Obesity doubles the risk of hospital treatment for Covid-19 and increases the risk of dying by nearly 50%, according to a global analysis.
Obesity makes other diseases such as diabetes and high blood pressure more likely, according to US researchers.
With a weakened immune system, this can make these people more vulnerable to severe Covid-19.
They also warn that a coronavirus vaccine might be less effective in obese people.
This is based on the fact that flu shots don’t work as well in people with a body mass index (BMI) over 30.
The team, at the University of North Carolina, looked at data from 75 studies around the world for their research, including nearly 400,000 patients.
They found that people with obesity and Covid-19 were twice as likely to end up in hospital and 74% more likely to be admitted to intensive care. They were also at greater risk of dying from the disease caused by the coronavirus.
Studies in the UK have shown similar risks for overweight people, prompting the government to introduce new measures to tackle obesity.
Professor Barry Popkin, who led the study from the University of North Carolina’s nutrition department, said the increased risks of being obese and having Covid-19 were “much higher than expected.”
He said healthier eating should be a priority in many countries, with fewer sugary drinks and far less junk and processed foods in people’s diets.
Obesity is linked to a number of illnesses that also put people at a higher risk of contracting Covid-19.
It can also lead to more inflammation in the body, reducing the body’s ability to fight infections, and putting more pressure on other organs, as well as on breathing.
“Vaccine researchers should look at how it affects people who are obese,” Professor Popkin said of a coronavirus vaccine to protect against Covid-19.
He is concerned that a vaccine, when ready for use, may be less effective in a population with a high percentage of obese people.
With obesity on the rise globally and 20% of people being overweight or obese in almost every country – in the UK and US it is close to 66% – understanding how treatments and vaccines work in this group is “essential,” according to research.