Dieting may reduce cancer risk in overweight, obese postmenopausal women

In obese, overweight, and sedentary postmenopausal women, simple lifestyle changes—such as a calorie-restrictive diet with or without exercise—may be all it takes to lower their risks of cancer, concluded researchers. In a recent study, they found that in these women, caloric-restriction and weight loss reduced several biomarkers of inflammation, which is hypothesized to be the mechanism by which their risk for cancer is increased, according to research published in the journal Cancer Research (2016;72(9):2314-2326).

“We know that being overweight and having a sedentary lifestyle is associated with an increase in risk for developing certain types of cancer. However, we don’t know exactly why,” said co-author of the study, Catherine Duggan, PhD, principal staff scientist, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA.

“We wanted to investigate how levels of some biomarkers associated with angiogenesis were altered when overweight, sedentary, postmenopausal women enrolled in a research study lost weight and/or became physically active over the course of a year,” she explained.

To do this, Dr. Duggan and colleagues enrolled 439 overweight/obese women aged 50 to 75 years, who were healthy, postmenopausal, and sedentary, and randomly assigned them to one of four study arms to measure the effects of exercise and diet on circulating levels of high-sensitivity C-reactive protein (hs-CRP), serum amyloid A (SAA), interleukin-6 (IL-6), leukocyte, and neutrophil levels after 1 year. These four arms were comprised of the following:

• A calorie-restricted arm, with no more than 2,000 kcal/day including less than 30% fat, and a goal of 10% weight loss (n=118);
• An aerobic exercise arm, with a minimum of 225 min/week moderate to vigorous exercise (n=117);
• A combined diet and exercise arm (n=117); and
• A control arm, with no intervention (n=87).

At baseline and at 12 months, researchers measured hs-CRP, SAA, IL-6, leukocyte, and neutrophil levels, and—after adjusting for baseline body mass index (BMI), race/ethnicity, and age—found that women in the diet and the diet + exercise groups had significantly lower levels of all of these proteins compared with controls:

• Hs-CRP decreased by geometric mean: 0.92 mg/L (95% CI: 0.53-1.31; P < 0.001) in the diet group; and by 0.87 mg/L (95% CI: 0.51-1.23; P < 0.0001) in the diet + exercise groups.
• IL-6 decreased by 0.34 pg/mL (95% CI: 0.13-0.55; P=0.001) in the diet group, and by 0.32 pg/mL (95% CI: 0.15-0.49; P < 0.001) in the diet + exercise groups.
• Neutrophil counts decreased by 0.31x109/L (95% CI: 0.09-0.54; P=0.006) in the diet group, and by 0.30x109/L (95% CI: 0.09-0.50; P=0.005) in the diet + exercise groups.

Importantly, they also found that compared with controls, those in the diet and the diet + exercise groups who had reduced their weight by 5% or more also reduced their levels of hs-CRP, SAA, and IL-6. Furthermore, in all subgroups of baseline BMI, waist circumference, CRP levels, and fasting glucose, women in the diet and the diet+exercise groups reduced hs-CRP.

Women in the exercise-only arm did not demonstrate these lower levels, however. Finally, Dr. Duggan and colleagues found that the greater the weight loss, the greater the reductions in these serum angiogenesis-related protein levels.

“Our study shows that weight loss is a safe and effective method of improving the angiogenic profile in healthy individuals. We were surprised by the magnitude of change in these biomarkers with weight loss. While we can’t say for certain that reducing the circulating levels of angiogenic factors through weight loss would impact the growth of tumors, it is possible that they might be associated with a less favorable milieu for tumor growth and proliferation,” Dr. Duggan said.

She added a caveat, however, in that only three angiogenic factors were measured, although there are several others; in addition, the biomarkers were measured only in circulating blood rather than in adipose or other tissues.

Nevertheless, their results were clear.

“Exercise is important for helping to prevent weight gain, and to maintain weight loss, but does not cause a large amount of weight loss on its own. Our study shows that making lifestyle changes—in this case simple changes to the diet to reduce weight—can lower the risk factors for cancer,” concluded Dr. Duggan.

This study was funded by the National Cancer Institute and the Breast Cancer Research Foundation.