Division of Research, Kaiser Permanente, Oakland, California.
Cancer Res. 2018 Apr 15;78(8):1906-1912. doi: 10.1158/0008-5472.CAN-17-3287.
Despite a greater risk of cancer associated with higher BMI, overweight (BMI 25-<30 kg/m) and class I obese (BMI 30-<35 kg/m) patients often have a paradoxically lower risk of overall mortality after a cancer diagnosis, a phenomenon called the "obesity paradox." Only when patients exceed a BMI ≥35 kg/m are elevations in mortality risk consistently noted. This paradox has been dismissed as the result of methodologic bias, which we will describe and debate here. However, even if such bias influences associations, there is growing evidence that body composition may in part explain the paradox. This phenomenon may more accurately be described as a BMI paradox. That is, BMI is a poor proxy for adiposity and does not distinguish muscle from adipose tissue, nor describe adipose tissue distribution. Low muscle mass is associated with higher risk of recurrence, overall and cancer-specific mortality, surgical complications, and treatment-related toxicities. Patients with who are overweight or obese have on average higher levels of muscle than their normal-weight counterparts. Also, there is some evidence that patients with moderate levels of subcutaneous adipose tissue may have lower mortality. More research utilizing body composition is needed to clarify the effects of adiposity on cancer mortality. .
尽管较高的 BMI 与更高的癌症风险相关，但超重（BMI 25-<30 kg/m）和 I 级肥胖（BMI 30-<35 kg/m）患者在癌症诊断后往往具有出乎意料的低总体死亡率风险，这种现象被称为“肥胖悖论”。只有当患者的 BMI≥35 kg/m 时，才会一致观察到死亡率风险升高。这种悖论被认为是方法学偏差的结果，我们将在这里对其进行描述和讨论。然而，即使这种偏差会影响相关性，越来越多的证据表明身体成分可能在一定程度上解释了这种悖论。这种现象可能更准确地被描述为 BMI 悖论。也就是说，BMI 是肥胖的一个很差的替代指标，它不能区分肌肉和脂肪组织，也不能描述脂肪组织的分布。低肌肉量与更高的复发风险、总体和癌症特异性死亡率、手术并发症以及与治疗相关的毒性有关。超重或肥胖的患者平均比体重正常的患者有更高水平的肌肉。此外，还有一些证据表明，中等水平的皮下脂肪组织的患者可能有更低的死亡率。需要更多利用身体成分的研究来阐明肥胖对癌症死亡率的影响。
