Amyotrophic lateral sclerosis (ALS) alters nutritional state, energy intake and energy expenditure. This article aims at reviewing present knowledge on these topics in order to determine energy requirements for maintaining a neutral energy balance in ALS patients. Maintaining a neutral energy balance prevents malnutrition and its complications and may improve physical functioning, quality of life and survival. Prevalence of malnutrition varies between 16 and 55% in ALS patients. Energy intakes are below recommended dietary allowances in 70% of ALS patients at least. These elements suggest a chronic negative energy balance with an imbalance between requirements and intakes. While insufficient intakes can be compensated with nutritional support, the energy requirements are unclear. Studies generally report hypermetabolism in ALS patients. Estimation of total energy expenditure and as a corollary energy needs, necessitates taking into account this hypermetabolism, physical activity and possibly mechanical ventilation. The review suggests a flow chart for optimal nutritional follow-up in clinics. Further studies are required to assess whether optimal nutritional follow-up improves outcome.