A low-calorie, low-fat diet, with or without exercise, could reduce the risk of cancer in women by lowering levels of oxidative stress, according to researchers from the University of Washington School of Public Health and Fred Hutchinson Cancer Research Center.

Women who changed their diets to reduced calorie and reduced fat—with a goal of losing 10 percent of their starting weight over one year—significantly reduced markers of oxidative stress, an imbalance in the body’s ability to defend itself against the damaging action of free radicals.

Oxidative stress is a relatively unexplored mechanism that could link obesity with cancer risk.

“We think that oxidative stress could damage DNA and begin the process of carcinogenesis, or cancer formation,” said Anne McTiernan, a research professor of epidemiology at the School and member of the Public Health Sciences Division at Fred Hutch. “The findings from our study suggest that it’s never too late to make lifestyle changes to lower risk for cancer.”

McTiernan and the research team investigated the effects of diet and exercise on markers of oxidative stress, including F₂-isoprostanes, oxidized low-density lipoprotein and fluorescent oxidation products. The results were published online in Cancer Prevention Research.

The team enrolled 439 postmenopausal women, ages 50 to 75 years, who were either overweight or obese. Participants were randomly assigned to one of four groups for a 12-month period: diet, exercise, diet and exercise, and control.

Compared to the control group, women in the diet and diet and exercise groups had reduced F₂-isoprostanes by 23 and 24 percent, respectively. However, F₂-isoprostanes were not significantly reduced for women in the exercise group. F₂-isoprostanes are a series of compounds produced by the reaction of free radicals with arachidonic acid. They are considered the gold-standard test for measuring oxidative stress in vivo.

“Women on diets also had lowered levels of oxidized low-density lipoprotein and increased levels of fluorescent oxidation products,” McTiernan said. “Our trials support further pathways through which obesity and sedentary lifestyles could increase risk of several cancers.”

Catherine Duggan, Jean de Dieu Tapsoba, Ching-Yun Wang, Kristin L. Campbell, Karen Foster-Schubert and Myron D. Gross were part of the research team.