Excess Weight, Not Diet, Triggers Colon Cancer

Being overweight puts people at risk of colon cancer, a new study suggests. Researchers found that obesity, rather than diet, leads to changes in the colon that can cause colorectal cancer. 

Researchers said the latest findings strengthens that idea that guidelines on healthy diets and frequent exercise can significantly reduce the risk of colon cancer, which is the second leading cause of cancer-related death in the United States.

Many studies have found that obese people are significantly more likely to get colorectal cancer. Researchers sought to gain deeper understanding of the mechanism behind this link by feeding two groups of mice a diet in which 60 percent of the calories came from lard.

Researchers said the first group of mice had a human version of a gene called NAG-1, which has previously been shown to protect against colon cancer. However, the second group did not have the NAG-1 gene.

The findings revealed that mice with the NAG-1 gene did not gain weight after eating the high-fat diet. However, mice without the gene gained significant amounts of weight after eating a fatty diet.

The findings also found that obese mice were more likely to have molecular signals in their guts that can lead to cancer.

"The obese mice exhibited molecular signals in their gut that led to the progression of cancer, but the NAG-1 mice didn't have those same indicators," co-researcher Thomas Eling, Ph.D., a scientist at the National Institute of Environmental Health Sciences (NIEHS) said in a news release.

Researchers found that the acetylation patterns for the obese mice and the thin NAG-1 mice were radically different. Researchers explained that obese mice showed patterns that resembled those from mice with colorectal cancer. Having excess weight also seemed to activate more genes associated with colorectal cancer progression, suggesting the obese mice are susceptible to colon cancer.

"Any preexisting colon lesions in these animals are more likely to evolve rapidly into malignant tumors," researcher Paul Wade, Ph.D., of the National Institute of Environmental Health Sciences said in a statement. "The same thing may happen in humans."

"Once we identify the signaling pathways and understand how the signal is transduced, we may be able to design ways to treat colorectal cancer in obese patients," Wade added.

Researchers said the next step is to find out how obesity triggers the body to develop colorectal cancer. While the likely scapegoats for trigger tumor growth in the color are fat cells, researchers said there are many more possibilities. Eling and Wade believe that the discovery of these cellular switches will help researchers create drugs that will protect people from colorectal cancer.

The findings are published in the journal Cell Metabolism.