Aside from older age and male gender, obesity is one of the most important risk factors for severe Covid. Compared to those with a healthy BMI, the obese (those with a BMI greater than 30) are about twice as likely to end up in the ICU, and are about 20% more likely to die.
Which raises the question: is obesity a modifiable risk factor? Can obese people reduce their risk of severe Covid by losing a large amount of bodyweight? While the answer might seem obvious, it isn’t necessarily ‘yes’.
Rather than obesity per se, it might be some factor strongly correlated with obesity that predisposes you to severe Covid. Or perhaps obesity leads to permanent changes in the body, so that even once you lose the extra bodyweight, you’re still at higher risk than someone who was never obese to begin with.
It’s certainly possible. Yet a new study suggests that obesity is a modifiable risk factor. Ali Aminian and colleagues examined a cohort of obese people who’d had gastric bypass surgery at particular hospital in Cleveland between 2004 and 2017.
Members of this cohort were matched to similar individuals who’d never had gastric bypass surgery. Matching was based on age, sex, race, BMI at the time of surgery and an index of comorbidities.
The researchers therefore compared two groups: obese people who’d lost weight thanks to gastric bypass surgery; and obese people who’d never had gastric bypass surgery. Note: most members of the surgery group were still obese by the time of the pandemic. Their average BMI was 38, compared to 46 in the control group.
The groups were compared with respect to their Covid outcomes during the first year of the pandemic. What did the researchers find? Their main results are shown in the figure below.
The two groups had almost identical infection rates, as shown in the top-left chart. However, the incidence of severe Covid was much higher in the control group, as shown in the other three charts. This provides relatively strong evidence that losing weight does reduce the risk of severe Covid.
So far, governments have made very little effort to encourage weight loss during the pandemic. (One exception is a recent campaign by the tech-savvy government of El Salvador.) In fact, the net effect of Britain’s lockdowns has been to increase the rate of obesity.
But if Aminian and colleagues’ findings hold up, more emphasis on weight loss is clearly warranted – especially since obesity is risk factor for various medical conditions, not just Covid.
Of course, the main obstacle to promoting weight loss in the current year is not lack of evidence, but concerns around ‘fat-shaming’. To reduce stigma around obesity, you’re supposed to affirm that people can be ‘healthy at any size’. Unfortunately for the activists, this simply isn’t true.
Reducing obesity isn’t a silver bullet in the fight against Covid. But it would certainly help.