A new study suggests that foods with higher dietary energy density - usually processed foods - may increase the risk of obesity-related cancers in women who are postmenopausal, even if they are actually physically fit.

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Energy-dense foods, such as those that are processed, are linked with an increased risk of cancer in postmenopausal women, regardless of their body weight, new research suggests.

Excess weight is often linked with additional severe disorders, including 13 different types of cancer, among which are endometrial cancer, kidney cancer, cancer of the liver, and pancreatic cancer.

It is also a well-established notion that postmenopausal breast cancer is associated with obesity.

This connection led researchers from the University of Arizona Mel and Enid Zuckerman College of Public Health in Tucson to focus their efforts on studying which dietary practices are liable to lead to cancers in postmenopausal women.

Surprisingly, they found that what might place some older women at risk of obesity-related cancers is not their body weight, but the quality of their nutrition. The findings have been published in the latest issue of the Journal of the Academy of Nutrition and Dietetics.

The researchers observed that dietary energy density (DED), which reflects the quality of someone's nutrition, is what correlates with the risk of cancer in women, even when those women are otherwise physically fit.

"The demonstrated effect in normal-weight women in relation to risk for obesity-related cancers is novel and contrary to our [initial] hypothesis."

Lead investigator Dr. Cynthia A. Thomson, University of Arizona in Tucson

DED measures diet quality by looking at the ratio of calories, or energy consumed, in relation to the nutrients received from a particular food.

For example, processed foods such as pizza and various sugary desserts have a high energy density as they have a lot of calories but are not very rich in nutrients, meaning that a person must consume higher quantities of these foods to get the essentials they need.

Conversely, whole foods such as fruits and vegetables tend to have lower energy density levels, meaning that they contain fewer calories, and they are more nutritious.

DED is calculated by dividing the number of calories in a food serving by its total weight.

Link between diet quality and cancer risk

Dr. Thomson and her colleagues analyzed data collected from a cohort of 90,000 postmenopausal women who participated in the Women's Health Initiative. To determine the impact of DED on cancer risk for the participants, the researchers asked them to fill in a food frequency questionnaire.

In this way, they were able to collect data on the participants' dietary habits, including their estimated energy intake, and the nutrient quality of the foods they consumed.

The weights of all the foods were taken from the United States Department of Agriculture database, allowing the researchers to calculate DED.

As for the participants' cancer outcomes, Dr. Thomson explains that this information was obtained from the women's medical records and was reviewed by specialists to confirm the diagnoses.

It was found that postmenopausal women on high DED diets had a 10 percent higher risk of developing a form of obesity-related cancer. This result was, surprisingly, limited to participants who reported a normal body weight at baseline.

"Among normal-weight women, higher DED may be a contributing factor for obesity-related cancers. Importantly, DED is a modifiable risk factor. Nutrition interventions targeting energy density as well as other diet-related cancer preventive approaches are warranted to reduce cancer burden among postmenopausal women," suggests Dr. Thomson.

Women should mind nutritional value

The researchers advise that older women should consume fewer foods with high energy density in order to help prevent the risk of cancer. However, Dr. Thomson and her colleagues also acknowledge that DED, as such, may not be the direct cause of cancer risk.

In fact, the study advances the hypothesis that high DED may affect the women's metabolisms, leading to dysregulations, which are a known factor in susceptibility to cancer.

Dr. Thomson suggests that future studies should aim to test whether the same link between DED and obesity-related cancer risk also holds true for younger women or men.

In the meantime, the researchers urge women to be mindful of the quality of their diets, regardless of their physical weight.