Although previous studies already provide evidence for a link between obesity and some cancers, the team behind the new research point out that some may be flawed or biased due to weak study design and conduct.
The new review found 12 associations which were supported by strong evidence, strongly statistically significant results and no suggestion of bias.
The studies examined found strong associations between BMI and a risk of esophageal adenocarcinoma, colon and rectal cancer (in men), rectal (in men), biliary tract system, pancreatic, and kidney cancer, and endometrial (in premenopausal women).
The risk of postmenopausal breast cancer among women who never used hormone replacement therapy increased by 11% for each 5 kg of weight gain, and the risk of endometrial cancer increased by 21% for each 0.1 increase in waist to hip ratio.
The team also found additional associations supported by strong evidence between weight gain and the risk of colorectal cancer risk and between body mass index and risk of gallbladder, gastric cardia, and ovarian cancer, and mortality from multiple myeloma.
In addition, the results showed that the risk of developing cancer for every five-point increase in BMI ranged from a 9% increase for colorectal cancer among men, to 56% for biliary tract system cancer.
The team now call for even further research, as “evidence of the strength of the associations between obesity and cancer may allow finer selection of people at high risk, who could be selected for personalized primary and secondary prevention strategies.”
Cancer is a leading cause of death worldwide, and the prevalence of obesity has more than doubled over the past 40 years.