Obesity, Overweight Individuals at a Heightened Risk of Colorectal Cancer

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There were significant positive associations found of overweight, obesity, and a 5-unit increase in BMI with colorectal cancer risk when using BMI measured 8-10 years prior to diagnosis.

Patients who are overweight or obese are at an increased risk of developing colorectal cancer, while those that exhibit weight loss actually decrease their risk of developing the cancer.1

A team, led by Marko Mandic, MSc, Division of Clinical Epidemiology and Aging Research, German Cancer Research Center (DKFZ), evaluated the association of body mass index and weight change with the risk of colorectal cancer when considering BMI at different time frames with the intention to account for prediagnostic weight loss.

A Growing Epidemic

The obesity rate is rising worldwide, also leading to an uptick in colorectal cancer risk. However, patients with colorectal cancer tend to lose weight prior to a diagnosis, which could lead to an underestimation of the association between being overweight or obese and the risk of colorectal cancer.

“According to the World Health Organization (WHO), overweight and obesity affected more than one-third of the global population in 2016, with around 2 billion adults and nearly 400 million adolescents and children being overweight or obese,” the authors wrote.

In the population-based case-control study, the investigators examined patients in southwestern Germany between 2003-2021 with a first diagnosis of colorectal cancer with comprehensive risk factor data and self-reported weight at different time points. The study also included a healthy control group matched by age, sex, and country.

The investigators sought main outcomes of the association of BMI and weight change at various points in time prior to and up to a diagnosis of colorectal cancer. This was assessed using multivariable logistic regression with comprehensive confounder adjustment. The study included 11,887 participants, 6434 with colorectal cancer and 5453 healthy control participants. The median age of the patient population was 69 years.

The Link to Colorectal Cancer

At the time of diagnosis, 62.1% (n = 3998) of cases and 66% (n = 3601) of the control group were considered overweight or obese. This suggestsan inverse relationship between excess weight and the risk of colorectal cancer.

On the other hand, there were significant positive associations found of overweight (adjusted odds ratio [aOR], 1.27; 95% confidence interval [CI], 1.03-1.56), obesity (aOR, 2.09; 95% CI, 1.61-2.70), and a 5-unit increase in BMI (aOR, 1.35; 95% CI, 1.21-1.50) with colorectal cancer risk when using BMI measured 8-10 years prior to diagnosis.

Higher BMI was seen as an especially pronounced risk factor for colorectal cancer earlier periods before diagnosis were examined, with the association being particularly pronounced using BMI at least 8 years before diagnosis.

However, there also was an association of weight loss (at or exceeding 2 kg) with colorectal cancer, with the greatest effect sizes occurring for weight loss within 2 years before diagnosis (aOR, 7.52; 95% CI, 5.61-10.09). This gradually decreased for earlier intervals.

“In this population-based case-control study, accounting for substantial prediagnostic weight loss further highlighted the association of overweight and obesity with CRC risk,” the authors wrote.


Mandic M, Safizadeh F, Niedermaier T, Hoffmeister M, Brenner H. Association of Overweight, Obesity, and Recent Weight Loss With Colorectal Cancer Risk. JAMA Netw Open. 2023;6(4):e239556. doi:10.1001/jamanetworkopen.2023.9556