Anthropometric measures are not accurate predictors of fat mass in ALS

Abstract

Background: Anthropometric measurements including body mass index (BMI) and body adiposity index (BAI) are widely employed as indicators of fat mass (FM). Metabolic abnormalities in amyotrophic lateral sclerosis (ALS) impact disease progression, therefore assessment of FM informs care. The aim of this study was to determine whether BMI and BAI are accurate predictors of FM in ALS.

Methodology and main findings: BMI, BAI and percentage FM (determined by air displacement plethysmography; FM-ADP) were measured in control (n = 35) and ALS (n = 44) participants. While BMI and BAI correlated significantly with FM-ADP, neither index provided an accurate estimate of FM. In longitudinally assessed ALS participants (n = 29; ∼six-month repeat assessment interval), although a change in BMI (r² = 0.62 r = 0.79 p < 0.01) and BAI (r² = 0.20

r = 0.44, p = 0.02) correlated with a change in FM-ADP, the anthropometric measures did not consistently reflect increases or decreases observed in FM-ADP.

Conclusions/significance: Using FM-ADP as the standard, this study suggests that BMI and BAI are not accurate measures of FM in ALS. Furthermore, longitudinal assessments indicate that changes in BMI and BAI do not consistently reflect true changes of FM in ALS.

Keywords:

• Amyotrophic Lateral Sclerosis
• adiposity
• fat mass
• body adiposity index
• body mass index
• air displacement plethysmography
• metabolic assessment

Acknowledgements

This work was part-funded by Grants-in-Aid from the Motor Neurone Disease Research Institute of Australia (MNDRIA; the Cunningham Collaboration MND research Grant and the Cunningham Family Research Grant) to STN, FJS, PAM and RDH, Royal Brisbane & Women's Hospital Foundation grants to RDH and the University of Queensland. STN acknowledges the support of a Scott Sullivan MND Research Fellowship (2015–2018) funded by The MND and Me Foundation, The Royal Brisbane &Women's Hospital Foundation, and the Queensland Brain Institute. ZAI is supported by The Australian and New Zealand Association of Neurologists (ANZAN) Education and Research Foundation/National Health and Medical Research Council (NHMRC) Post-Graduate Scholarship. We extend our gratitude to Kathryn Thorpe, Susan Heggie and Nicole Hutchinson (RBWH), and Vicki Allen and Lisa Dingwall (CCR) for their support and assistance. We extend our sincerest gratitude to all ALS patients and control volunteers who participated in this study.

Declaration of interest

No potential conflict of interest was reported by the authors.

Supplementary material available online