In June this year we reviewed evidence published throughout the COVID-19 pandemic that suggested a potential link between obesity and severity of COVID-19. Since then, evidence has continued to emerge, and while some limitations remain, it has become clear: there is an association between obesity, severity and worse outcomes from COVID-19.
At the end of July, Public Health England released a report providing evidence-based insights into the relationship between excess weight and COVID-19, garnered from new evidence. They found an increased association with testing positive for COVID-19 as BMI increases above a healthy range, with a stronger relationship observed in BAME groups than in White ethnic groups. They also found that patients with a BMI in the overweight or obesity categories are more likely to be admitted to intensive care than those with BMI in the healthy range or below. They are also more likely to require advance treatment for severe symptoms. Finally, they found a potentially higher risk of COVID-19 related death with increasing BMI, which has persisted in studies adjusted for confounding factors such as age, sex, measures of socio-economic status (SES), ethnicity and co-morbidities.
The UK Intensive Care National Audit and Research Centre (ICNARC)1 has continued to report a relationship between critical illness from COVID-19 and obesity, with 39.3% of ICU patients with COVID-19 classed as having obesity. Researchers have also used data from the UK Biobank, a large set of data following half a million volunteers, finding that testing positive for COVID-19 is also associated with obesity2.
Observations made in UK studies are consistent with international evidence; global evidence consistently highlights an association between obesity and COVID-19 hospitalisation, severity, admission to ICU, and death.
Why might people be at higher risk of complications?
Researchers have identified a number of potential mechanisms that may explain the link between obesity and COVID-19:
Ethnicity, area deprivation and inequalities
Since our last evidence review, more research has emerged on the link between ethnicity, area deprivation, inequalities and COVID-19. There are long-standing health inequalities in the UK that researchers believe have been exacerbated by the coronavirus pandemic, including those related to ethnicity and socio-economic deprivation.
Children living in the most deprived areas of Scotland have more than double the risk of obesity than those in the least deprived areas (13.7% vs 6.5%)3, with a similar gap seen amongst children in England4. This gap also exists for adults in Scotland3 and England4.
Evidence is emerging for an association between obesity, socioeconomic status and COVID-19, showing a social gradient with poorer outcomes for those from more socio-economically deprived areas, which is likely multifactorial:
This is backed up by recent ICNARC data, which shows that around a quarter of patients diagnosed with COVID-19 and in ICU were from the most deprived fifth of the population, compared to 14.4% from the least deprived fifth1. This disparity is evident across all ethnic groups, however is much more pronounced in those of Non-White ethnicity compared to White individuals.
There is also a disparity in prevalence of obesity between different ethnic groups. In children in England, obesity prevalence is highest for Black children across both year groups measured (reception and year 6)5, while in Scotland, Black children are more likely than White children to have a high BMI6. Again, this is also observed in adults7.
Researchers have found that while the risk of testing positive for coronavirus was associated with BMI both in BAME and White ethnic groups, as BMI increased over 30 (obesity category), the likelihood of testing positive was far higher in BAME individuals than in White individuals8. Sattar et al recorded the same findings, and additionally found that BMI was more strongly related to COVID-19 death in Non-White individuals (predominantly South Asian and Afro-Caribbean), than White individuals9.
Obesity has well-established links with adverse health outcomes from a range of co-morbidities. Evidence emerging during the coronavirus pandemic suggests similar associations; obesity has been consistently linked to increased severity of COVID-19 and increased risk of death, with multiple potential and plausible mechanisms identified. Nevertheless, there are limitations in the evidence which should be taken into account when making recommendations10. Further research is required to explore the extent to which ethnicity and deprivation contribute to increased severity and risk of death from COVID-19.
As more data on co-morbidities and demographics of patients with confirmed COVID-19 is analysed, risk factors can be determined and groups most at risk from the virus can be identified clearly. This information can be used to tailor prevention measures toward groups who require the most protection.
Read our new briefing, Obesity and COVID-19, jointly published with the Royal College of Physicians and Surgeons of Glasgow.