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Weight loss reduces cancer risk in overweight women

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Overweight or obese women who lose at least 5 percent of their body weight may lower their levels of the type of inflammation linked with cancer, according to a new study.

The findings show that women who dieted, exercised and lost weight saw their levels of an inflammation marker called C-reactive protein drop by 42 percent, and lowered their levels of another inflammation marker linked to cancer, called interleukin-6, by 23 percent over the course of a year.  

"Both obesity and inflammation have been shown to be related to several types of cancer," said study researcher Dr. Anne McTiernan, of the Fred Hutchinson Cancer Research Center in Seattle. Studies have linked obesity to an increased risk of cancers of the endometrium, colon, pancreas and kidney. Development of as many as 25 percent of cancers is likely facilitated by a sedentary lifestyle and higher-than-normal body weight, McTiernan said.

The decreases in inflammation seen in the study were larger than anti-inflammatory medications would produce, McTiernan said. Researchers believe that inflammation damages tissues and organs in the body — damage that can result in cancer development, or the progression of existing cancer, she said.

The findings "reinforce the importance of weight control on biomarkers that not only have strong associations with cancer, but also with other prevalent chronic diseases, such as cardiovascular disease," said Wendy Demark-Wahnefried, of the University of Alabama Comprehensive Cancer Center in Birmingham, who was not involved in the study.  

The study is published today (May 1) in the journal Cancer Research.

Cancer and weight loss

The study looked at 439 overweight and obese post-menopausal women. The women were assigned, for one year, to either a calorie-restricted diet, exercise, or both. The goal for each participant was to reduce their body weight by 10 percent. The researchers ran blood tests to measure the women's levels of inflammation markers.

Women who dieted, but were not assigned to exercise, saw drops in inflammation similar to those of the women who dieted and did exercise, the findings showed.

But exercise alone did not affect inflammation levels — a finding that did not surprise McTiernan. Previous studies showed that exercise only reduced inflammation if the person lost a significant amount of weight, she said.  

It seems to be that the loss of fat is the critical issue, she said.

Dr. Tim Byers, associate director for Cancer Prevention and Control at the University of Colorado Cancer Center, agreed. "It’s really not surprising that body weight and the amount of weight loss determines the changes in these circulating inflammatory factors," he said.

However, while higher levels of inflammation are associated with an increased risk for certain cancers, a cause-and-effect link between increased inflammation and cancer has not yet been fully established, the researchers noted. According to experts, other obesity-related factors besides inflammation, such as levels of blood sugar and sex hormones, can also increase cancer risk.

What women can do to lower their cancer risk

McTiernan said that women who are overweight should first stop gaining weight, and then increase their physical activity. "At least 150 minutes or more per week of moderate or vigorous level activity — this is what is in the national guidelines," she said.

Women need to get a handle on what they are really eating, she said. Using an online calorie-counter program or old-fashioned food log should do the trick. "Most women should be taking in less than 2,000 calories per day, unless you're an athlete."

For weight loss, a realistic goal is losing one to two pounds a week, and to aim for a 10 percent reduction over a six-month period, McTiernan said.

Large benefits can be expected with even small amounts of weight loss, Byers said. He advised keeping up with exercise to maintain a normal body weight.

Both Byers and Demark-Wahnefried said the results of the study are not restricted to postmenopausal women. "The current data suggest that maintaining a healthy weight over the entire life course is important, regardless of gender," Demark-Wahnefried said.

Pass it on: Losing weight can lower levels of harmful inflammation, and could decrease cancer risk.

 

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