Obesity is a major global health challenge, and an established risk factor for several cancers. Adult weight gain has been associated with increased cancer risk, but studies on timing and duration of weight gain have been relatively scarce. Within the Metabolic Syndrome and Cancer Project (Me-Can 2.0), pooling data from six European cohorts, we examined the impact of BMI and weight changes over time, duration of excess weight, and age of first overweight measurement on obesity-related cancers. We also presented results for non-obesity-related cancers for comparison.
In this study, published in the International Journal of Epidemiology, we included approximately 220,000 individuals with two or more height and weight measurements, and constructed several BMI and weight measures. Almost 10,000 obesity-related cancer cases were diagnosed during follow-up. Using time-dependent Cox proportional hazards regression models, we evaluated the different measures in relation to cancer risk.
Adult weight gain was associated with increased risk of several major cancers, such as endometrial and postmenopausal breast cancer. The degree, timing and duration of overweight and obesity also seemed to be important. For example, being overweight before age 40 increased the risk of all obesity-related cancers by 15%, with higher risks particularly for endometrial, male renal cell, and male colon cancer. We found no positive associations for non-obesity-related cancers. Our key message is that preventing weight gain may be an important public health strategy to reduce the cancer risk.