The majority of global COVID-19 deaths have been in countries where many people are obese, with coronavirus fatality rates 10 times higher in nations where at least 50% of adults are overweight, a global study found.
Marion Nestle, Goddard Professor in the Department of Nutrition at New York University, discusses the U.S. food industry being in a highly competitive environment where profits are paramount and public health is not a priority.
But on its own, “BMI [body mass index] remains a strong independent risk factor” for severe COVID-19, according to several studies that adjusted for age, sex, social class, diabetes, and heart conditions, says Naveed Sattar, an expert in cardiometabolic disease at the University of Glasgow. “And it seems to be a linear line, straight up.”
- For starters, the blood of people with obesity has an increased tendency to clot—an especially grave risk during an infection that, when severe, independently peppers the small vessels of the lungs with clots
- Immunity also weakens in people with obesity, in part because fat cells infiltrate the organs where immune cells are produced and stored, such as the spleen, bone marrow, and thymus, says Catherine Andersen, a nutritional scientist at Fairfield University. “We are losing immune tissue in exchange for adipose tissue, making the immune system less effective in either protecting the body from pathogens or responding to a vaccine,” she says.
The impact extends to the 32% of people in the United States who are overweight. The largest descriptive study yet of hospitalized U.S. COVID-19 patients, posted as a preprint last month by Genentech researchers, found that 77% of nearly 17,000 patients hospitalized with COVID-19 were overweight (29%) or obese (48%). (The Centers for Disease Control and Prevention defines overweight as having a BMI of 25 to 29.9 kilograms per square meter, and obesity as a BMI of 30 or greater.)
There is consistent evidence that higher amounts of body fat are associated with increased risks of a number of cancers (6), including:
- Endometrial cancer: Obese and overweight women are two to about four times as likely as normal-weight women to develop endometrial cancer (cancer of the lining of the uterus), and extremely obese women are about seven times as likely to develop the more common of the two main types of this cancer (7). The risk of endometrial cancer increases with increasing weight gain in adulthood, particularly among women who have never used menopausal hormone therapy (8).
- Esophageal adenocarcinoma: People who are overweight or obese are about twice as likely as normal-weight people to develop a type of esophageal cancer called esophageal adenocarcinoma, and people who are extremely obese are more than four times as likely (9).
- Gastric cardia cancer: People who are obese are nearly twice as likely as normal-weight people to develop cancer in the upper part of the stomach, that is, the part that is closest to the esophagus (10).
- Liver cancer: People who are overweight or obese are up to twice as likely as normal-weight people to develop liver cancer. The association between overweight/obesity and liver cancer is stronger in men than women (11, 12).
- Kidney cancer: People who are overweight or obese are nearly twice as likely as normal-weight people to develop renal cell cancer, the most common form of kidney cancer (13). The association of renal cell cancer with obesity is independent of its association with high blood pressure, a known risk factor for kidney cancer (14).
- Multiple myeloma: Compared with normal-weight individuals, overweight and obese individuals have a slight (10% to 20%) increase in the risk of developing multiple myeloma (15).
- Meningioma: The risk of this slow-growing brain tumor that arises in the membranes surrounding the brain and the spinal cord is increased by about 50% in people who are obese and about 20% in people who are overweight (16).
- Pancreatic cancer: People who are overweight or obese are about 1.5 times as likely to develop pancreatic cancer as normal-weight people (17).
- Colorectal cancer: People who are obese are slightly (about 30%) more likely to develop colorectal cancer than normal-weight people (18).A higher BMI is associated with increased risks of colon and rectal cancers in both men and in women, but the increases are higher in men than in women (18).
- Gallbladder cancer: Compared with normal-weight people, people who are overweight have a slight (about 20%) increase in risk of gallbladder cancer, and people who are obese have a 60% increase in risk of gallbladder cancer (19, 20). The risk increase is greater in women than men.
- Breast cancer: Many studies have shown that, in postmenopausal women, a higher BMI is associated with a modest increase in risk of breast cancer. For example, a 5-unit increase in BMI is associated with a 12% increase in risk (21). Among postmenopausal women, those who are obese have a 20% to 40% increase in risk of developing breast cancer compared with normal-weight women (22). The higher risks are seen mainly in women who have never used menopausal hormone therapy and for tumors that express hormone receptors. Obesity is also a risk factor for breast cancer in men (23).In premenopausal women, by contrast, overweight and obesity have been found to be associated with a 20% decreased risk of breast tumors that express hormone receptors (22).
- Ovarian cancer: Higher BMI is associated with a slight increase in the risk of ovarian cancer, particularly in women who have never used menopausal hormone therapy (24). For example, a 5-unit increase in BMI is associated with a 10% increase in risk among women who have never used menopausal hormone therapy (24).
- Thyroid cancer: Higher BMI (specifically, a 5-unit increase in BMI) is associated with a slight (10%) increase in the risk of thyroid cancer (25).
From a New England Journal of Medicine online study release:
The findings from our approach suggest with high predictive accuracy that by 2030 nearly 1 in 2 adults will have obesity (48.9%; 95% confidence interval [CI], 47.7 to 50.1), and the prevalence will be higher than 50% in 29 states and not below 35% in any state.
Nearly 1 in 4 adults is projected to have severe obesity by 2030 (24.2%; 95% CI, 22.9 to 25.5), and the prevalence will be higher than 25% in 25 states. We predict that, nationally, severe obesity is likely to become the most common BMI category among women (27.6%; 95% CI, 26.1 to 29.2), non-Hispanic black adults (31.7%; 95% CI, 29.9 to 33.4), and low-income adults (31.7%; 95% CI, 30.2 to 33.2).
Although severe obesity was once a rare condition, our findings suggest that it will soon be the most common BMI category in the patient populations of many health care providers. Given that health professionals are often poorly prepared to treat obesity,27 this impending burden of severe obesity and associated medical complications has implications for medical practice and education.
In addition to the profound health effects, such as increased rates of chronic disease and negative consequences on life expectancy,25,28 the effect of weight stigma29 may have far-reaching implications for socioeconomic disparities as severe obesity becomes the most common BMI category among low-income adults in nearly every state.