Obese people hospitalised with coronavirus are almost 40pc more likely to die than other patients, the first major study in Britain has found.
Researchers said the findings also suggest that for patients who end up in hospital with Covid-19, the virus is just as deadly as Ebola.
The research on almost 17,000 cases admitted to hospital found that excess weight is one of the most deadly risk factors.
The study, led by Liverpool University and involving Imperial College London, which involved 166 UK hospitals, found the average age of coronavirus patients admitted to hospital was 72.
Overall, 49pc of patients have so far been discharged alive, 33pc have died and 17pc were still receiving care when the results were reported.
Chief investigator Prof Calum Semple, from the University of Liverpool, said Covid-19 was an "incredibly dangerous disease".
He said: "Crude hospital case fatality rate is of the same magnitude as Ebola. And people don't get this.
"If you come into hospital with Covid disease and you're sick enough to be admitted, crude case fatality rate is sitting somewhere between 35pc and 40pc. And that's the same crude case fatality rate for someone admitted to hospital with Ebola."
Some 60pc of those admitted were male, and women were 20pc more likely than men to survive.
The research, which has yet to be peer-reviewed, found almost half of cases lacked any underlying health condition or extra risk.
But when patients admitted to hospital were obese, their risk of death rose by 37pc.
Prof Semple said those who were obese with a body mass index (BMI) over 30 "do particularly badly from Covid disease, so they're more likely to go on to the intensive care units and to go on to die".
There were many reasons why obese people may have a "very tough ride" if they catch the virus, he said.
"The disease will cause problems in their lungs and hearts and kidneys for complex reasons, because fat cells secrete chemicals that essentially increase the inflammatory state of the body," he said.
He added it was also striking that the disease affected men much more than women, with the gap widening with age.
Those with dementia had death rates 39pc higher than other patients, while heart disease patients faced a 31pc increased risk. Death rates in patients admitted over the age of 80 were 14 times as high as those among the under-50s. And risks for those in their 70s were 10 times that of those under 50.
The study tracked 16,749 patients admitted to hospital with Covid-19 between February 6 and April 18 this year.