Predictions of resting energy expenditure in amyotrophic lateral sclerosis are greatly impacted by reductions in fat free mass

Abstract

Background: Hypermetabolism, defined as an increase in measured resting energy expenditure (mREE) relative to predicted REE (pREE), is recognised as an important feature of amyotrophic lateral sclerosis (ALS). Previous predictions of REE in ALS have not accounted for differences in fat free mass (FFM). This study aimed to investigate the effect of accounting for FFM on pREE in ALS patients and a matched control population. Methodology and findings: Body composition and pREE data were obtained from 50 ALS and 50 age-and sex-matched healthy control participants. We contrast conventional models for predicting REE that rely on anthropometric measures, age, and sex, with models that predict REE relative to FFM. Given that a significantly lower FFM was observed in ALS, models that consider FFM predicted significantly lower REE in ALS participants when compared to controls. Using Bland-Altman analysis, we demonstrate a prediction bias between models that do not account for FFM between the ALS and control populations. We also demonstrate greater agreement in predictions between control and ALS populations when correcting for FFM. Conclusions/significance: Future studies should correct for reductions in FFM when predicting REE in ALS. We conduct preclinical and clinical studies, researching factors that modify disease progression in ALS. As part of this process we are studying the impact of altered metabolism on disease progression. Here we address the important issue of altered energy needs in ALS. Existing studies that predict the resting energy needs of ALS patients do not correct for the loss of muscle mass that is seen in ALS. We show that changes in fat free mass (a key component of whole body energy use) in ALS compromises the accuracy of methods that are commonly used for predicting resting energy needs. Using a prediction model that corrects for fat free mass, we provide critical methodological insights to improve identification of altered energy needs in ALS. We are now conducting studies to identify the cause and effect of hypermetabolism in ALS.