ORIGINAL ARTICLE Estimating dual-energy X-ray absorptiometry-derived total body skeletal muscle mass using single-slice abdominal magnetic resonance imaging in obese subjects with and without diabetes: a pilot study ST Baker 1,2 , BJ Strauss 3 , LA Prendergast 4 , S Panagiotopoulos 2 , GE Thomas 1 , T Vu 1 , J Proietto 1,2 and G Jerums 1,2 BACKGROUND/OBJECTIVES: Single-slice abdominal computed tomography or magnetic resonance imaging (MRI) performed to measure visceral adipose tissue in individuals with obesity and diabetes mellitus can also image skeletal muscle. The aim of this study was to validate a method developed in cancer patients using a single abdominal cross-sectional image to estimate fat-free mass (FFM) and appendicular lean tissue mass index (LTMI), a total body skeletal muscle mass surrogate, in an obese cohort of subjects with and without type 2 diabetes. SUBJECTS/METHODS: In total, 49 obese subjects (22 with diabetes) recruited into a weight loss study underwent dual-energy X-ray absorptiometry (DXA) and abdominal MRI at baseline. DXA-derived FFM and LTMI were compared with skeletal muscle area at the level of the third lumbar vertebra (L3) on MRI. RESULTS: L3 skeletal muscle area correlated with FFM (R adj 2 ¼ 0.825; Po0.001) and LTMI (R adj 2 ¼ 0.6; Po0.001). A simple formula, previously shown to predict LTMI in cancer patients, produced a good estimation of LTMI from L3 skeletal muscle area (95% confidence interval 3.70, 2.56%) in our obese cohort. Equations incorporating age, sex, height, weight and diabetic status improved the relationship between L3 skeletal muscle area and estimated FFM (r ¼ 0.976, Po0.001) and LTMI (r ¼ 0.879, Po0.001). CONCLUSION: A single-axial slice at the L3 level can be used to estimate FFM and LTMI in obese diabetic and non-diabetic subjects, allowing precise analysis of body composition using a single imaging modality in clinical research and practice. European Journal of Clinical Nutrition (2012) 66, 628--632; doi:10.1038/ejcn.2012.3; published online 25 January 2012 Keywords: body composition; fat-free mass; magnetic resonance imaging; obesity; skeletal muscle; type 2 diabetes INTRODUCTION Body composition analysis, that is, the measurement of the proportion of lean and adipose tissue, is an integral part of the assessment of individuals with obesity and obesity-related comor- bidities including type 2 diabetes mellitus. 1 In obesity, while both lean and adipose tissues are usually increased, it is the accumulation of intra-abdominal visceral adipose tissue (VAT) that is integral to the development of adverse metabolic outcomes including glucose dysregulation. 2-4 Interventions, including surgical and non-surgical interventions, aim to reduce the volume of VAT to ameliorate associated metabolic derangements and cardiovascular risk. 5 How- ever, the success of weight loss interventions in reducing fat mass including VAT is variable 6,7 and may be tempered by reductions in fat-free or lean body mass. 1 In obese individuals undergoing weight loss therapies, the decrease in skeletal muscle mass is of concern as this may contribute to impaired glucose homoeostasis, 8 reduced resting energy expenditure 9,10 and potentially, decreased weight maintenance in the intermediate to longer term. 11 Commonly used measurements of body composition utilise both dual-energy X-ray absorptiometry (DXA) for measurement of fat mass and fat-free mass (FFM) and abdominal imaging by computed tomography (CT) or magnetic resonance imaging (MRI) to assess VAT, which is sub-optimally quantified by DXA-based analysis. 12 - 14 However, the frequent acquisition of abdominal images and relative difficulty accessing DXA in certain clinical settings has led to studies investigating the use of axial imaging to predict total body lean tissue mass. A previous study showed that acquisition of a single abdominal image can allow estimates of total body skeletal muscle and adipose tissue in healthy adults. 15 More recently, a study by Mourtzakis et al. 16 in a cohort of cancer patients described the relationship between FFM and estimated total body skeletal muscle mass determined by DXA and muscle area in a single-slice CT image, thereby facilitating estimation of change in total skeletal muscle mass and also VAT by a single modality. Whether this relationship is also found in non-oncology patients is uncertain. The aim of this pilot study was to determine whether analysis of a single abdominal axial slice by MRI would allow estimation of total body skeletal muscle mass obtained by DXA in a cohort of obese subjects with and without type 2 diabetes mellitus. Received 14 November 2011; revised 4 January 2012; accepted 4 January 2012; published online 25 January 2012 1 Endocrine Centre, Austin Health, Heidelberg Repatriation Hospital Campus, Heidelberg West, Victoria, Australia; 2 Department of Medicine (Austin Health), University of Melbourne, Heidelberg West, Victoria, Australia; 3 Body Composition Laboratory, Monash Medical Centre, Department of Medicine, Monash University, Clayton, Victoria, Australia and 4 Department of Mathematics and Statistics, La Trobe University, Bundoora, Victoria, Australia. Correspondence: Dr ST Baker, Endocrine Centre, Austin Health, Heidelberg Repatriation Hospital Campus, PO Box 5444, Heidelberg West, Victoria 3081, Australia. E-mail: scott.baker@austin.org.au European Journal of Clinical Nutrition (2012) 66, 628 - 632 & 2012 Macmillan Publishers Limited All rights reserved 0954-3007/12 www.nature.com/