Global obesity figures miss out more than half a billion: study

Though official estimates say there are 600 million obese adults in the world, a new study claims that this estimate misses out more than half a billion fat people.

The study warns that by ignoring the nuances, researchers underestimate adult obesity levels by over 400-500 million.

Associate professors Daniel Hruschka of Arizona State University's School of Human Evolution and Social Change and Craig Hadley of Emory University's Department of Anthropology are developing more accurate tools by taking a closer look at the different ways that people's bodies are built in different places around the world.

Body Mass Index (BMI), a simple ratio of weight to height, is a standard front-line tool for assessing body fat and for identifying people who are at greater risk of fat-linked diseases, like diabetes and cardiovascular disease.

But, since BMI relies only on height and weight, it can mistake people who are naturally stocky and muscular as overweight. On the flip side, naturally slender individuals may be able to pack on a great deal of body fat before standard BMI cutoffs identify these slender individuals as overweight or obese.

Organisations in some countries, such as Japan and China, have begun to propose modified cutoffs for assessing obesity and obesity-linked risk that are more appropriate for more slender body builds often found in East Asia.

However, there is still no clear consensus how to adjust BMI cutoffs to deal with these population differences worldwide.

The researchers' proposed solution to these biases relies on the idea of "basal slenderness." This is the expected BMI in a population before it begins to add excess fat due to urbanisation, increasing opportunities for consumption of high-calorie foods and other changes due to modernisation.

Adjusting BMI for a population's basal slenderness gives each population a cutoff that reflects the amount of a person's BMI that is due to body fat versus other body tissues.

This study has been published in Obesity Reviews.