More Leisure Activity Reduces Risk of Obesity-related Cancers

Moderate to vigorous leisure-time physical activity reduces the risk of all obesity-related cancers compared with light or no activity in both normal weight and overweight individuals, a recent analysis indicates.

Greater levels of physical activity were also associated with lower risks of several individual cancers, including renal cell cancer and colon cancer.

However, the greatest risk reduction occurred in individuals with both higher physical activity levels and lower body mass indexes (BMIs).

"Collectively, these findings underscore the importance of [physical activity] in the prevention of obesity-related cancer irrespective of an individual's body weight," Ming Sun, Department of Clinical Sciences, Lund University, Sweden, and colleagues write. Still, "the greatest risk reduction occurred in the presence of both high physical activity and normal weight."

The study was published online April 1 in the International Journal of Cancer.

Previous research indicates that being physically active reduces a person's risk of certain obesity-related cancers. But whether greater activity and lower body weight act together to prevent cancer remains unclear.

In the study, investigators examined the impact of leisure-time physical activity on obesity-related cancers as well as the combined effect of activity and BMI (< 25 and ≥ 25 kg/m2) on cancer risk in 570,021 individuals from five Scandinavian cohorts. On average, patients were followed for 20 years.

Participants reported the intensity of their leisure-time physical activities, selecting one of five categories on the frequency of exercising to increase their fitness or wellbeing — (1) never, (2) once in a while, (3) one to two times a week, (4) two to three times a week, and (5) more than three times a week —  as well as the minutes spent per week on 17 activities, each of which was assigned a metabolic equivalent of task (MET).

Overall, 19% of people engaged in moderate to high levels of physical activity, and about 54% had a BMI within the low-to-normal range. When combining factors, 11% of participants had low BMI and high physical activity, 8% had high BMI and physical activity, 38% had high BMI and low physical activity, and 43% had low BMI and physical activity.

The authors found that high levels of leisure-time physical activity were associated with a 7% lower risk of any obesity-related cancer compared with low physical activity. Similar associations were observed among participants with low BMIs (6%) and high BMIs (7%).

Higher physical activity was also associated with lower risks of specific cancers, including renal cell (11%) and colon cancer (9%).

When combining high physical activity and low BMI, the relative risk reduction for all obesity-related cancers became most pronounced — with a 24% lower risk compared to those with low physical activity and high BMI. The risk reduction associated with high physical activity and low BMI was most dramatic for endometrial cancer (47%), followed by renal cell cancer (39%), colon cancer (27%), multiple myeloma (23%), and pancreatic cancer (21%).

Although higher physical activity and low-to-normal weight together were associated with a reduced risk of cancer, the authors found no evidence of an interaction between these factors. In other words, high leisure-time physical activity and normal weight appeared to be individually associated with reduced obesity-related cancer risk.

Overall, the results "highlight the importance of physical activity in obesity-related cancer prevention," the authors conclude.

The authors declared no conflicts of interest.

International Journal of Cancer. Published online April 1, 2022. Full text.

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