's height and weight to be considered - an international team of researchers found the prevalence of obesity would drop significantly, highlighting concerns that the new criteria could hinder the prevention and early detection of serious health conditions.

The study, was authored by researchers from Emory University and Johns Hopkins University in the US, University of Queensland in Australia, Zhejiang University School of Medicine in China and Universidad Peruana Cayetano Heredia and Universidad Científica del Sur in Peru. It analysed data from 56 countries to compare the prevalence of pre-clinical and clinical obesity using the existing BMI criteria with what the prevalence would be under the proposed criteria that requires at least one health condition to already be present before a person is considered clinically obese, such as diabetes, hypertension or high cholesterol.

"Obesity is a serious problem and the definitions we use have implications for clinical treatment, health expenditures, disease surveillance, and for people's awareness of their own health risks,” said the study's lead author, Dr Rodrigo M Carrillo-Larco, assistant professor of global health at Emory University's Rollins School of Public Health. “So, it is important to understand how much any new definition would impact the prevalence of obesity.”

When the additional health issues were included into the criteria for obesity, the prevalence dropped significantly among the 142,250 adults surveyed - with some nations seeing a drop of more than 50% - but the results varied by nation and gender. For example, the East African nation of Malawi had among the highest decreases in obesity prevalence under the proposed definition, but the decline was uneven among men (68%) and women (53%).

While the new definition could be more aligned with current disease risk, the researchers urged caution before considering a shift in obesity surveillance to the proposed standard because doing so would create substantial challenges in terms of measurement, equity, and implementation. And for individuals who would no longer be considered obese, it could provide a dangerous false sense of security.

"At the population level we would expect the prevalence of obesity to drop, but we should be mindful that it's an artificial drop because the new definition is more strict or complex - that reduction in obesity is not real," added Carrillo-Larco. "If we're going to use the definition at some point, we need to remember that doesn't mean preventing obesity and the associated comorbidities are not important. Just because people who have high BMI but no additional comorbidities would not be considered clinically obese, it does not mean that by some miracle their risk has reduced. They should still receive preventive care counselling, they should still be eating healthy diets, and they should continue working to achieve their optimal healthy weight."

The findings were reported in the paper, ‘Prevalence of pre-clinical and clinical obesity in adults: Pooled analysis of 56 population-based national health surveys’, published in PLOS Global Public Health. To access this paper, please click here