COVID-19 and obesity: link, health outcomes

COVID-19 is a new viral infection that has spread quickly to most parts of the world. As of 7 May, the disease had killed over 2.6 lakh people globally.

COVID-19 was first reported in China, in December 2019. Since then, we’ve learnt quite a few things about the disease. For instance, we know that mild symptoms of COVID-19 are seen in 80% of symptomatic patients. These patients are unlikely to die due to this respiratory illness.

We also know from mortality studies that older people, especially older men, and those with comorbidities such as hypertension (high blood pressure) and diabetes are at increased risk of severe illness if they contract COVID-19. (Read more: COVID-19 prevention tips for the elderly and those living with comorbidities)

Now, the latest research is showing that those who are overweight or obese make up a disproportionate number of people who are hospitalized due to COVID-19.

While obesity is correlated with conditions such as hypertension, research suggests that obesity by itself also worsens health outcomes in COVID-19. Specifically, hospital admissions for those under 60 years of age increase with a rise in BMI; for older populations, the correlation is not as pronounced.

What is obesity?

BMI (body mass index) is a helpful indicator to conduct comparative health analyses across populations. It is calculated by dividing weight in kilograms by the square of height in meters. Someone with BMI over 25 kg/m2 is considered overweight and someone with BMI more than 30 kg/m2 is considered obese.

According to the National Family Health Survey (NFHS-4) published in 2015, obesity rates in India have risen alarmingly: they have doubled in the last decade from 2005-2015. Roughly 20% of women are obese, as are around 19.6% of men. Note that the MoFHW (Ministry of Family Health and Welfare) considered a BMI over 25 to indicate obesity.

Can body weight affect the outcome in COVID-19 patients?
Obesity and younger COVID-19 patients
Why does obesity lead to more severe COVID-19 outcomes?
Doctors for COVID-19 and obesity

Can body weight affect the outcome in COVID-19 patients?

A major study published in JAMA, a peer-reviewed journal brought out by the American Medical Association, in mid-April found that 42% of 5,700 patients admitted to New York hospitals were obese. Similarly, a UK surveillance study found that 75% of 6,720 hospitalized patients were in the overweight to obese category.

Data from elsewhere provide corroborative evidence. A Chinese study that looked at the health outcomes of 112 patients found that those who were overweight or obese were five times more likely to die than those who were not. Preliminary findings from another Chinese study suggested that overweight and obesity doubled the likelihood of developing severe pneumonia, especially in men.

In France, a study of 124 patients admitted to the ICU found that nearly half were obese. This was significant since other patients admitted to ICU for respiratory distress unrelated to COVID-19 were half as likely to be obese. Other data comparing obese COVID-19 ICU patients to baseline ICU patients suggests that obesity can make one more vulnerable to severe illness if one catches the new coronavirus infection.

Another large study involving over 4,000 patients in the US found that a BMI over 40 presented the highest hospitalization risk, along with old age. According to Dr Leora, one of the lead authors of the study, obesity is a stronger determinant for hospitalization than coronary disease, cancer, kidney disease or even pulmonary diseases. However, it presents most often with hypertension and diabetes, meaning its influence may not be independent. Dr Leora also added that obesity seems to be linked more strongly to hospitalization than death.

Obesity and younger COVID-19 patients

A study published in The Lancet on 4 May 2020 looked at 265 hospitalized COVID-19 patients. Interestingly, the researchers found an inverse correlation between age and BMI; the younger patients were more likely to be obese. The mean BMI was 26 kg/m2 and 25% exceeded a BMI of 34.7 kg/m2.

An NYU Langone study conducted a retrospective analysis of 3,615 patients admitted to hospitals across New York and disaggregated data by BMI. According to the findings, those under 60 years of age but with a BMI between 30-34 were twice as likely to be admitted to hospital than those with a BMI under 30. Further, those with a BMI over 35 were up to 3.6 times more likely to be admitted to the hospital than those with a BMI of less than 30. Importantly, this association between BMI and more serious illness was not found for those over 60 years of age.

These are initial findings and further research is required to scrutinize this data. However, it does appear that obese people under 60 are a vulnerable population.

Why does obesity lead to more severe COVID-19 outcomes?

Obesity is not a simple matter of high caloric intake in relation to low levels of activity. Advances in research have shown that obesity is a result of complex interactions between genetic, hormonal, behavioural, social and environmental factors. Therefore, it is difficult to ascertain the exact mechanisms of why obesity complicates COVID-19 cases. Obesity is associated with high-risk underlying conditions such as hypertension and diabetes which might explain some of the data above.

On a broader level, obesity leads to a chronic state of inflammation within the body that can impair the functioning of the immune system. This makes it difficult to ward off pathogens, including SARS-CoV-2 which causes COVID-19. The low-grade circulation of cytokines (which is the result of widespread inflammation) also weakens the body.

In the past, outbreaks of infectious diseases have shown that obese people are more vulnerable. In the H1N1 Swine flu pandemic of 2009, obese people were more likely to fall more seriously ill. Concerningly, the vaccine that was developed was also less effective for the obese.

Being overweight can also adversely affect lung function: excess weight in the abdominal region makes it harder for the lungs to pump oxygen into the body. Lower blood oxygen levels may exacerbate the symptoms of COVID-19. (Read more: What is oxygen therapy?)

There are practical issues, too; it is more challenging to intubate obese patients, meaning that ventilators are not able to perform optimally. It is also more difficult to conduct imaging tests such as X-rays and CT scans, adding diagnostic complications. (Read more: Risk of intubation and ventilators for COVID-19 patients)

For those who are short of breath, lying on the stomach can help relieve some distress, but this often does not work for those are obese.