O009 Does exercise preserve fat free mass during rapid weight loss in overweight or obese men with obstructive sleep apnoea? A pilot study

Abstract 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 than other energy-restricted diets. Exercise may protect against this, having been shown to reduce OSA severity independently of weight loss. We aimed to assess the feasibility and tolerability of VLED-induced rapid weight loss with or without functional exercise in overweight or obese men with OSA. Methods This open-label pilot randomised controlled trial recruited men aged 18-55 years with a BMI of ≥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 at a commercial gym. Results Twenty men were recruited and completed the study, with one drop out from VEX. Significant AHI reductions were observed in both VO (n=9, -20.9 events/hr [95%CI -28.3 to -13.6]) and VEX (n=11, -15.4 events/hr [-26.0 to -4.7]). A total weight loss of -14.5kg [-17.5 to -11.5] and -9.3kg fat mass [-11.0 to -7.6] was achieved. FFM reduction occurred (-3.9kg [-5.5 to -2.3]), with a trend towards preservation in the VEX group. Discussion VLED, with or without exercise, proved feasible and well-tolerated and demonstrated positive outcomes in AHI and body composition variables. No between-group differences were observed in any outcomes, however the small reduction in FFM loss seen in the VEX group may suggest a potential mechanism for exercise to preserve FFM.