Purpose: To systematically evaluate the impact of diet, exercise and lifestyle modification programmes on indices of obesity, Obstructive Sleep Apnoea (OSA) parameters and quality of life (QoL) in adults with OSA. Methods: Electronic databases were searched to identify randomised controlled trials published in English with an intervention based on dietary weight loss, exercise and/or lifestyle programme in adults with OSA. Meta-analyses were conducted using random-effects models. Results: Twelve studies met the inclusion criteria with nine comparing similar interventions. Diet and diet plus continuous positive airway pressure (CPAP) therapy were compared in three studies (n = 261), and intensive lifestyle programmes and routine care were compared in six studies (n = 483). Diet with CPAP therapy reduced weight by -2.64 kg (95 % Confidence Interval (CI) -3.98, -1.30, I (2) = 0 %) compared with diet alone. No differences were observed for QoL or Epworth Sleepiness Scale. A significant reduction in weight was seen in participants receiving an intensive lifestyle intervention of -5.65 kg (95 % CI -10.91, -0.40, I(2) = 95.7 %) compared with controls. Reductions were also observed for waist circumference (-5.80 cm, 95 % CI -8.64, -2.96, I(2) = 77.7 %), body mass index (BMI) (-2.33 kg/m(2), 95 % CI -3.41, -1.24, I(2) = 78.8 %) and the Apnoea Hypopnoea Index (AHI) (-4.55 events/h, 95 % CI -7.12, -1.98, I(2) = 54.4 %) but with high levels of heterogeneity. Conclusions: Intensive lifestyle management can significantly reduce obesity indices and improve AHI. Future research is required to investigate this effect due to a limited number of studies identified.