30 CLINICAL
Mythbuster
Debunking common patient myths and misconceptions
‘ You will suffer less with Covid-19 if you lose weight ’
T he link between body mass index ( BMI ) and Covid-19 is not clear . Frightening people into believing they will be protected if they lose weight may do more harm than good .
We ’ ve read the headlines and watched the Prime Minister ’ s address at the Conservative party conference , where he said his experience of Covid-19 was worse because he was ‘ too fat ’. It seems accepted that obesity is one of the biggest factors in Covid-19 hospitalisations . But sweeping statements such as that made by Boris Johnson , with little evidence , can be harmful .
When the health secretary Matt Hancock stated ‘ everyone who is overweight should lose at least 5lb in order to save countless lives and spare the NHS a £ 100m cost ’, it became clear the Government believes that being ‘ overweight ’ and ‘ obese ‘ is a choice for many . But this fat-shaming could lead to people with a higher body weight developing habits that could lead to health issues , such as yoyo dieting . Health is not a certain body size . It is more important for people to have a healthy relationship with food .
The evidence so far Given the conventional wisdom that obesity is harmful , it seems reasonable to assume a higher body weight increases the risks of Covid-19 . 1 The evidence , however , remains inconsistent and it is possible an obesity survival paradox may exist , as with other conditions . 2 , 3 , 4
The published research linking BMI to Covid-19 is not conclusive . Most studies do not take into account the social determinants that predict health outcomes more strongly than body weight 5 – social class , racism , sexism , trauma and negative weight-related attitudes . These factors , which lead to cardiovascular disease , type 2 diabetes , cancer , asthma or other chronic respiratory conditions , could increase the risk if you become Covid-positive , rather than fatness itself . 6 , 7
When social determinants and co-morbidities are accounted for , death rates appear lower in higher BMI groups 8 – hence the obesity survival paradox referred to earlier . A recent American study shows obesity , black race , Hispanic ethnicity , chronic lung disease and hypertension were not associated with mortality due to Covid-19 . But the study has an acknowledged limitation – the male subjects had access to a national healthcare system and may not be representative of the general US population .
A 2017 meta-analysis found that having a BMI of 30 or above was correlated with a significantly lower risk of dying from acute respiratory distress syndrome ( ARDS ), compared with those in the ‘ normal ’ category . 9 A retrospective study this August reported BMI over 40 was more strongly associated with Covid-19 deaths in men , but not in women . 10
Following the first epidemic , UK tabloid publications reported on data from the Intensive Care National Audit and Research Centre . 11 For the first 200 critically ill patients , there was concern about the high percentage with a BMI over 30 . However , these percentages are simply reflective of the BMI spread of the general population . Data from China ( where Covid-19 emerged ) show no correlation between a high BMI and the development of Covid-19 . BMI is also not listed among the co-existing disorders in Covid-19 patients . 12 This is noteworthy because China would likely have highlighted a link between high BMI and Covid-19 because weight management there , as in the UK , is a public-health priority . Correlation does not mean causation .
When discrimination exists in healthcare it is evident that fatter people are often not given the same quality of care because their conditions are blamed on their weight . 13 , 14 This may also mean that fatter people avoid getting assessed for Covid-19 symptoms ( and perhaps this is one of the reasons they require hospitalisation ). Weight stigma does not motivate individuals to adopt healthier behaviours . 15
However , it is still possible that a high BMI is a risk factor for hospitalisation from Covid-19 . But this does not mean that trying to lose weight will definitely lower the risk of hospitalisation or death from the virus .
It is well known that many weight loss approaches eventually result in weight gain across all ages . 16 , 17 , 18 And weight cycling
( or yoyoing ) increases the risk of hypertension , heart disease and type 2 diabetes . 19 It ’ s definitely time to challenge
20 , 21
obesity research .
There is insufficient evidence that BMI is a significant risk factor for hospitalisation or death from Covid-19 . It would be more beneficial to support people in healthy eating , sensible eating patterns and exercise , then they are likely to achieve any weight loss they wish to achieve in a more sustainable way .
Mel Wakeman is a registered nutrition consultant and applied physiologist
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