International experts have warned that up to 60 per cent more adults could be classified as obese following a proposed radical shake-up of the body-mass-index (BMI) system. Currently, a BMI between 18.5 and 25 is considered healthy, 25 to 29 is overweight, and 30 or above denotes obesity, where the risk of serious illness escalates. However, 58 international specialists have advocated for an overhaul of this diagnosis, arguing that BMI alone is an insufficient tool for assessing unhealthy body fat.

The proposed new definition suggests incorporating additional measures such as waist size and weight-to-height ratio to provide a more comprehensive picture. Under these revised rules, obesity would be defined as a BMI above 30 combined with at least one raised anthropometric measure (like increased waist circumference or waist-to-height ratio), or simply a BMI over 40. Furthermore, individuals with a BMI below 30 could still be deemed obese if they exhibit at least two raised anthropometric measures, a category researchers have termed 'anthropometric-only obesity'.

Researchers from Harvard University and Massachusetts General Hospital, analyzing data from over 300,000 American adults, discovered that adopting this new definition would increase the number of people classified as obese by almost 60 per cent. This surge was primarily driven by the inclusion of individuals falling under 'anthropometric-only obesity'. These individuals, despite having what appeared to be a healthy BMI, were found to have a significantly higher risk of organ dysfunction and diabetes, and were more than three times as likely to suffer organ damage. In the US study, 206,361 adults met the new criteria, with a mere 0.2 per cent of previously obese individuals no longer qualifying due to normal other measures.

The implications of such a change are substantial. In Britain, for instance, where approximately 13 million adults are currently obese, the new calculation could see this figure soar to nearly 21 million. Experts have labeled these findings 'important', warning that a 'substantial rise in obesity prevalence' would carry 'profound financial and public-health implications'. The study also revealed that nearly 80 per cent of participants aged 70 or over would be classified as obese under the new criteria, effectively doubling the current rate for this age group.

The push for this reform, first proposed in January by the 58 global experts in a report published in the prestigious Lancet Diabetes & Endocrinology journal, stems from the belief that BMI alone is not a 'nuanced' enough measure. Their recommendations have garnered endorsement from various organizations, including the Royal College of Physicians.

This re-evaluation of obesity definitions comes amidst a series of new anti-obesity measures recently implemented in England. Under new Government laws, practices such as 'buy one, get one free' deals on sweets, crisps, sugary drinks, and other snacks have been outlawed, alongside free refills of fizzy drinks in restaurants and cafés. Further crackdowns are anticipated in January with a ban on online advertisements for unhealthy food and drink, and restrictions on TV advertising before 9 pm. These policies are designed by ministers to combat Britain’s escalating obesity crisis, which was linked in a sobering report last year to a 39 per cent rise in type 2 diabetes among under-40s, affecting around 168,000 young adults. Excess weight is also a significant factor, linked to at least 13 types of cancer and identified as the second-biggest preventable cause of the disease in the UK by Cancer Research UK.