This study aims to investigate whether CBTI can enhance the effectiveness of TRE for weight control in adults with chronic insomnia and overweight or obesity. This assessor-blinded, two-arm, parallel-group randomized controlled pilot trial plans to recruit 50 Chinese adults aged 18 years or older with chronic insomnia and overweight or obesity (BMI ≥23 kg/m²) in Hong Kong. Participants will be randomized (1:1) to a flexible time-restricted eating group (FTRE, n=25) or a flexible time-restricted eating plus CBTI group (CBTI+FTRE, n=25). Both groups will follow a 16:8 time-restricted eating schedule for 12 weeks, while participants in the CBTI+FTRE group will additionally receive a 12-week group-based CBTI program consisting of biweekly 90-minute sessions. Assessments will be conducted at baseline, post-intervention (week 12), and follow-up (week 24). The primary outcome is body weight. Secondary outcomes include body mass index, waist and neck circumferences, body composition, insomnia severity, sleep quality, objective and subjective sleep parameters, physical activity, blood pressure, appetite, food intake, eating window, and exercise habits. We hypothesize that the addition of CBTI to TRE will result in greater weight loss and improved sleep outcomes compared with TRE alone
