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expert reaction to study looking at a potential link between body weight and risk of severe COVID-19, especially for younger adults

A study published in The Lancet Diabetes & Endocrinology looks at body-mass index and COVID-19 severity.


Comment on the study:

Prof Nick Finer, National Centre for Cardiovascular Prevention and Outcomes, UCL Institute of Cardiovascular Science, said:

“While the risk of severe complications (hospital and intensive care admission and death) in young people may be low, this very large study shows that obesity and even being overweight can substantially increase all of these risks. The impact of obesity was most marked in people in the youngest age range of 20-39 and rightly suggests that individuals with lower degrees of obesity in this age range should also be considered vulnerable, and prioritised for vaccination (alongside those with a body mass index over 35 already considered high risk).

It is a sobering comment on the lack of care provided to people living with obesity that the authors were unable to assess the potential benefits from weight loss due to the fact that ‘the number of participants reported to have been offered referrals to weight management programmes was low and weight change was poorly recorded’. The findings highlight the need to recognise that obesity is not just a chronic disease, but also a risk for acute illness or even death, and there is therefore a need to improve access to evidence-based treatments for people living with obesity.”

  • Does the press release accurately reflect the science?  YES
  • Is this good quality research?  Are the conclusions backed up by solid data? YES
  • Do you agree that ‘vaccination policies should prioritise people with obesity’? YES
  • How does this work fit with the existing evidence? Does it tell us anything new? Expands and amplifies the role of obesity as a risk factor – especially the disproportionately increased risk in the young
  • Have the authors accounted for confounders?  Are there important limitations to be aware of? YES – as far as they can
  • What are the implications in the real world?  Is there any overspeculation?   Important and no
  • Any other comments? This sort of real world study is a direct product of our NHS’s ability to undertake such research based on huge numbers of patients whose (anonymised) data are collected – something that is a triumph for British academic medicine.


Comment on the question if we should prioritise vaccination of those with obesity:

Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice Magazine, Immediate past Chair of the BMA Public Health Medicine Committee, said:

“Since Covid-19 came onto the scene some 14 months ago we have, of course, learned a lot more about it.

“We fairly quickly identified factors associated with increased likelihood of becoming infected, and of being more seriously ill if infected. Increasing age being the strongest factor.

“Other factors may have been identified anecdotally, or observed by clinicians, but have taken longer to be more formally quantified.

“In principle, the intention is to vaccinate people at greatest risk of more severe disease – hospitalisation, critical care, death – first, and to work from those at greatest risk to those at least risk. And since age is the strongest factor, this has meant working down from oldest to youngest.

“But the Joint Committee on Vaccination and Immunisation also included people with certain other factors in higher risk categories.1 People who were “clinically extremely vulnerable” were included in category 4, with people aged 70+, and those with “underlying health conditions” in category 6, with people aged 60+.

“Hypothetically, it might make sense to individually assess people, work out how their risk compares to people without underlying conditions, and slot them in with people whose age puts them at about the same risk.

“But another criterion for a successful, quick vaccination programme is avoidance of complexity. Complicating things tends to slow them down; so this rather broad-brush makes sense. It certainly made sense earlier on; perhaps things have changed.

“Now that we have already offered vaccination to people aged 40+, so younger people whose risk equates to that of somebody age 40 or more could logically be added in. So it would make sense to amend or add to the “underlying health conditions” list to include conditions which put younger people at that level of risk, so that people with those conditions could be vaccinated as soon as an appointment is available, without having to await vaccination with their age group.

“There are many similarities between the underlying conditions list for Covid-19, and the conditions (the “clinical risk groups”) qualifying people for influenza vaccination.2 Morbid obesity (“adults with a Body Mass Index (BMI) ≥40 kg/m2) appears on both lists. A notable omission from the Covid-19 underlying conditions that appear on the influenza clinical risk groups is pregnancy.

“I note that JCVI has already amended the underlying conditions at least once, to include people on the learning disability register.3 If obesity raises the risk of a 20 year old to be equivalent to that of a 40 year old, it would be logical to add lower levels of obesity to the list of underlying conditions. According to this study, 4 5 risk rises incrementally with BMI, and the paper appears to propose prioritising vaccination of people with a BMI ≥25 kg/m2. JCVI may choose to consider carefully what BMI cut-off to use.

