Amyotrophic lateral sclerosis (ALS) is the most common form of progressive motor neuron disease and the most devastating neurodegenerative disorder. ALS is characterized by progressive paralysis and respiratory failure leading to death within 3 to 5 years after its onset. Protein-energy malnutrition is a frequent finding in ALS. The pathogenesis of protein-energy malnutrition in ALS is multifactorial. Muscle atrophy, hypophagia, dysphagia, and hypermetabolism play a role in determining the deterioration of nutritional status. A multidisciplinary approach is crucial to set an appropriate plan for metabolic and nutritional support in ALS. Nutritional management incorporates a continuous assessment and implementation of dietary modifications throughout the duration of the disease. The nutritional and metabolic approaches to ALS should start when the diagnosis of ALS is made and should become an integral part of the continuous care to the patient, including nutritional surveillance, dietary counseling, management of dysphagia, and enteral nutrition when needed. Parenteral nutrition is rarely indicated. Standard polymeric enteral formulas are routinely used, usually providing 25 to 30 kcal/kg and protein 0.8 to 1.2 g /kg per day. The use of fiber-enriched formulas may help prevent constipation. However, considering the complex metabolic abnormalities of ALS, standard and/or fiber-enriched formulas might not be sufficient to achieve optimal metabolic and nutritional support. Based on the most recent clinical and experimental evidence, it is tempting to hypothesize that personalized nutritional support including specific nutritional substrates could act on disease progression and improve the quality of life and the response to the few and yet scarcely effective, currently available pharmacologic therapies.