By 2035 over 4 million adults will be morbidly obese across England, Wales, and Scotland

The highest prevalence rates will be seen in Wales, with around 13% of Welsh men and 9% of Welsh women likely to be morbidly obese by 2035 if current trends continue. The prevalence of morbid obesity is expected to vary widely between the three countries and in different age groups. By 2035, 16% of English men aged 55-64 are likely to be morbidly obese. That compares to 0% of Scottish men aged 15-24 (see table).

The authors warn that the study presents a disturbing picture of substantial rises in morbid obesity rates that will have huge health and financial implications for health services and society. They call for concerted action by individuals and governments to reverse this trend.

The prevalence of morbid obesity is increasing worldwide, with numbers doubling in the past 20 years. A recent global study reported morbid obesity levels ranging from less than 0·1% in Chinese women to 23·1% in American women.

Morbid obesity entails far more serious health consequences than moderate obesity and is associated with a higher risk of chronic diseases such as type 2 diabetes, heart disease, stroke, mental illness, and some cancers.

Morbid obesity is already a huge burden on the economy and health services, accounting for around a third of all obesity-related costs.

While overweight and obesity trends for England, Wales, and Scotland have been projected to 2035, until now, no trend estimates existed for morbid obesity.

In this study, Laura Keaver from the CRISP research group at the Institute of Technology, Sligo, Ireland and Dr Laura Webber from the UK Health Forum, London used height and weight data from the Health Survey for England, Welsh Health Survey, and the Scottish Health Survey (2004-14) for adults aged 15 and older (in 5 year age groups) to create a model predicting BMI trends (healthy weight, overweight, obesity, and morbid obesity) over the next 17 years.

The new estimates indicate that rates of morbid obesity in adults will reach 5% in Scotland (compared to 4% in 2015), 8% in England (2.9% in 2016), and 11% in Wales (3% in 2015) by 2035 (see table 1).

According to the authors: "Our study reveals a worrying picture of rising morbid obesity across England, Wales, and Scotland that is likely to weigh heavily on healthcare systems and economies. Strong measures to reverse this future trend must be an important public health priority."

In further analyses, the research team predicted future trends in social inequalities in obesity (BMI of 30kg/m² or over) by modelling BMI data from the health surveys to project trends in adult obesity prevalence (aged 16 or older) according to their sex and social group (occupation and education).

Previous studies have found that lower socioeconomic position is linked with higher adult BMI, and socioeconomic inequalities in obesity are increasing in many European countries. But whether these associations will change over the coming decades is unclear.

By 2035, obesity rates will be highest, and see the greatest rise, in adults working in routine and manual positions. As a result, the difference in obesity levels between those in managerial roles (29% males, 31% females) and those in routine and manual roles (39% males, 40% females) is expected to widen in England and Wales (with the exception of English females where it is expected to reduce; table 2).

In contrast, the gap in obesity levels between those with less than tertiary education (i.e., university or trade school/college) and those with tertiary education is projected to close in all countries with the exception of Welsh females where it is projected to increase (table 3).

The authors conclude: "Our findings highlight that future interventions to tackle obesity must be accessible to everyone and should be designed to impact all sectors of society to further reduce these inequalities."

The authors point out the limitations that apply to the quality, precision, and availability of the data demand cautious interpretation (e.g., weight and height was self-reported in Wales and measured in England and Scotland). They also note that uncertainties always exist when making predictions as past trends do not always predict future trends. In addition, the study cannot predict the effect that future interventions or policies will have on social inequalities in obesity.