How Does Obesity Increase Cancer Risk?

Researchers zero in on the cancer-causing properties of excess abdominal fat.

While many researchers have found that obesity is a major driver of certain cancers, the underlying drivers of this relationship have not been well-understood.

Findings from a new study published by Oncogene suggest that a protein released from fat can turn healthy cells cancerous.

The authors hypothesize that fat housed further under the skin is likely the cause of this relationship, as it releases more of the protein that causes cancer growth compared with more superficial fat.

“While there have been several advances in treating cancer and improving the quality of life of patients, the number of new cases continues to surge,” said lead study author Jamie Bernard, PhD. “It’s important to understand the cause so we can do a better job at reducing the number of cancer cases using dietary modifications or therapeutic interventions.”

Approximately one-third of Americans are obese, putting them at higher risk of breast, colon, prostate, uterine, and kidney cancers. These new findings suggest that obesity alone may not be the best predictor of cancer risk.

“Our study suggests that body mass index, or BMI, may not be the best indicator,” Dr Bernard said. “It’s abdominal obesity, and even more specifically, levels of a protein called fibroblast growth factor-2 [FGF2] that may be a better indicator of the risk of cells becoming cancerous.”

Subcutaneous fat is the top layer of fat and lies right under the skin, while visceral fat is found under the other type of fat. Based on their findings, the authors believe that visceral fat may promote cancer.

The investigators found that mice fed a high-fat diet had visceral fat that produced increased amounts of FGF2 compared with subcutaneous fat, according to the study. FGF2 was found to stimulate vulnerable cells and caused them to turn cancerous.

The authors also examined fat samples from women undergoing hysterectomies and discovered similar findings. In humans, when fat secretions had heightened levels of the FGF2 protein, more cells became cancerous when transferred to mice, according to the study.

“This would indicate that fat from both mice and humans can make a non-tumorigenic cell malignantly transform into a tumorigenic cell,” Dr Bernard said.

The authors reported that other factors released from fat, such as estrogen, may impact cancer risk; however, no studies have shown a direct cause. Genetics are also thought to play a role in abdominal fat and cancer risk.

The investigators are currently searching for novel anti-cancer drugs that may inhibit the effects of FGF2, according to the study.

“There’s always an element of chance in whether a person will get cancer or not,” Dr Bernard said. “But by making smarter choices when it comes to diet and exercise and avoiding harmful habits like smoking, people can always help skew the odds in their favor.”