Obesity Rates Linked to Severe Outcomes in COVID-19 Patients


New data show a link between body mass index and increased risk of adverse effects from COVID-19.

Carmen Piernas, MSc, PhD

Carmen Piernas, MSc, PhD

A recent study on the relationship between body mass index (BMI) and COVID-19 found that excess weight is associated with a substantial increase of severe COVID-19 outcomes.

Investigators, led by Carmen Piernas, MSc, PhD of the University of Oxford, found a linear increase in COVID-19 risk leading to hospital admission or death in patients with a BMI of more than 23kg/m².

The study examined the association of obesity and adverse outcomes after infection of SARS-CoV-2, in terms of demographic and behavioral characteristics, type 2 diabetes and other health conditions.

Patients in the large population-based cohort had an increased relative risk due to increased BMI if they were younger than 40 years and of Black ethnicity.


Investigators collected data from a research database of 1500 general practices (GP) in England on demographic, medical diagnoses, prescriptions, and laboratory results.

Patient data was collected between January 24, 2020 – April 30, 2020 in the QResearch Database, for patients aged 20 years or older who had available BMI data.

BMI was calculated as weight in kg divided by height in m squared (kg/m²). Follow-up occurred from an outcome of interest, death from other causes, or the end of the study period.

The outcomes of interest included admission to hospital for COVID-19, admission to the ICU for COVID-19, and death or suspected death due to COVID-19.

Investigators used a multivariable Cox proportional hazard models to obtain hazard ratios with 95% confidence intervals (CI). It was used to estimate the risk of severe COVID-19, adjusting for demographic factors, behavioral characteristics, and comorbidity.


Data from 10,594,000 patients from 2205 general practices were used in the study. The team found 6,910,695 (84.9%) had at least one BMI measurement (mean 26.78 kg/m²: SD 5.59).

In the study period, there were 13,503 hospital admissions and 5479 deaths due to COVID-19. A third of patients with severe COVID-19 outcomes were classified as having type 2 diabetes.

Investigators found a non-linear association between BMI and hospital admission and death due to COVID-19, while a linear association was found between BMI and ICU admission due to COVID-19.

The data showed each excess BMI unit above a BMI of 23 kg/m² was associated with increased risk of hospital admission (HR 1.05; 95% CI, 1.05 – 1.05), ICU admission (HR 1.10; 95% CI, 1.09–1.10), and death (HR 1.04; 95% CI, 1.04 – 1.05).

The team found age of patients was significantly associated with BMI and severe COVID-19 outcomes. Younger age groups had the highest HR, with a progressive decrease occurring in increasing age groups.

Each BMI increase above 23 kg/m² in patients aged 20 – 39 years was associated with an increased risk of hospital admission (HR 1.09; 95% CI, 1.08 – 1.10), ICU admission (HR 1.13; 95% CI, 1.11 – 1.16), and death due to COVID-19 (HR 1.17; 95% CI, 1.11 – 1.23).

Investigators also found Black people have a higher risk of hospital admission (HR 1.07; 95% CI, 1.06 - 1.08) compared to white people, (HR 1·04; 95% CI, 1·04 – 1·05), as well as the risk of death due to COVID-19, (HR 1·08; 95% CI, 1.06 – 1.10) versus (HR 1.04; 95% CI, 1.03 – 1.04).

Data show the risk of admission to hospital and ICU due to COVID-19 due to an increase in BMI was lower in people with type 2 diabetes, hypertension, and cardiovascular disease.


The team concluded the data show a significant positive linear association between BMI increases and admissions to ICU due to COVID-19.

Investigators said the association between BMI and adverse outcomes may be due to central fat accumulation in patients or difficulties in intubation and movement during care, which may affect recovery times, but no conclusive evidence was found.

“Although as yet unproven, interventions that reduce weight might reduce the risk of severe COVID-19 outcomes in individuals,” investigators wrote, “In the longer term, our findings highlight the need to work towards a healthy weight at a population level.”

In a comment accompanying the study, Krishnan Bhaskaran of the London School of Hygiene & Tropical Medicine said these lingering questions will help to inform the public health response to COVID-19 in the future.

“Key future research priorities will be to establish whether BMI affects vaccine efficacy, and to understand whether people outside the healthy BMI range (18.5 – 24.9 kg/m2) are at increased risk of post- COVID-19 sequalae,” Bhaskaran said.

The study, “Associations between body-mass index and COVID-19 severity in 6·9 million people in England: a prospective, community-based, cohort study,” was published online in The Lancet Diabetes & Endocrinology.

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