We've heard about the dangers of coronavirus for older people and those with chronic health problems like high blood pressure.
But new research is pointing to evidence that people affected by obesity or who are overweight might also make the impacts of COVID-19 more severe, particularly for those aged under 60.
The US Centers for Disease Control now lists people who are severely obese as being at a higher risk of complications from COVID-19.
In addition, data out of China has found that obese and overweight patients were five times more prevalent in the numbers of deaths, while a number of studies across the world have confirmed the risk.
- Research from New York University has found COVID-19 patients under 60 with obesity were almost twice as likely to need treatment in the ICU
- Severe obesity increases the risk of acute respiratory distress syndrome (ARDS), which is a major complication of COVID-19.
- In Australia, two-thirds of adults are classified as overweight or obese
Research from the UK's Intensive Care and National Audit and Research Centre showed almost three-quarters of patients admitted to intensive care were obese or overweight.
A study from New York University found obese COVID-19 patients who were under 60 were almost twice as likely to need treatment in the ICU.
University of Queensland virologist Kirsty Short said they were learning "more and more" about the disease on a daily basis.
"This is something that we've suspected for a long time based on our research with influenza," Dr Short said.
"With influenza, another respiratory virus, obesity is associated with increased risk of hospitalisation, increased risk of ICU admission and an increased risk of mortality, so it's perhaps not surprising that we are starting to see the same thing with COVID-19.
"The rate of knowledge [of this virus] is phenomenal."
The link between obesity and COVID-19 has serious implications for countries such as Australia, where two-thirds of adults are classified as overweight or obese.
Obesity is defined by a person's body mass index (BMI): a person's weight in kilograms divided by the square of their height in metres (kg/m²).
Why does obesity increase the risk?
The short answer: it's complicated.
People who are overweight or obese can have reduced lung function.
Severe obesity increases the risk of a serious breathing problem called acute respiratory distress syndrome (ARDS) — a major complication of COVID-19.
It can be more difficult for overweight people to breathe because of excess weight around the stomach.
People with obesity are also more likely to have other complicating illnesses like diabetes and cardiovascular disease.
Researchers also know COVID-19 increases the amount of inflammation in the body.
People with obesity have a higher level of inflammation in their bodies, which can impede the body's immune response and make it more difficult to fight coronavirus.
"When the virus comes and infects [them], then this low-grade inflammation seems to become more pronounced," Amanda Salis, a professor of obesity research at the University of Western Australia, said.
"That can contribute to this very strong immune response that's seen in COVID-19."
In a practical sense, it is also more difficult for frontline health workers to diagnose and treat people with obesity.
"Intubation — mechanical ventilation — is more difficult. X-rays and imaging are more difficult," Dr Salis said.
"One of the (treatments) used in COVID-19 is turning patients on their stomachs because that helps with expanding the lungs or getting more oxygen into the lungs and the blood and this can be difficult with people with a larger body mass index."
All of these factors can contribute to their poorer outcomes with the illness.
How worried should overweight or obese people be?
Experts are urging people to follow advice from health authorities about avoiding infection.
"What is very clear to us is that this is a very severe disease and you want to do everything you can in your power to prevent yourself from contracting it," Dr Short said.
Serious outcomes for COVID-19 can now be added to the long list of other diseases and complications including cardiovascular disease and asthma that are a consequence of obesity.
Cardiologist Aseem Malhotra said these risk factors could be "markedly improved" within weeks by adopting a healthy diet and cutting out junk food.
"Given our health systems are already stretched with obesity-related illnesses, there is no better time than now, to tell the public that the time to change their diet is now.
"Backed with policy changes that address the availability, affordability and acceptability of unhealthy foods, we could see marked changes in population health in a very short time."
"COVID-19 has really put a highlight on this because it's so sudden and so intense and so unexpected," Dr Salis said.
"But it does shine a light on the importance of obesity prevention at a public health level."