Research clearly shows that obesity increases the risk of many cancers, including colorectal, postmenopausal breast and ovarian. Now a study published today finds that eating a diet likely packed with added sugar and fat — one relatively high in energy density — increases cancer risk among women only at a healthy weight.
The study was published in the Journal of the Academy of Nutrition and Dietetics. Previous research suggests that poor diets link with overweight and obesity so this study’s results were unexpected to the authors, yet it is one study that needs further research.
“This study’s findings add to the research on how dietary patterns affect cancer risk independent of weight,” said Alice Bender, MS, RDN, AICR Director of Nutrition Programs.
“It’s interesting data that needs more research but what is known now is clear: aside from not smoking, staying a healthy weight is the single most important thing you can do to reduce cancer risk. And eating a diet filled with fruits, vegetables, whole grains and other plant foods – which are low energy density – can support weight management efforts. They also are packed with nutrients and other health-promoting substances that help lower cancer risk.”
Cancer prevention expert Anne McTiernan, MD, PhD., of the Fred Hutchinson Cancer Research Center agrees the study findings are interesting. “It suggests that ‘normal’ is not the same as ‘optimal’,” she said. “So while we say that people with body mass index (weight corrected for height) between 18.5 and 24.9 are ‘normal weight,’ many people in that range could have high amounts of body fat which can fuel initiation or growth of cancers.”
“Eating a diet filled with fruits, vegetables, whole grains and other plant foods – which are low energy density – can support weight management efforts. They also are packed with nutrients and other health-promoting substances that help lower cancer risk.”
Here, the study focused on the energy density of diets. Energy density is a measure of how many calories are in each gram of food. Foods with lower energy density give you less calories in each bite and they tend to be filled with water and fiber. Most fruits, vegetables and other plant foods have low energy density. Foods high in added sugar and fats, such as sweets, fried foods and pastries, tend to have high energy density.
Study researchers used data on approximately 92,000 postmenopausal women from the Women’s Health Initiative. The women had answered questions about their overall diet and other lifestyle factors when they entered the study in the mid-1990s. Then the authors determined how many of the women had developed an AICR-linked obesity-related cancer by 2016.
The study found that women who ate the most energy dense diets were 10 percent more likely to develop an obesity-related cancer compared to those who ate the least energy dense diets. This link appeared independent of body mass index with the increased risk limited to women who were of a normal weight at enrollment.
Although restricting energy dense foods plays a role in weight management, the study found that weight gain was not solely responsible for the rise in cancer risk among normal weight women in the study. They hypothesize that the higher energy dense diets in normal-weight women may cause high insulin levels or other metabolic changes independent of weight that link to cancer risk. Larger waist size – even among normal weight women – may also play a role.
“These findings on dietary energy density suggest that diet is key to cancer risk…. even people in ‘normal’ ranges of weight may benefit from making further changes to lifestyle.”
This study’s calculation of energy density in the diet did not include any beverages, including water. The women also may not have accurately reported their diets.
“These findings on dietary energy density suggest that diet is key to cancer risk,” says McTiernan, also the author of Starved: A Nutrition Doctor’s Journey from Empty to Full. “Our own research shows that physical activity reduces risk for cancer for most people regardless of weight. Therefore, even people in ‘normal’ ranges of weight may benefit from making further changes to lifestyle.”
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