Overweight, Obese BMI Associated With Increased Risk of Gastrointestinal Cancer

Overweight and obese gastrointestinal body mass index (BMI) in early and middle adulthood may be associated with an increased risk of gastrointestinal(GI) cancer, including colorectal cancer (CRC) and noncolorectal GI cancer, according to the results of a study published in JAMA Network Open. Overweight is a BMI between 25 and 29.9, obesity is a BMI of 30 or more.

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CRC is the third most common cancer among US patients. CRC incidence is high, despite better detection and screening, which could be caused by rising obesity rates. Obesity is associated with type 2 diabetes, metabolic disorders, and cardiovascular diseases (CVD). Excess weight gain may cause 20% of cancers; specifically, obesity is associated with chronic inflammation that is a risk factor for GI cancers, according to the study.

Previous data demonstrate that BMI influences risk of CRC cancer, but more research is needed. The current study is a secondary analysis of data from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, which was designed to reduce mortality from these conditions.

This retrospective study analyzed data of 135,161 participants, with an average age of 62 years, to explore the association between changing BMI and cancer risk. It aims to expand on previous research by analyzing the association between BMI at early, middle, and later adulthood (ages 20, 50, and 55 and older, respectively) with risk of noncolorectal GI cancer and CRC.

Primary outcomes included CRC and noncolorectal GI cancer diagnosis; association between BMI and cancer; association between cancer risk and BMI when age changes; and GI cancer risk from aspirin, which may prevent cancer according to epidemiological evidence.

Risk of CRC was associated with overweight BMI in early, middle, and late adulthood, and was associated with obese BMI in middle and later adulthood. The only statistically significant risk for noncolorectal GI cancer risk was static overweight or obesity between middle and later adulthood.

In addition, changing BMI increased risk of CRC and noncolorectal GI cancer, particularly increasing BMI from underweight or normal to overweight or obese BMI in later adulthood. Further, consistent overweight or obese BMI, and changing from overweight or obese to underweight or normal BMI, was also associated with increased risk of CRC.

Aspirin did not change the association between cancer risk and BMI. In fact, obesity may alter aspirin’s ability to prevent cancer, according to the study. Although some researchers may argue that it is necessary to increase aspirin frequency or dosage with weight, aspirin may cause GI bleeding, according to the current study.

Study limitations included that it is a secondary analysis of a completed trial, therefore, current exposure information is not included in the previous study. Aspirin dosing information was not included in the analysis, it was impossible to correlate changes in BMI with aspirin use, and investigators may not have accounted for all confounding variables.

Obesity is the buildup and storage of fat (adipose tissue). Adipose cells are inflammatory, may worsen immune function, and may lead to cancers that grow near adipose cells because it provides ample nutrients to the cancer cells. New cancer treatments could target the negative physiological effects of obesity.

“The results of the current study prompt further exploration into the mechanistic role of obese BMI in carcinogenesis,” the study authors wrote in the article.

Reference

Loomans-Kropp H, Umar A. Analysis of Body Mass Index in Early and Middle Adulthood and Estimated Risk of Gastrointestinal Cancer. JAMA Netw Open. 2023. doi:10.1001/jamanetworkopen.2023.10002