Measuring obesity using body mass index (BMI) may not accurately reflect the link between obesity and colorectal cancer because people who later develop colorectal cancer often lose weight before diagnosis, making their BMI appear normal and weakening the observed association.

People who had a high body mass index (BMI) 8 to 12 years before being diagnosed with colorectal cancer were more than twice as likely to develop the disease compared to those with a normal BMI, suggesting that carrying excess weight over a long period increases risk, even if weight drops shortly before diagnosis.

People who have been overweight or obese for many years have a higher risk of developing colorectal cancer than those whose weight changed recently, with the highest risk linked to weight measured 8 to 12 years before diagnosis.

People who lose 2 kg or more unintentionally within two years before being diagnosed with colorectal cancer are 7.5 times more likely to have the disease, suggesting this weight loss may signal the presence of early-stage cancer.

Adults with obesity have a higher likelihood of developing colorectal cancer compared to those without obesity, based on data from millions of people across multiple studies.

People who gain fat specifically around the abdomen after being previously lean have a slightly higher chance of developing colorectal cancer at a younger age than those who never gained excess weight.