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

Augmented renal clearance, often abbreviated ARC, describes a condition in which the kidneys filter blood at a rate well above what would be expected for a given patient. It has been recognized for more than a decade in critically ill trauma and sepsis patients, where it is usually treated as a pharmacokinetic problem: drugs that are cleared by the kidneys, particularly antibiotics, are eliminated so quickly that standard doses may fail to reach therapeutic levels in the blood. The Montreal team, led by neurosurgeon Kazunori Oda, set out to ask a different question. Rather than viewing the hyperfiltering kidney purely as a dosing challenge, they hypothesized that it might serve as a window into a broader hyperdynamic state, one that also drives the catabolic firestorm that follows severe brain injury.

The study examined intensive care unit admissions of adults with severe traumatic brain injury at a tertiary academic level I trauma center between 2015 and 2024. Because directly measured urinary creatinine clearance was not systematically available in this retrospective setting, the researchers relied on serum-creatinine-estimated creatinine clearance, calculated from routine blood work. They defined estimated augmented renal clearance, or eARC, as an estimated creatinine clearance of at least 130 milliliters per minute per 1.73 square meters of body surface area at one or more time points during the first 28 days after injury. This threshold is consistent with definitions used widely in the critical care literature, where values above 130 are generally considered supranormal.

Of the 342 admissions included in the analysis, eARC occurred in 197 patients, or 57.6 percent. That figure is striking: it means that in this population, a hyperfiltering kidney was the rule rather than the exception. The patients who developed eARC were younger, more often male, and had lower admission Glasgow Coma Scale scores, suggesting more severe impairment of consciousness at presentation. These demographic and clinical associations echo earlier work showing that young trauma patients with robust physiological reserve are the ones most likely to mount an exaggerated renal response, even as their brains bear the brunt of the injury.

The central finding of the study concerns body weight. Patients with eARC experienced a median day-28 body weight loss of 12.7 percent, compared with essentially no change, 0.0 percent, in patients without eARC, a difference that was highly statistically significant. Severe weight loss was also markedly more frequent in the eARC group. To put the magnitude in perspective, a double-digit percentage loss of body mass within a month is far beyond what would be expected from simple fluid shifts or reduced appetite; it points to substantial depletion of lean tissue and fat stores, the kind of catabolic erosion that has been associated with worse outcomes in critically ill and neurotrauma populations.

To make sure the association was not an artifact of confounding, the investigators took a rigorous approach to variable selection, guided by a directed acyclic graph, a formal framework that maps out plausible causal relationships and identifies which covariates must be adjusted for. In exploratory multivariable analysis adjusting for age and admission Glasgow Coma Scale score, eARC remained independently associated with severe day-28 weight loss. The team also ran a battery of sensitivity analyses designed to rule out alternative explanations. They incorporated calories derived from propofol, the sedative commonly infused in brain-injured patients, which is delivered in a lipid emulsion and can contribute substantial energy intake that is often overlooked in nutrition calculations.

Those sensitivity analyses proved revealing in their own right. Once propofol-derived calories were counted, total energy delivery turned out to be similar between the eARC and non-eARC groups, which weakens the argument that the weight loss simply reflected underfeeding. Likewise, serum sodium concentrations, total fluid input, urine output, and the input-minus-urine fluid balance estimate did not show clear group-level differences that could account for the observed weight-loss gap. In other words, the excess weight loss in eARC patients could not be readily explained by either a caloric deficit or by large-scale fluid and electrolyte shifts, leaving a primary metabolic or catabolic mechanism as the leading candidate.

The biological plausibility of such a mechanism is supported by a growing body of literature. Severe traumatic brain injury is known to trigger one of the most intense hypermetabolic states in medicine, with resting energy expenditure and nitrogen excretion rising sharply in the first weeks after injury. Previous observational work has linked augmented renal clearance to increased muscle catabolism and urinary nitrogen loss in trauma patients, and studies of atrial natriuretic peptide and cardiac output in brain-injured patients have suggested that the hyperdynamic circulation driving renal hyperfiltration may be part of a systemic stress response. Creatinine itself is generated from muscle, so a rapidly falling serum creatinine in a catabolic patient can inflate clearance estimates while simultaneously signaling loss of muscle mass, a coupling that the authors acknowledge as a limitation of relying on estimated rather than measured clearance.

The clinical implications, if confirmed, could be substantial. If eARC identifies a metabolically vulnerable subgroup of brain-injured patients, then a routine serum creatinine, a test drawn almost daily in every intensive care unit, could become an early warning flag prompting intensified nutritional surveillance, earlier dietitian involvement, closer monitoring of protein delivery, and perhaps pharmacokinetic dose adjustments for renally cleared drugs. The authors are careful to frame their findings as hypothesis generating. Because the study was retrospective and relied on estimated rather than measured creatinine clearance, and because body weight alone cannot distinguish fluid changes from true tissue loss, they call for prospective studies using directly measured creatinine clearance, detailed sodium and water balance assessment, and direct body composition measures such as bioelectrical impedance or imaging-based muscle quantification.

For now, the study adds an intriguing piece to the puzzle of why some brain injury patients waste away despite modern critical care. It suggests that the kidney, an organ rarely at the center of neurotrauma discussions, may be broadcasting a signal about systemic metabolic state that clinicians have been reading only through a pharmacokinetic lens. With more than half of severe traumatic brain injury patients in the cohort showing supranormal renal filtration, and with that subgroup losing on average nearly 13 percent of their body weight in a month, the case for watching the kidneys as metabolic sentinels has become considerably stronger. Whether aggressive, eARC-guided nutritional intervention can change the trajectory for these patients is the question that prospective research must now answer.

Subject of Research: Augmented renal clearance and metabolic weight loss after severe traumatic brain injury

Article Title: Serum-Creatinine-Estimated Augmented Renal Clearance is Associated with Marked Weight Loss after Severe Traumatic Brain Injury

Article References: Oda, K., Nedelcu, R., Abouassaly, M., Mourad, A. A., Grubb, K., Saluja, R. S., & Marcoux, J. (2026). Serum-Creatinine-Estimated Augmented Renal Clearance is Associated with Marked Weight Loss after Severe Traumatic Brain Injury. Neurocritical Care. https://doi.org/10.1007/s12028-026-02666-1

Image Credits: AI Generated

DOI: 10.1007/s12028-026-02666-1

Keywords: augmented renal clearance, traumatic brain injury, neurocritical care, creatinine clearance, weight loss, nutrition, catabolism, fluid balance, intensive care, hypermetabolism, neurotrauma, propofol