It was recently postulated that a nutritional intervention aiming at achieving weight gain might increase survival in ALS patients. This article discusses the effect of nutritional status and weight gain on survival, respiratory status and physical function. Based on the available literature, it remains unknown whether weight gain during the progression of the disease improves survival whatever the baseline body weight is. A high body mass index may impair respiratory muscle function and passive mobilization of paretic patients. Future research should evaluate the effect of changes in weight and body composition on clinical outcome while taking into account respiratory muscle strength and physical function