How does weight loss occur in ALS?

Unwanted weight loss affects more than 50% of people with ALS. The most common cause of weight loss in ALS is dysphagia and reduced food intake. Another reason may be an increased energy requirement caused by respiratory dysfunction. The respiratory weakness may require increased work of breathing and an increased energy requirement. If the energy requirement is not met, this results in a negative energy balance and weight loss. Irrespective of the factors of dysphagia (reduced food intake) or respiratory dysfunction (increased nutritional requirements), an ALS-related metabolic disorder may be present, which is described as “hypermetabolism”. This refers to an increase in the resting energy metabolism: Even without physical exertion, more energy is required to maintain the body’s functions. The three factors of weight loss (dysphagia, respiratory work and energy metabolism) can be present individually or in combination. For targeted treatment, it is necessary to differentiate between these factors and for doctors and nutritional therapists to have the relevant expertise.