New research has found  a high body mass index (BMI), rather than high blood sugar levels, are associated with excess risks of COVID-19 infection and long COVID.

The results of the study of over 30,000 UK adults from nine large prospective cohort studies, was presented at the European Association for the Study of Diabetes (EASD) Annual Meeting in Stockholm, Sweden

Led by Dr Anika Knuppel from the MRC Unit for Lifelong Health and Ageing, University College London, the research sheds new light on the impacts of the pandemic.

“Early in the pandemic research identified diabetes and obesity as risk factors for becoming severely ill with COVID-19. And we know that many people living with type 2 diabetes are also carrying excess weight. Our early findings support the idea that obesity-related mechanisms may be responsible for the excess risks of COVID-19 associated with diabetes, rather than high blood sugar per se,” explained Knuppel.

Previous research showed that people with diabetes and obesity are more likely to become severely ill and die if they catch COVID-19 but are no more likely to contract it. However, the underlying mechanisms, and their role in prolonged post-COVID-19 symptoms (long COVID), remains unclear.

To find out more, researchers looked for associations between a range of clinical characteristics measured before the pandemic—HbA1c (average blood sugar level), self-reported or medication-based diabetes, body mass index (BMI) and waist-to-hip ratio (WHR)—and self-reported COVID-19 infection and long COVID in nine ongoing UK cohort studies [1].

The analyses included the most recent measurements (taken between 2002 and 2019) of HbA1c, weight, height, waist and hip circumference from each study as well as information from questionnaires on health and lifestyle.

Participants reported having COVID-19 based on a positive test or strong suspicion. Long COVID was defined as symptoms that went on or affected functioning for longer than four weeks post-infection and was compared to those reporting symptoms for less than four weeks.

Where possible, associations were adjusted for sex, smoking, ethnicity, income, and education at the time of measurement.

Between May 2020 and September 2021, 5,806 participants reported ever having COVID-19, and 584 reported having long COVID (around 7% of COVID-19 cases with information on symptoms length).

Analysis of data from 31,252 participants in nine studies found higher BMI was associated with greater odds of COVID-19 infection—with the risk 7% higher for each 5kg/m2 increase in BMI. People with overweight (BMI 25-29.9kg/m2) and obesity (30 kg/m2 or greater) had 10% and 16% greater odds of COVID-19 infection, respectively, than healthy weight individuals.

Similar results were observed for long COVID (4,243 participants, six studies)—with the risk 20% higher for each 5kg/m2 increase in BMI.

“Our early findings suggest a link of adiposity with COVID-19 infection and long COVID-19 even after taking into account socio-demographic factors and smoking. We need to further explore what makes people with overweight and obesity at risk of worse outcomes and how this relates to severe cases”, said Knuppel.