The Obesity Paradox in Colorectal Cancer May Reflect Prediagnostic Weight Loss

In the German multicenter study of 5,521 patients with colorectal cancer (CRC), the apparent survival advantage associated with overweight and obesity at diagnosis was largely explained by cancer-associated weight loss before diagnosis. Compared with patients with normal weight, those who were overweight had modestly better overall survival (HR, 0.89), whereas obesity was not associated with survival. In contrast, losing more than 10% of body weight during the 5 to 14 years before CRC diagnosis was strongly associated with worse survival (HR, 1.55). After simultaneously accounting for BMI at diagnosis and prediagnostic weight change, the apparent survival associations of overweight and obesity were attenuated to null. These findings suggest that the so-called “obesity paradox” in CRC may largely reflect prediagnostic cancer-associated weight loss rather than a true survival benefit of excess body weight. Therefore, the apparent survival advantage of overweight or obesity at diagnosis should not be interpreted as evidence that weight gain is beneficial for patients with healthy weight or as a reason to change existing survivorship recommendations. Source: https://jamanetwork.com/