“There are other conditions that might be worth adding to the underlying conditions list – not least pregnancy, now that there is evidence that pregnant women are no more likely to catch Covid-19, but more likely to have severe disease if they do6; and that vaccination in pregnancy is safe7 and effective8.

“One consideration, in any such decisions, goes back to the “how much more complicated would this make it” question. Body mass index is poorly recorded in medical records (cf pregnancy, which is very well recorded). So it may be harder to identify people with a BMI above the cut-off; whereas identifying pregnant women would be much simpler. This might be an argument against adding obesity to the list of underlying conditions; but I can’t see why it couldn’t be used for inviting patients for whom it is recorded.”


  1. Department of Health and Social Care. Joint Committee on Vaccination and Immunisation: advice on priority groups for COVID-19 vaccination, 30 December 2020. Independent report 2020; Updated 30 Dec 2020; Accessed: 2020 (30 Dec): ( or via
  2. Public Health England. Chapter 19: Influenza. Immunisation against infectious disease. 29 Oct 2020 ed. London: HMSO, 2019:1-27 (
  3. Public Health England. JCVI advises inviting people on Learning Disability Register for vaccine. PHE News Story 2021; Updated 24 Feb 2021; Accessed: 2021 (24 Feb): (
  4. Bhaskaran K. New insights into the association between body-mass index and severe COVID-19. The Lancet Diabetes & Endocrinology 2021. (
  5. Gao M, Piernas C, Astbury NM, Hippisley-Cox J, O’Rahilly S, Aveyard P, et al. Associations between body-mass index and COVID-19 severity in 6·9 million people in England: a prospective, community-based, cohort study. The Lancet Diabetes & Endocrinology. (
  6. Adhikari EH, Spong CY. COVID-19 Vaccination in Pregnant and Lactating Women. JAMA 2021;325(11):1039-1040. (
  7. Centers for Disease Control and Prevention. V-safe COVID-19 Vaccine Pregnancy Registry. Centers for Disease Control and Prevention (CDC) 2021; Updated 12 Apr 2021; Accessed: 2021 (17 Apr): (
  8. Gray KJ, Bordt EA, Atyeo C, Deriso E, Akinwunmi B, Young N, et al. COVID-19 vaccine response in pregnant and lactating women: a cohort study. American Journal of Obstetrics & Gynecology 2021. (


Comment on the study:

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“These data add to the overwhelming evidence from other sources (several hundred studies now in many parts of the world) that support excess body weight are an important, causal risk factor for more severe COVID-19 outcomes.  The new findings support that such risks increase in a linear fashion from normal BMI upwards, and that excess weight may be a stronger risk factor for severe COVID-19 in younger people as we reported before.  Without waist circumference measurements, I am not sure the authors can conclude whether belly fat is more strongly linked to risk, or not.  I suspect it may be but this needs more research. 

“There are also many potential mechanisms for such observations which include heavier people getting a bigger dose of the virus in the first place, to thicker blood, poorer metabolism (needed to help nourish immune cells and the brain) and an exaggerated immune response linked to excess adipose tissue.  Whether the findings mean people who are living with obesity should get vaccines earlier should be looked at by relevant authorities but such decision should be based on absolute risks.  The more important question is whether helping people lose weight will lessen their chances of severe complications in subsequent waves. The overwhelming evidence, aided by this study, suggests this would be the case. What most countries now need to do is upscale their lifestyle intervention policies to help more people, and to up prevention efforts.”



Associations between body-mass index and COVID-19 severity in 6·9 million people in England: a prospective, community-based, cohort study’ by Min Gao et al is published in The Lancet Diabetes & Endocrinology



All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Nick Finer: “I am employed by Novo Nordisk in Medical Affairs, a company that markets anti-obesity medications. However I speak here in my academic capacity”.

Dr Peter English: “my daughter is pregnant but is not yet eligible for vaccination”

Prof Naveed Sattar: “NS has written several papers on this topic and is involved in trials in patient with long-COVID, Also consulted for Eli-Lilly, Novo Nordisk and Pfizer.”     

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