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March 4, 2021 | 6 minute read

Obesity Raises Risk for Both COVID-19 and Cancer

If it seems like the COVID-19 pandemic is no time to think about obesity, think again.

Rising Rates of Obesity Include Young Adults

Statistics on obesity in young adults are alarming. In 2000, over 30 percent of adults had obesity and now, the prevalence of obesity has risen to over 42 percent of adults. Obesity is just as common among people ages 20-39 as in those who are 40-59 or 60 and older.

Severe obesity is increasing, too, and now affects 9.2 percent of adults. It is defined by a body mass index (BMI) of 40 or higher (for example, someone who is 5’6” and weighs 247 lbs. or more, or someone who is 5’10” and weighs 278 lbs. or more). Severe obesity is more common in adults 20 to 59 years than in older adults.

Obesity Increases Risk of Severe COVID-19 in Younger Adults

You may often hear of obesity as a risk factor for heart disease and type 2 diabetes. But amidst the COVID-19 pandemic, the Centers for Disease Control and Prevention (CDC) warns that adults with excess body fat face increased risk of severe illness with COVID-19.

Compared to adults with a healthy BMI, those with obesity are:

  • More likely to be hospitalized due to COVID-19.
  • More likely to require mechanical ventilation and to be admitted to the ICU due to COVID-19.
  • At greater risk of dying from COVID-19.

Among people in the American Heart Association nationwide registry of people hospitalized with COVID-19 who were 50 years old and younger, 85 percent either had obesity or overweight. Younger adults may not consider themselves as being at high risk for severe COVID-19, but obesity-related risk of mechanical ventilation or in-hospital death rises even more sharply among younger adults.

How Does Excess Body Fat Increase the Severity of COVID-19?


  • Increases receptors through which the SARS-CoV-2 virus enters cells, which may increase viral load and increase risk for progression to severe disease.
  • Reduces the ability of the immune system to respond to infections.
  • Often leads to chronic, low-grade inflammation. The resulting oxidative stress and “cytokine storm” of inflammation-promoting compounds circulating through the body can damage blood vessels and cause formation of dangerous clots.
  • Changes lung mechanics, decreasing lung capacity and making ventilation more difficult.
  • Promotes high blood pressure and diabetes. People with these pre-existing conditions are two to more than six times more likely to develop severe COVID-19 symptoms than people with no pre-existing risk factors.
  • Can carry a stigma. People with obesity who have experienced weight bias or felt they were not treated with respect by healthcare providers may avoid or delay accessing health care. And that delay can have serious consequences.

Obesity Increases Risk of Cancer in Younger Adults

Risk of most cancers is strongly linked with increasing age, but cancers that once occurred mainly at older ages have been increasing in younger adults. Recent reports have particularly highlighted rising rates of obesity-related cancers in relatively young adults.

News stories about these shifts in cancer development have not always communicated them in accurate context. Cancer still occurs more often in older adults than young adults and obesity-related cancers are increasing in all age groups.

The key point is that adults under age 50, who may have considered themselves low-risk for cancer, need to recognize that cancer risk is something that warrants attention now, not later.

Whether measured by BMI, waist size or weight gain, excess body fat increases risk of at least 12 different cancers including mouth/pharynx/larynx, esophageal (adenocarcinoma), stomach (cardia type), colorectal, liver, gallbladder, pancreatic, breast (postmenopausal only), endometrial, ovarian, kidney, and prostate (advanced forms).

A recent study that analyzed data on cancer incidence in people ages 15 to 39 found significant increases in a little over a decade for 10 out of the 11 obesity-related cancers investigated.

Colorectal cancer is an important example calling for changes in our perspective. Although this cancer is the third most common cancer in both men and women, incidence has been declining – largely due to increased screening.

  • Decreased incidence among older adults is driving this trend. Among adults under age 50, rates of colorectal cancer are rising.
  • Since obesity is a major risk factor for colorectal cancer, increasing rates of obesity are considered an important influence behind increased colorectal cancer among young adults. Reasons for the rising rates among young adults are not clear, and more research is needed.

Obesity can increase risk of cancer in several ways. For young adults, some of the most important may be:

  • Body fat is not just a “spare tire”. It’s an active tissue producing hormones that can promote cancer development, as well as signaling proteins (cytokines) that promote chronic, low-grade inflammation that increases cancer risk.
  • Inflammation can lead to oxidative stress, with highly active molecules that can create cell damage that opens the door to cancer development.
  • Excess body fat can cause insulin resistance, which causes the body to produce elevated amounts of insulin and growth factors that lead to cancer development.

How to Address the Double Trouble of Obesity in Young Adults

The most urgent need is for all adults with excess body fat – especially those with a BMI categorized as obesity – to recognize that they are at increased risk of severe illness from COVID-19. Be sure to always:

  • Use masks, wash hands and physical distance from others to limit exposure to the virus.
  • Follow your healthcare provider’s recommendations about taking medications, healthy eating and physical activity.
  • Keep a 30-day supply of medicines on hand, and stock your cabinets and freezer with healthy foods you can prepare easily if you need to stay home.

Don’t let panic and fear over increased risk of severe COVID-19 and of cancer prompt you to turn to ineffective strategies for protection.

  • According to the Centers for Disease Control and Prevention, there’s no evidence that people can catch COVID-19 from food. The CDC advises against disinfecting food packages. Coronaviruses need a live animal or human host to multiply and survive, and cannot multiply on the surface of food or food packages. There’s no reason to disinfect food packaging.
  • Evidence does not support using vitamin C or other supplements to prevent COVID-19 or enhance its treatment. Likewise, research does not show benefits of supplements to reduce cancer risk. Prolonged or excessive supplementation of some nutrients that are promoted as supporting immune function can actually be harmful. Talk to your healthcare provider if you are uncertain whether more time indoors could mean foods aren’t meeting your needs for vitamin D.

Eating and physical activity habits encouraged in the AICR Cancer Prevention Recommendations are consistent with the current best advice to help support your immune system. Take a pass on “immune-boosting” hype and understand that eating habits don’t need to be “perfect” – whether to reduce risk of cancer or COVID-19. Small steps for better choices make a difference.

If this is the time for a fresh look at creating a health-protective lifestyle that helps reach and maintain a healthy weight as well, check out AICR’s free Healthy10 Challenge. It provides step-by-step support online for 10 weeks to help you build healthy and sustainable lifestyle habits.

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