High Fat Diet Linked To Higher Colon Cancer Risk, Early Research Shows

• Researchers say findings from a mouse study indicate that a high fat diet may increase the risk of colon cancer.
• The findings suggest that certain fats can alter intestinal stem cells and potentially lead to tumor development.
• Experts say the study provides valuable information, but more research is needed to verify the effects in humans.

In a new study, researchers report that a high fat diet may potentially increase the risk of colon cancer.

The researchers from Arizona State University said a diet high in certain fats can cause lasting changes in intestinal stem cells that lead to the development of tumors and the possibility of colon cancer.

The study was conducted in mice, but the researchers noted changes in the DNA of intestinal stem cells that may explain their growth and survival.

The researchers published their findings on November 12 in the journal Stem Cell Reports.

The researchers said the study is important because 1 in 25 people develop colon cancer in their lifetime. In the United States, that translates into about 108,000 new cases of colon cancer every year. About 55,000 males and 55,000 females are expected to die from the disease in 2026.

Experts not involved in the study say the research provides valuable information, but they have reservations about the results, as the findings do not yet apply to humans.

“The findings provide a potential mechanism linking diet to intestinal cancer development, but we need to be cautious about translating these results to humans,” said Dalia Perelman, MS, CDE, a research dietitian at Stanford University in California.

“We already have evidence from human studies that obesity and certain dietary patterns, particularly those high in processed meats and low in fiber-rich foods, are associated with increased colorectal cancer risk,” Perelman told Healthline. “This study adds a potentially important mechanism to investigate, but it does not establish that dietary fat itself increases colorectal cancer risk in humans.”

Ketan Thanki, MD, a colorectal surgeon specializing in benign and malignant diseases of the colon, rectum, and anus at the MemorialCare Todd Cancer Institute at Long Beach Medical Center in California, shared similar views.

“This study provides a better understanding at the cellular level of how a high fat diet may contribute to colorectal cancer development,” Thanki told Healthline.

“Animal studies are an important starting point for understanding biological processes, but we must be cautious about directly applying their findings to humans,” he added. “Mice and humans share many cellular and biological mechanisms, which makes these studies valuable in identifying potential pathways involved in disease development. However, human diets, genetics, metabolism, and environmental exposures are more complex.”

How high fat diets might increase colon cancer risk

To reach their findings, the Arizona State researchers fed mice what the scientists described as a Western-style high fat diet for 6 months.

They then compared those results with those from mice given a low fat diet.

The researchers said the mice on the high fat diet gained more weight than the mice on the low-fat diet. They also developed more intestinal stem cells, and those cells grew at a more rapid rate.

They added that mice genetically predisposed to intestinal cancer who were fed a high-fat diet developed more and larger tumors.

The researchers noted changes in the DNA of intestinal stem cells that may help explain their increased growth and survival.

They also pointed out that stem cell behavior returned to normal after high fat diet mice were switched to a low fat diet, although some DNA changes persisted. After four weeks, approximately 18% of these changes remained.

When mice were returned to a high fat diet, the researchers said their intestinal stem cells responded more quickly and strongly than those of mice exposed to the diet for the first time.

They concluded that the study suggests that maintaining a healthy, low fat diet may help regulate intestinal stem cell growth and reduce colon cancer risk.

Kristin Kirkpatrick, RD, president of KAK Consulting and a dietitian at the Cleveland Clinic Department of Wellness & Preventive Medicine in Ohio, wasn’t involved in the study but highlighted a particular aspect of the findings.

“What I found particularly interesting was that even after the mice returned to a low fat diet, some of the molecular changes persisted,” she told Healthline. “This raises questions about how our dietary patterns over time may influence long-term health.”

Experts provide some cautions about study findings

Experts said these new findings are interesting but noted numerous caveats.

“One important takeaway is that dietary habits over time matter,” said Thanki. “Even if someone has consumed a high fat diet for years, making changes now may still provide meaningful health benefits.”

“I also think these findings are particularly important for children and adolescents, as establishing healthier dietary habits early in life may provide long-term benefits,” he added.

However, Thanki noted that not all fats are the same. “The health risks depend partly on the type of fat consumed, how much is consumed, and what foods make up the overall diet,” he said.

“Diets consistently high in saturated fats, particularly those containing large amounts of processed meats, fried foods, and highly processed products, can contribute to obesity, elevated cholesterol, cardiovascular disease, and metabolic dysfunction. These factors can also contribute to chronic inflammation and may increase the risk of certain cancers, including colorectal cancer,” Thanki continued.

Perelman said the diet used in the study was extremely high in fat, providing 60% of calories from fat, primarily from lard.

“We know that the health effects of dietary fats differ depending on their sources and fatty acid composition, and we cannot assume that a diet rich in unsaturated fats from foods such as olive oil, nuts, and seeds would produce the same effects,” she noted.

Perelman added that the researchers primarily studied stem cells from the small intestine rather than the colon.

“Although these tissues share some biological characteristics, they have important differences, and we cannot assume that the same changes would occur in the colon,” she explained.

Finally, Perelman noted that “the mice consuming the high fat diet also gained weight, making it difficult to separate the effects of dietary fat itself from those associated with increased body fat and other metabolic changes.”

How to lower unhealthy fats in your diet

Not all high fat foods are unhealthy. Some high fat foods that offer healthy benefits include:

• avocados
• cheese
• eggs
• fatty fish
• nuts
• full-fat yogurt

“The goal shouldn’t necessarily be to eliminate fat because our bodies need healthy fats for normal functioning,” said Thanki. “Instead, people should focus on reducing saturated and trans fats while incorporating healthier unsaturated fats in appropriate amounts.”

Thanki had several dietary suggestions. Among them:

• Replace fatty cuts of red meat and processed meats with lean proteins such as fish, skinless poultry, beans, and lentils.
• Choose cooking methods such as baking, grilling, steaming, or roasting instead of deep-frying.
• Limit fast food, highly processed snacks, and packaged foods high in saturated fats.
• Use olive oil in place of butter or other sources of saturated fat when cooking.
• Incorporate fiber-rich foods, including vegetables, fruits, whole grains, and legumes.

“Consistency matters more than perfection. Even modest dietary changes, maintained over time, can have meaningful health benefits,” Thanki said.

Perelman agreed. “The overall quality of the diet matters. Diets that are very high in fat may displace other foods and nutrients that have important health benefits,” she said.

“For colorectal cancer specifically, higher intakes of dietary fiber and whole grains have consistently been associated with lower risk,” Perelman noted.

“Therefore, rather than focusing exclusively on reducing fat, it is important to consider the overall dietary pattern and whether it provides adequate amounts of fiber-rich plant foods and other beneficial nutrients.”

Kirkpatrick agreed that the type of fat is what is important. “A Mediterranean-style diet that includes olive oil, nuts, seeds, and fatty fish can be relatively high in fat but is consistently associated with positive health outcomes,” she said. 

“On the other hand, a diet high in saturated fat, processed meats, and ultra-processed foods may increase the risk of certain chronic diseases, particularly when it’s also low in fiber and other protective nutrients.”

Kirkpatrick also noted that many lifestyle habits contribute to a person’s overall health.

“Our health is influenced by so many factors beyond diet, including how we manage stress, our sleep habits, physical activity, genetics, and overall lifestyle,” she said.