High Amounts of Visceral Fat Linked to an Increased Risk for Colon Cancer

Visceral fat or fat stored in the abdominal cavity has been directly linked to an increased risk for colon cancer, according to data from a mouse study published in Cancer Prevention Research, a journal of the American Association for Cancer Research.

"There has been some skepticism as to whether obesity per se is a bona fide cancer risk factor, rather than the habits that fuel it, including a poor diet and a sedentary lifestyle," said Derek M. Huffman, Ph.D., postdoctoral fellow at the Institute for Aging Research at the Albert Einstein College of Medicine in Bronx, N.Y. "Although those other lifestyle choices play a role, this study unequivocally demonstrates that visceral adiposity is causally linked to intestinal cancer."

Prior research indicates that obesity markedly increases the likelihood of being diagnosed with and dying from many cancers. Researchers were hoping to determine if removing visceral fat in mice genetically prone to developing colon cancer might prevent or lessen the development of these tumors.

They randomly assigned the mice to one of three groups: the first group of mice went through a fake surgery and were allowed to eat whatever they liked throughout the study, the second group was also provided with an unrestricted diet, and the third group also underwent a sham surgery but were only provided 60 percent of the calories of the other mice.

"Our sham-operated obese mice had the most visceral fat, developed the greatest number of intestinal tumors, and had the worst overall survival," Huffman said. "However, mice that had less visceral fat, either by surgical removal or a calorie-restricted diet, had a reduction in the number of intestinal tumors. This was particularly remarkable in the case of our group where visceral fat was surgically removed, because these mice were still obese, they just had very little abdominal fat."

Researchers concluded that in female mice, the removal of visceral fat was significantly related to a reduction in intestinal tumors, but calorie restriction was not, and in male mice, calorie restriction had a significant effect on intestinal tumors, but removal of visceral fat did not.

"This suggests that there are important gender differences in how adiposity and nutrients interact with the tumor environment," Huffman said. "In addition, the study emphasizes the need to promote strategies that reduce visceral fat in abdominally obese individuals."

Huffman noted that more studies are needed to definitively uncover the mechanisms behind the causality between visceral fat and intestinal cancer, to determine how abdominal obesity and nutrient availability act independently during the stages of tumor promotion and progression, and to determine how other strategies to promote weight loss, such as bariatric surgery, affect cancer risk.