Other ; This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Oxford University Press. ; Abstract ; Abnormal eating behaviour and metabolic parameters including insulin resistance, dyslipidaemia and body mass index are increasingly recognized as important components of neurodegenerative disease and may contribute to survival. It has previously been established that behavioural variant frontotemporal dementia is associated with abnormal eating behaviour characterised by increased sweet preference. In this study, it was hypothesized that behavioural variant frontotemporal dementia might also be associated with altered energy expenditure. A cohort of 19 patients with behavioural variant frontotemporal dementia, 13 with Alzheimer’s disease and 16 (age- and sex- matched) healthy controls were studied using Actiheart devices (CamNtech, UK) to assess resting and stressed heart rate. Actiheart devices were fitted for 7 days to measure sleeping heart rate, activity levels, and resting, active and total energy expenditure. Using high resolution structural MRI the neural correlates of increased resting heart rate were investigated including cortical thickness and region of interest analyses. In behavioural variant frontotemporal dementia, resting ($p$=.001), stressed ($p$= .037) and sleeping heart rate ($p$=.038) were increased compared to controls, and resting heart rate ($p$=.020) compared to Alzheimer Disease patients. Behavioural variant frontotemporal dementia was associated with decreased activity levels compared to controls ($p$= .002) and increased resting energy expenditure ($p$= .045) and total energy expenditure ($p$=.035). Increased resting heart rate correlated with behavioural (Cambridge Behavioural Inventory) and cognitive measures (Addenbrooke’s Cognitive Examination). Increased resting heart rate in behavioural variant frontotemporal dementia correlated with atrophy involving the mesial temporal cortex, insula, and amygdala, regions previously suggested to be involved exclusively in social and emotion processing in frontotemporal dementia. These neural correlates overlap the network involved in eating behaviour in frontotemporal dementia suggesting, a complex interaction between eating behaviour, autonomic function and energy homeostasis. As such the present study suggests that increased heart rate and autonomic changes are prevalent in behavioural variant frontotemporal dementia, and are associated with changes in energy expenditure. An understanding of these changes and neural correlates may have potential relevance to disease progression and prognosis. ; Other ; National Health and Medical Research Council of Australia (Grant IDs: 1037746, 1003139, 1022684), Australian Research Council Centre of Excellence in Cognition and its Disorders Memory Node (Grant ID: CE110001021), Royal Australasian College of Physicians (PhD scholar), MND Australia (PhD scholar), Wellcome Trust, Medical Research Council, European Research Council, National Institute for Health Research Cambridge Biomedical Research Centre, The Bernard Wolfe Endowment, Swiss National Science Foundation (Grant IDs: PBLAP3-145870, P3SMP3-155318)