Covid-19 impacts overweight people more severely, finds Lancet study

Being overweight is associated with an increased risk of worse outcomes from Covid-19, including higher ICU admissions, according to a study published in The Lancet Diabetes & Endocrinology journal.

The researchers from the University of Oxford in the UK noted that this is the first large study to report the effect of bodyweight on risk of worse outcomes from Covid-19 across the full range of body-mass index (BMI).

BMI is a measure of body fat calculated by dividing a person's weight in kilogrammes by the square of height in metres.

The study is based on more than 6.9 million people living in England and included data from over 20,000 Covid-19 patients who were hospitalised or died during the first wave of the pandemic in the country.

The researchers found that the risk of worse outcomes from Covid-19 start rising in people with a BMI above 23 kilograms per square metre (kg/m2), which is considered to be in the healthy range.

The risks of hospitalisation were 5 per cent higher for each one unit increase in BMI and the risk of ICU admission was 10 per cent higher for each unit increase, they said.

People who were underweight (BMI less than 18.5) also experienced worse outcomes from Covid-19, they said.

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The effect of excess weight on the risk of severe Covid-19 was greatest in young people aged 20 to 39 years of age and decreased after age 60, according to the study.

Increasing BMI had very little impact on the risk of severe Covid-19 in people aged over 80 years, the researchers said.

However, the overall incidence of severe Covid-19 among people aged 20 to 39 years of age was lower than all other age groups, they said.

"Our study shows that even very modest excess weight is associated with greater risks of severe Covid-19 complications and the risks rise sharply as BMI increases," said Carmen Piernas, lead author of the study, from the University of Oxford.

"We also show that the risks associated with excess weight are greatest in people aged under 40 years, while weight has little to no effect on your chances of developing severe Covid-19 after age 80," Piernas said.

These findings suggest that vaccination policies should prioritise people with obesity, especially now the vaccine is being rolled out to younger age-groups, the researchers said.

Previous studies have reported that obesity is associated with more severe outcomes after infection with the SARS-CoV-2 virus, but this is the first to examine the consequences of excess weight on Covid-19 outcomes across the full range of BMI.

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It is based on anonymised health records from 6,910,685 community-based patients in the QResearch database of routinely collected electronic patient health records in England.

All of the participants included in the study were 20 years or older and had at least one BMI measurement on their record. The average BMI across the whole study group was 26.8 kg/m2.

The researchers analysed records between 24 January and 30 April, 2020 for outcomes linked to severe Covid-19 disease.

"We don’t yet know that weight loss specifically reduces the risk of severe Covid-19 outcomes, but it is highly plausible, and will certainly bring other health benefits," said Professor Paul Aveyard, who co-led the study, from University of Oxford’s Nuffield Department of Primary Care Health Sciences.

The researchers noted several limitations to their study.

The analysis of the impact of BMI may be limited by the smaller sample of people with recent BMI measurements, they said.

However, the findings did not change when the researchers excluded BMI measurements that were more than a year old at the start of the study period.