People with severe obesity (body mass index [BMI] of 40 or higher) are now considered at risk of developing serious outcomes from coronavirus disease 2019 (Covid-19) by the Centers for Disease Control and Prevention. With novel coronavirus now spread across 187 countries with 2.4 million cases worldwide, the importance of understanding the population at risk is ever-increasing. Severe obesity as a risk factor for Covid-19 emphasises that the implications of this disease are not limited to older age groups and that countries with high numbers of severely obese patients may experience increased pressure on their health systems.

Studies from previous viral pandemics, such as the swine flu outbreak in 2009, also reported severe obesity as an independent risk factor for increased mortality with infection. The Covid-19-Associated Hospitalization Surveillance Network has collected clinical data on Covid-19-associated hospitalised patients in the US. Among patients aged 18–64 years, obesity was the most prevalent underlying condition. Data from previous viral pandemics, combined with new emerging data on Covid-19, indicates the importance of including severe obesity in risk group calculations.

GlobalData epidemiologists have analyzed the proportion of men and women over the age of 18 years across the nine major markets (9MM: US, France, Germany, Italy, Spain, UK, Japan, China, and South Korea) who are severely obese (Figure 1). GlobalData epidemiologists estimated 27 million individuals over the age of 18 years across the 9MM to be obese in 2020, which corresponds to 1.5% of the total population. The US has the highest proportion of individuals who are severely obese in the 9MM with a total prevalence of approximately 8%. GlobalData epidemiologists found that the UK has the second-highest proportion of its population that is severely obese, with an approximate total prevalence of 2.5%. The prevalence of severe obesity within a population is important to help a country gauge the number of people at risk of serious Covid-19 that may require hospital admission.

Most early studies looking at risk factors for Covid-19 in China did not report severe obesity as a main independent risk factor, which is most likely due to China reporting a lower total prevalence of severe obesity than most western countries. With a higher prevalence of severe obesity shown across the US and Europe, areas where Covid-19 confirmed cases are now most notably high, it is vital that severely obese patients are understood as a risk group.

Health systems are becoming increasingly overwhelmed by the number of Covid-19 patients requiring treatment within intensive care units (ICUs), and the high number of severely obese people in many populations will be adding additional strain. The World Obesity Federation has also reported that further pressure is coming from severely obese patients, due to a lack of specialist beds, issues obtaining diagnostic images, and difficulties positioning and transporting patients. High severe obesity rates could be contributing to high death rates in certain countries, so it is vital these countries protect this vulnerable risk group, as a way of reducing the number of deaths from Covid-19.