O034 Preservation of fat free mass during rapid weight loss OSA

Introduction Obesity is a major risk factor for obstructive sleep apnoea (OSA). Very low energy diets (VLEDs) are effective for reducing weight but are associated with greater fat free mass (FFM) reduction where exercise may be protective. We aimed to assess the feasibility and tolerability of VLED-induced rapid weight loss with or without functional exercise in men with OSA and obesity. Methods This open-label pilot randomised controlled trial recruited men aged 18-55 years with BMI ≥27kg/m2 and untreated moderate-to-severe OSA to VLED-only (VO) or VLED-plus-exercise (VEX) for 12 weeks. Both groups followed a VLED providing <800kcal/day. The VEX group also participated in supervised functional exercise training. Results Nineteen men completed the study, with one drop out from VEX. Significant AHI reductions were observed in both VO (n = 9, -20.9events/hr [95%CI -28.3 to -13.6]) and VEX (n = 10, -12.4 events/hr [-21.7 to -3.1]). The VO group lost -16.6kg [-21.8 to -11.3] and -10.1kg fat mass [-8.2 to -1.9]. The VEX group lost -12.7kg [-17.1 to -8.3] and -8.6kg fat mass [-11.6 to -5.7]. FFM reduction occurred VO -5kg [-8.2 to -1.9] and VEX -3kg [-5 to -1.1]. Reduction in total AUC for glucose (-13.1 [-25.7 to -0.4; p=.04]) and insulin (-363.9 [-700.7 to -27.1 p=.04]) were significantly different between groups, favouring VEX. Discussion VLED, with or without exercise, proved feasible, tolerable and demonstrated positive improvement in AHI and body composition. Exercise induced favourable improvements in insulin sensitivity and the smaller reduction in FFM in the VEX group suggests exercise preserved FFM during VLED.