Girls who are overweight as young children and teens may face increased risk for colorectal cancer decades later, regardless of what they weigh as adults, suggests a new study published in Cancer Epidemiology Biomarkers and Prevention.
The study is partially funded by the American Institute for Cancer Research.
"Our study supports the growing evidence that early-life body size can influence risk of colorectal cancer many decades later," said senior study author Esther K. Wei, ScD, at the California Pacific Medical Center. "Although we don't need any additional evidence to encourage obesity prevention and increased physical activity in children, this study adds additional imperative to prioritizing children's health."
For the study, researchers pulled data from two large and long-term cohorts: One included 75,238 women who were part of the Nurses' Health Study; The other included 34,533 men from the Health Professionals Follow-up study.
In 1988, participants were presented with a set of nine diagrams of body shapes, ranging from the most slender to the most overweight. Participants selected what his or her body shape looked like at ages 5, 10, 20, 30, and 40, along with their current age. Then everyone regularly answered questionnaires about their weight, activity, diet and other lifestyle habits.
After an average of 22 years, 2,100 people had developed colorectal cancer. After adjusting for adult weight, the researchers found that women who were overweight as young children had a 28 percent higher risk of colorectal cancer compared to those who were most lean at those ages. Women who were overweight as adolescents had a 27 percent increased risk.
Unexpectedly, the same link for overweight boys and adult colorectal cancer was not found.
Not seeing the similar link among men could be due to faulty recall, chance, or unknown biology, says Wei. "We really don't know why we only observed the associated in women and not in men, but since this is still a relatively new area of research, it's too early to conclude that this association does not exist in men," said Wei.
While the link between obese adults and higher risk of colorectal cancer is clear – for both women and men – the role of excess body fat over the life-course is an emerging area of research.
Disentangling the independent link between being overweight and youth and as an adult is challenging, note the authors. But this study does confirm previous research. Excess body fat can cause high levels of insulin and insulin-like hormones, which studies suggest increases risk of colorectal cancer.
The study was supported by the American Institute for Cancer Research and National Institutes of Health.
Source: Source:Zhang X, Wu K, Giovannucci EL, Ma J, Colditz GA, Fuchs CS, Willett WC, Stampfer MJ, Nimptsch K, Ogino S, Wei EK. "Early Life Body Fatness and Risk of Colorectal Cancer in U.S. Women and Men-Results from Two Large Cohort Studies.' Cancer Epidemiol Biomarkers Prev. 2015 Mar 16. [Epub ahead of print].
Published on April 6, 2015