Should patients with ALS gain weight during their follow-up?

• Body mass index (BMI) <18.5 kg/m2 appears to decrease survival, whereas BMI in the overweight and obese range seems to improve survival in patients with amyotrophic lateral sclerosis.
• Weight gain may improve survival but the effect of changes in body composition, physical activity, and modalities of nutritional and ventilatory support remains largely unknown.
• Recommendations regarding weight gain may depend on nutritional status, respiratory function, and patient's mobility.

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.