Our study supports the growing evidence that early-life body size can influence risk of colorectal cancer many decades later.
—Esther K. Wei, ScD
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 by Xuehong Zhang, MD, ScD, Instructor at Harvard Medical School, and colleagues in Cancer Epidemiology, Biomarkers & Prevention.1
“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, Scientist 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.”
Researchers pulled data from two large and long-term cohorts: 75,238 women who were part of the Nurses’ Health Study, and 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.
During 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% higher risk of colorectal cancer compared to those who were most lean at those ages. Women who were overweight as adolescents had a 27% 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, said Dr. Wei. “We really don’t know why we only observed the association 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.”
Disentangling the independent link between being overweight as a youth and as an adult is challenging. For adults, there is a clear link between being obese and increased risk of colorectal cancer as well as many other cancers. Excess body fat can cause high levels of insulin and insulin-like hormones, which may fuel colorectal cancer.
The role of excess body fat and cancer risk over a lifetime is an emerging and important area of research. Approximately a third of children and adolescents are overweight or obese, according to the Centers for Disease Control and Prevention. ■
1. Zhang X, et al: Cancer Epidemiol Biomarkers Prev 24:690-697, 2015.