Obesity increases the risk of death from Covid-19 by nearly 50% and may make vaccines against the disease less effective, according to a comprehensive study using global data.
The research from leading global experts warns that the risks for people with obesity are greater than previously thought.
The study, commissioned for the World Bank, will increase the pressure on governments to tackle obesity, including in the UK where the prime minister, Boris Johnson, has put himself at the head of a drive to reduce the nation’s weight.
The study from the University of North Carolina at Chapel Hill finds that people with obesity, with a BMI over 30, are at greater risk from the coronavirus in every way. Their risk of ending up in hospital with Covid-19 is increased by 113%, they are more likely to be admitted to intensive care (74%) and have a higher risk of death (48%) from the virus.
The study is led by Prof Barry Popkin, of the department of nutrition at the UNC Gillings Global School of Public Health, who told the Guardian he was shocked by the findings. The risk of dying from Covid-19 for people with obesity was significantly higher than anyone had thought.
“That’s a pretty big effect, for me,” said Popkin. “It is a 50% increase essentially. That’s a pretty high scary number. All of it is actually – much higher than I ever expected.”
The risk of being admitted to hospital for people with obesity was doubled, he said, at 113%. “That, ICU admission and mortality are really high,” he said. “They all shocked me, to be honest.”
The study, published in the journal Obesity Reviews, is a meta-analysis, bringing together data from many studies carried out around the world, including Italy, France, the UK, the US and China. Obesity is a global problem that no country has yet successfully tackled.
How to find out if you are obese and your BMI is a problem
Obesity is measured by body mass index (BMI), which for an adult is a ratio of weight in kilograms by height in metres squared. The NHS has an online calculator. It does not work for children who are still growing and it is often regarded as a blunt instrument for individuals, because some very fit people have bulky muscle tissue that will make them heavier. But for most people and for looking at populations as a whole, it is a useful indicator of healthy or unhealthy weight.
Normal weight is a BMI of 18.5 to 25. Below that you are underweight, which is also unhealthy. Between 25 and 30, an adult is considered overweight. BMI of 30 to 40 is obese. Anyone with a BMI higher than that is considered severely or morbidly obese and in need of medical intervention, such as bariatric surgery.
The categories are not exactly the same for people from black, Asian and other minority ethnic groups, who have a raised risk of obesity-related diseases such as type 2 diabetes with a BMI of 23 and a high risk at 27.5.
You can also find out whether you are obese with a tape measure. Carrying fat around your stomach is a significant risk for heart disease, type 2 diabetes and stroke. To measure your waist, put the tape around the midpoint between the bottom of the ribs and top of the hips and breathe out naturally.
If a woman’s waist is 80cm (31.5ins) or more or a man’s is 94cm or more, they would be advised to lose weight. A waist of 88cm or more for women or 102cm or more for men puts you at very high risk and you should speak to your GP.
Sarah Boseley Health editor
People with obesity often have underlying medical conditions that put them at greater risk from the coronavirus, such as heart disease and type 2 diabetes. Obesity can cause metabolic changes, such as insulin resistance and inflammation which make it harder for the body to fight off infections.
“All of these factors can influence immune cell metabolism, which determines how bodies respond to pathogens, like the Sars-CoV-2 coronavirus,” said co-author Prof Melinda Beck. “Individuals with obesity are also more likely to experience physical ailments that make fighting this disease harder, such as sleep apnoea, which increases pulmonary hypertension, or a body mass index that increases difficulties in a hospital setting with intubation.”
Any vaccine developed for Covid-19 may not work as well in people with obesity, say the authors.
“We know a Covid vaccine will have a positive effect on obese people but we suspect from all our knowledge from tests on the Sars vaccine and the flu vaccine it will have a diminished benefit compared to the others,” said Popkin.
They had convinced the Centers for Disease Control which oversees public health in the US that people with obesity were not getting the full benefit of standard flu vaccines, he said. “We now have a stronger flu vaccine for overweight people,” he said.
The recommendation was brought in this year after a long campaign. There is now an extra booster shot for people who are overweight as well as the elderly, whose immune systems weaken with age.
Popkin said vaccine developers should look at the data from their clinical trials for the obesity effect, even where they have an overall benefit. “They might just then have to consider this and do some testing in the vaccine to get it to work better for obese people.”
The hardship caused by lockdowns and loss of income for people around the world is also increasing the risk of people becoming obese, say the authors.
“We’re not only at home more and experience more stress due to the pandemic, but we’re also not visiting the grocery store as often, which means the demand for highly processed junk foods and sugary beverages that are less expensive and more shelf-stable has increased,” Popkin said.
“These cheap, highly processed foods are high in sugar, sodium and saturated fat and laden with highly refined carbohydrates, which all increase the risk of not only excess weight gain but also key non-communicable diseases.”
Source: The Guardian