Early Weight Loss in ALS Signals Faster Decline, but Standard Energy Formulas Fall Short

People with amyotrophic lateral sclerosis who lose weight early in their disease face a dramatically worse outlook, according to a prospective study published in the Journal of Neurology. Researchers led by Amber R. Sewell-Green and Frederik J. Steyn at the University of Queensland Centre for Motor Neuron Disease Research followed 170 people living with ALS and 173 non-neurodegenerative disease controls between March 2016 and October 2024. Their findings confirm that the scale can act as an early warning system, but they also deliver an uncomfortable message for clinicians: the predictive energy equations currently proposed for nutritional management in ALS perform poorly when tested against what actually happens to patients’ body weight.

ALS is the most common form of motor neuron disease, a progressive neurodegenerative disorder that typically claims lives through respiratory failure within two to five years of diagnosis. While the search for disease-modifying therapies continues, multidisciplinary care has become a cornerstone of improving quality of life. Within that care landscape, metabolism and nutrition have emerged as critical determinants of disease progression. Hypermetabolism, appetite loss, and malnutrition affect up to half of people living with ALS and are associated with faster functional decline and earlier death. Studies consistently show that loss of weight and fat mass predict poorer outcomes, whereas a higher body mass index is linked to slower progression.

The energy imbalance that drives this decline arises through multiple, often co-existing mechanisms. Skeletal muscle and mitochondrial dysfunction can elevate energy expenditure, while swallowing difficulties, upper-limb weakness, and reduced appetite simultaneously cut intake. Qualitative research has also documented substantial psychological and behavioural barriers that patients, carers, and healthcare professionals face when trying to adopt high-calorie diets. Despite growing recognition of these problems, clinicians have lacked clear guidance on how to identify emerging energy imbalance and translate it into individualized nutritional targets, and dietitians report considerable uncertainty about how best to calculate and adjust energy requirements for this population.

To address both questions at once, the Australian team designed a prospective case-control and within-case comparison study. Participants with ALS attended baseline anthropometric and metabolic assessments and were invited back for repeat visits every three to four months, accumulating 1794 participant-months of follow-up across 120 patients with two or more visits. Body composition was measured with whole-body air displacement plethysmography using a BOD POD system, and resting energy expenditure was assessed by indirect calorimetry under a canopy hood. Functional capacity was tracked with the revised ALS Functional Rating Scale, and the rate of functional decline was calculated as the monthly loss of points since symptom onset.

The researchers classified patients by their percentage weight change during the first six months after study inclusion, adapting the Global Leadership Initiative on Malnutrition criteria. Forty-nine participants were classed as Weight Gain, with a mean gain of 2.76 kilograms; 36 as Stable Weight, with a mean loss of 2.13 kilograms; and 35 as Weight Loss, averaging a striking 7.54-kilogram drop, or about 10 percent of body weight. Crucially, baseline body weight, body mass index, fat mass, fat-free mass, and measured resting energy expenditure were comparable across the three groups, meaning the classification itself, rather than pre-existing differences, marked the dividing line between diverging trajectories.

What followed the six-month landmark was stark. Using joint longitudinal-survival models that account for informative dropout associated with death, the team showed that patients in the Weight Loss group continued to lose body weight, body mass index, fat mass, and fat-free mass at the steepest rates, and their ALS Functional Rating Scale scores declined significantly faster than those of the other groups. Survival analysis told an even grimmer story: median survival from the landmark visit was 12.2 months for the Weight Loss group, compared with 26.8 months for Stable Weight and 31.8 months for Weight Gain. After sex adjustment, early weight loss carried an approximately five-fold higher mortality hazard relative to the Weight Gain reference group, with a hazard ratio of 4.78 and a confidence interval of 2.68 to 8.53.

The pattern of tissue loss carried its own diagnostic weight. Because body weight and fat mass declined in parallel, the authors argue that the weight loss reflects sustained negative energy balance rather than being attributable solely to loss of muscle mass. In the joint models adjusted for age and sex, higher longitudinal body weight showed the strongest anthropometric association with lower mortality risk, with a standardized hazard ratio of 0.42, while higher fat mass conferred a modest but significant protective association, with a standardized hazard ratio of 0.63. Patients with early weight loss also had lower respiratory and bulbar subscores at baseline and a faster rate of functional decline, consistent with computational modelling indicating that site of onset, respiratory function, and progression rate predispose patients to severe weight loss.

The second half of the study examined whether any of the predictive energy equations proposed for use in ALS could have anticipated these trajectories. In a nested cohort of 82 patients with three-day food diaries and repeat assessments, the researchers compared reported energy intake with equation-derived estimated energy requirements. Concordance was defined as alignment between the intake-to-requirement ratio and the observed weight-change category within a plus-or-minus 10 percent range, consistent with Australian dietary standards. The results were sobering: overall concordance ranged from just 17.3 percent for the Mifflin-St Jeor five-year equation to 32.1 percent for the best-performing model. No equation performed consistently across all weight-change groups.

Some equations failed in instructive ways. An ideal-body-weight-based approach using a body mass index target of 30, adapted from work by Nakamura and colleagues, showed the greatest concordance among patients who lost weight, correctly classifying 60 percent of them, but it generated excessively high energy targets for those who were weight-stable or gaining. Conversely, an equation assuming increased resting energy expenditure produced requirement estimates below reported intake across all groups, which would have suggested adequate or even excessive intake in patients who went on to lose weight. Sex-adjusted equations such as Harris-Benedict and Mifflin-St Jeor fared somewhat better in patients with mild weight loss of up to 5 percent. The authors conclude that no single equation should be applied universally, and that estimates derived at a single time point should never be interpreted in isolation.

The study’s implications point toward serial monitoring and phenotype-informed dietetic care rather than formula-driven prescription. Because weight loss may reflect, rather than cause, a more aggressive disease course, the observational design cannot establish causation, and randomized trials will be needed to determine whether stabilizing weight improves outcomes. Trials of high-calorie diets have shown promise in some patients, particularly those with faster-progressing disease, but results have been inconsistent, possibly reflecting differences in disease stage, metabolic phenotype, or the macronutrient composition of the interventions. Evidence of impaired metabolic flexibility, glucose intolerance, and altered lipid metabolism in ALS suggests that substrate utilization may matter as much as total calories, and observational studies linking higher fat intake with longer survival hint that dietary composition could be tailored to metabolic profile. The Sheffield-led OptiCALS randomized trial is currently testing whether an individualized high-calorie dietary intervention improves functional and nutritional outcomes. In the meantime, the message from Brisbane is clear: weigh patients early, weigh them often, and treat a five percent drop in six months as the clinical alarm it truly is.

Subject of Research: Prognostic value of early weight loss and the performance of predictive energy equations in amyotrophic lateral sclerosis

Article Title: Early weight loss predicts poorer prognosis and highlights limitations of predictive energy equations in amyotrophic lateral sclerosis

Article References: Sewell-Green, A. R., Capstick, R., Holdom, C. J., Matthews-Rensch, K., Cameron, J., McCombe, P. A., Henderson, R. D., Ngo, S. T., & Steyn, F. J. (2026). Early weight loss predicts poorer prognosis and highlights limitations of predictive energy equations in amyotrophic lateral sclerosis. Journal of Neurology, 273(10), Article 575. https://doi.org/10.1007/s00415-026-14093-5

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14093-5

Keywords: amyotrophic lateral sclerosis, weight loss, prognosis, energy balance, predictive energy equations, malnutrition, hypermetabolism, body composition, nutrition, motor neuron disease, survival, dietetic care