Overweight women who shed just 5 percent of their body fat may be able to make a dent in their cancer risk, according to a new study.
Women who restricted their calories and exercised regularly experienced an almost 42 percent reduction of C-reactive protein. Levels of that protein rise when there is inflammation in the body. Interleukin-6, a protein the body makes to help regulate immune function, decreased by just over 24 percent.
Being overweight or obese is linked with increased risk of many cancers; an estimated 1 out of every 3 cancer deaths in the U.S. is linked to excess weight or inactivity. Many experts believe that inflammation is one possible underlying mechanism.
"We think that the inflammation produced in fat tissue and released into the bloodstream might be, in part, responsible for the consistent associations seen between obesity and cancer," said co-author Dr. Anne McTiernan, director of the Prevention Center at the Fred Hutchinson Cancer Research Center.
"Our study shows that a lifestyle change program that is relatively easy for most people to adopt can markedly reduce these blood inflammation markers," she continued.
For the new study, published in the journal Cancer Research on Tuesday, researchers recruited more than 400 overweight or obese postmenopausal women. They split participants into three groups -- one went on a reduced calorie diet, one exercised for 225 minutes per week and one tried a combination of diet and exercise. (The researchers also had a control group.)
Overall, women in the diet and exercise group saw the biggest reduction in biomarkers of inflammation. They were followed by the diet group, which also saw substantial changes.
But women who only exercised saw little effect on their inflammation markers.
"I think the main issue is body fat," McTiernan said. "The more fat one has, the more inflammation-producing cells there are, and therefore more inflammation markers produced and sent into the bloodstream." The diet and exercise group likely saw the biggest change simply because exercise is an important part of weight loss, she explained.
One question the new study raises is if any particular diet leads to greater inflammation marker changes than others. That question would be tackled in future research, McTiernan said, but in the current study, women assigned to the weight loss groups ate a diet low in calories and fat, while increasing their fruit and vegetable consumption.
And there is no standard, magic amount established by the new study that people to lose in order to see changes in biomarkers of inflammation. Experts said they are heartened by the fact that even minor weight loss seems to influence risk.
"In general, relatively modest changes in weight can be associated with pretty significant decreases in the risk of developing diseases including, potentially, cancer," said Dr. Jennifer Ligibel, a medical oncologist in the women's cancer's program at the Dana-Farber Cancer Institute.
Indeed, the women in the new study, who were overweight or obese, did not need to get down to what would be considered a healthy weight in order to see changes in their biomarkers of inflammation. (A healthy body mass index, a measurement of weight relative to height, is 18.5 to 24.9.)
This may be welcome news for the 1 in 3 adults in the U.S. who are considered obese.
But Ligibel cautioned that the new research only looks at inflammation and not about the direct risk of developing cancer or having it recur. Groups such as the American Cancer Society state that the links between body weight and cancer risk are not yet fully understood."Data like this tells us a little about what happens biologically," Ligibel said. "The next step is a big one. It's looking to see whether these interventions make a difference not just in blood markers, but in the risk of developing cancer and having it come back."