Around 150,000 people are diagnosed with colorectal cancer each year in the United States, according to the Cancer Research Institute. Increasingly, those patients are younger adults. Recent reports show that 1 in 5 people diagnosed with colorectal cancer are younger than 55 — roughly double the rate seen in the 1990s. Among adults ages 20 to 39, incidence has been rising by about 2 percent per year since the mid-1990s.

What is triggering the increase in colorectal cancer rates? Experts point to changes in body fat composition, physical activity and nutrition.

Fat composition matters when discussing colon cancer risk. Visceral fat — fat stored deep in the abdomen around internal organs — is more metabolically active than fat under the skin. As fat cells enlarge, they release more pro-inflammatory substances and fewer anti-inflammatory ones, contributing to chronic inflammation. Over time, persistent inflammation can damage cells and increase the risk of cancer development.

Physical inactivity is another concern. Sedentary behavior is associated with higher insulin levels in the blood. Elevated insulin can act as a growth signal, promoting cell proliferation, reducing normal cell death and increasing the activity of insulin-like growth factors. A 2022 study by An Sanghyun published in the Journal of Korean Medicine reported that sedentary individuals without physical activity had about a 30 percent higher risk of colon cancer, while engaging in any type of regular exercise significantly reduced that risk.

Diet also plays a central role. High consumption of red meat has been associated with increased colorectal cancer risk, in part due to inflammation linked to heme iron. Diets low in fiber can disrupt beneficial gut bacteria, reduce production of protective anti-inflammatory compounds and slow intestinal transit time, increasing the colon’s exposure to potential carcinogens.

Ultra-processed foods have also been linked to increased risk. A 2022 study published in The BMJ found that high consumption of ultra-processed foods was associated with a 29 percent increased risk of colorectal cancer. Emerging research is examining environmental exposures as well. A study published in the August 2025 issue of Cancer Epidemiology found higher concentrations of microplastics in colon cancer tissue compared with control samples, suggesting that chronic exposure may contribute to cancer-related changes.

Screening has helped reduce disease in older adults. Since colorectal cancer screening became more common in the mid-1990s, rates among people older than 55 have declined.

In response to rising cases in younger adults, the American Cancer Society updated screening guidelines in 2021 to recommend starting routine screening at age 45 instead of 50.

Screening options include stool-based tests that can be done at home, flexible sigmoidoscopy and colonoscopy. Colonoscopy remains the gold standard in colorectal cancer prevention because of its ability to remove abnormal tissue during the exam.

People with a family history of colorectal cancer, a known genetic predisposition or symptoms such as changes in bowel habits or blood in the stool should discuss earlier evaluation with their physician.

While no single factor explains the rise in colorectal cancer in young adults, many of these risks are modifiable. Managing metabolic syndrome to reduce visceral fat, incorporating physical activity into daily life, prioritizing fiber-rich whole foods, limiting ultra-processed foods and red meat, and keeping up with recommended screening can collectively reduce colorectal cancer risk.