A study in the U.S. says that women who are overweight or obese have up to twice the risk of developing colorectal cancer before the age of 50 as women who have what is considered a normal body mass index (BMI). The study is among the first epidemiologic analyses of the potential contributors to early-onset colorectal cancer — cases diagnosed under age 50. The researchers found that higher current BMI, BMI at 18 years of age, and weight gain since early adulthood are associated with increased risk of colorectal cancer under age 50. The study included data from 85,256 women ages 25 to 44 in the United States’ Nurses’ Health Study II, which began in 1989. The researchers collected detailed information on body weight throughout the life course, family and endoscopy histories, and lifestyle factors at study baseline and every two to four years. Up to 2011, doctors diagnosed 114 colorectal cancer cases under age 50. The normal BMI range is 18.5-24.9 kilograms per square metre. BMIs from 25-29.9 are considered overweight, and BMIs greater than 30 are considered obese. The findings have been published in JAMA Oncology .
