Why Obesity Is Linked to Higher Cancer Rates in Young People

The rates of certain cancers are climbing in young U.S. adults, and it’s not entirely clear why. To make sense of the trend, many scientists are drawing connections to the simultaneous rise of another major public health crisis: obesity.

Younger generations are more likely to develop obesity than ever before. In 2009, about 33% of adults ages 20 to 44 had obesity. By 2020, that number shot up to 41%.1
Having overweight or obesity—a body mass index (BMI) greater than 25—is linked with a higher risk of 13 types of cancer, which account for 40% of cancers diagnosed in the U.S. each year, according to the CDC.2
Scientists have long known that obesity raises the risk of developing and dying of cancer in older adults. More recent research suggests that obesity may also shift the timing of cancer appearance, making it more likely to appear in younger groups.3

The biological mechanisms are complex—fat tissue itself can encourage cancer to develop and grow by spurring inflammation and cancer-promoting hormones.
Obesity is also related to several chronic conditions, like type 2 diabetes and heart disease, which can exacerbate cancer risk.
The 13 types of cancers that are linked to obesity: adenocarcinoma of the esophagus, breast cancer in post-menopausal women, colorectal cancer, uterine cancer, gallbladder cancer, upper stomach cancer, kidney cancer, liver cancer, ovarian cancer, pancreatic cancer, thyroid cancer, meningioma, and multiple myeloma.

How Does Excess Fat Tissue Contribute to Cancer Growth?
Fat tissue isn’t a single idle organ that only stores energy. Rather, there are several types of fat, each of which produce substances that act like hormones, helping to control metabolism by ushering messages between the fat, brain, immune system, and other organs.

Obesity is commonly defined as the accumulation of too much fat. With excess fat tissue comes an excess of a particular group of proteins called adipokines
Adipokines incite inflammation in the fat tissue and sometimes throughout the body. That inflammation can cause cells to mutate and grow quickly, sometimes causing cancer to develop or grow faster.6
How Much Should You Care About Inflammation?

Obesity-induced inflammation also leads the body to produce too much insulin. Apart from contributing to obesity, too-high levels of insulin can encourage cells to grow faster and prevent them from their normal process of death and regeneration. This provides more opportunity for mutations that could lead to cancer.
High insulin is linked to breast, prostate, and colorectal cancers—some of the cancer types that are becoming increasingly common in young adults.
How Does Obesity Complicate Cancer Screening?

Obesity can not only make someone biologically vulnerable to cancer, but may also make it harder to find and treat the disease early on.
In one review paper, some physicians reported lacking the education and tools to effectively perform certain cancer screenings. Patients with obesity, meanwhile, said that factors including embarrassment and experience of previous stigma from healthcare providers stopped them from seeking cancer screening.8

“That [stigma] can make people less willing to come in for screening, particularly screenings where they’re going to have to undress or unclothe in some way, which is most cancer screenings,” Basen-Engquist said.
When people with obesity face barriers to effective screening, early-stage cancers can fly under the radar, sometimes leading them to progress to more aggressive malignancies.
Providers may need to use special techniques during manual cancer exams in people with obesity, like when palpating larger breasts or performing a rectal exam. Obesity can complicate blood tests, too. People with higher weight tend to have a greater volume of blood, which can dilute the levels of proteins that indicate the presence of certain cancer types.