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Weight and rectal cancer

Weight in adolescence associated with rectal cancer risk

Obesity, but not overweight, was associated with a risk for rectal cancer among men and women

A study by researchers form Rabin Medical Center and the Tel Aviv University in Israel has uncovered a link between being overweight or obese in adolescence and an increased risk of developing colon cancer in adulthood.

Published in the journal Cancer, a peer-reviewed journal of the American Cancer Society, the findings revealed that obesity was also associated with an elevated risk of developing rectal cancer, and come at a time of growing concern about the impact of adolescent overweight and obesity on chronic disease later in life.

The study, ‘Adolescent body mass index and risk of colon and rectal cancer in a cohort of 1.79 million Israeli men and women: A population-based study’, results on a potential link between adolescent obesity and the risk of colorectal cancer are conflicting, and many of the studies' designs have been limited. To provide more clarity, Professor Zohar and his colleagues analysed information on 1,087,358 Jewish males and 707,212 Jewish females who underwent health examinations, including measures of body mass index (BMI), at age 16 to 19 years (predominantly aged 17 years) between 1967 and 2002. Individuals were followed to 2012.

Cox regression was used to estimate hazard ratios (HRs) for cancer according to age- and sex-adjusted BMI percentiles from the US Centers for Disease Control and Prevention (overweight, 85th percentile to <95th percentile; obesity, ≥95th percentile).

Over a median follow-up of 23 years, 2967 new cases of colorectal cancer were identified, including 1977 among men (1403 colon, 574 rectum) and 990 among women (764 colon, 226 rectum). Overweight and obesity were associated with 53% and 54% higher risks of colon cancer for men and women, respectively. Obesity was associated with a 71% increased risk of rectal cancer in men and more than a twofold increased risk in women.

Over a median follow-up of 23 years, they identified 2,967 incidence cases of colorectal cancer, including 1,977 among men (1,403 in the colon and 574 in the rectum) and 990 among women (764 in the colon and 226 in the rectum).

Overweight and obesity were associated with the risk for colon cancer among both men (HR for overweight, 1.53; 95% confidence interval [CI], 1.28-1.84; HR for obesity, 1.54; 95% CI, 1.15-2.06; statistically significant from a BMI 23.4 kg/m2 [spline analysis]) and women (HR for overweight, 1.54; 95% CI, 1.22-1.93; HR for obesity, 1.51; 95% CI, 0.89-2.57; significant from a BMI 23.6 kg/m2).

Obesity, but not overweight, was associated with a risk for rectal cancer among men (HR, 1.71; 95% CI, 1.11-2.65; significant from a BMI 29.6 kg/m2) and women (HR, 2.03; 95% CI, 0.90-4.58; significant from a BMI 30.6 kg/m2).

Although the researchers acknowledge that the study cohort was still young, with the median age at colorectal cancer diagnosis of 49.4 years, and that the study also lacked data on diet, physical activity, smoking and family history, which might affect risk estimates, they nevertheless concluded that being overweight or obese in adolescence was associated with an increased risk of subsequent colon cancers in men and women, whereas obesity was associated with rectal cancer.

"This is a huge cohort with a minimum follow up of ten years, and all individuals had measured BMI, not just reported or recalled," said Professor Levi. "This is the largest study ever, including both men and women, and it had the power to prove the importance of BMI at age 17 on events later in life."

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