The circadian timing of energy intake (EI) has emerged as a key factor in the regulation of body weight. Studies have suggested that eating meals later in the evening or during the biological night when the circadian system is promoting sleep adversely influences the success of weight loss therapy. In contrast, restricting EI to a short window during waking hours and extending the length of the overnight fast (i.e., time restricted feeding, TRF) may be a practical and useful strategy for promoting weight loss and weight maintenance. However, potential benefits of adding TRF to a weight loss program have yet to be evaluated in a well-controlled clinical study. The overall objective of this proposal is to provide a foundation to inform the design of a future large-scale trial to evaluate the efficacy of TRF in generating weight loss. The investigators overall hypothesis is that feasibility, adherence, and acceptability of a weight loss intervention using TRF in the setting of a reduced calorie diet (RCD) - RCD+TRF - will be similar to compliance with an intervention using a reduced calorie diet alone (RCD), suggesting acceptability for a future large-scale trial. In this 12-week pilot and feasibility study, 30 overweight and obese individuals will be randomized 1:1 to RCD+TRF (EI restricted to a 10-hour window starting 1 hour from habitual waking time) or standard RCD (no restriction on feeding duration). Additional follow-up will occur at 6 months to collect pilot data on weight maintenance. Measures include feasibility, acceptability and adherence to the interventions, body weight, body composition (Dual-energy X-ray absorptiometry (DXA)), EI (smart phone application), physical activity (PA, accelerometery), glucose variability (continuous glucose monitoring, CGM), sleep (questionnaires and polysomnography), and nocturnal substrate metabolism (room calorimetry). The specific aims (SA) are as follows:~Specific Aim 1a. To evaluate the feasibility and acceptability of a 12-week TRF intervention compared to a standard dietary weight loss intervention (i.e. RCD). Feasibility of enrollment and retention, and acceptability of the intervention will be assessed in adults with obesity meeting inclusion/exclusion criteria proposed for the future large-scale trial. The investigators will assess adherence to the weight loss programs, as measured objectively with a novel smartphone application and verified with CGM data, and subjectively with the use of questionnaires.~Specific Aim 1b. To assess the efficacy of RCD+TRF compared to RCD alone in producing weight loss at 12 weeks and reducing the risk of weight regain after 6 months of follow-up.
The circadian timing of Energy Intake (EI) has emerged as a key factor in the regulation of body weight. Studies have suggested that eating later in the evening or at night when the circadian system is promoting sleep adversely influences weight loss. In contrast, restricting EI to a short window during waking hours and extending the length of the overnight fast (i.e., time restricted feeding, TRF) may be a practical and useful weight loss strategy. The overall objective of this proposal is to provide a foundation to inform the design of a future large-scale trial to evaluate the efficacy of TRF in generating weight loss. The investigators aims are to: 1) Assess processes critical for the success of a large-scale trial comparing the efficacy of a reduced calorie diet with time restricted feeding (RCD+TRF) versus standard RCD on weight loss; 2) Develop methodology to assess compliance to the RCD+TRF versus standard RCD program and collect preliminary data on whether the programs have differential effects on free-living behaviors (EI, appetite, physical activity, and sedentary behavior); and 3) Measure metabolic responses to RCD+TRF versus standard RCD to determine candidate mechanisms related to weight loss at 12wks and weight maintenance at 6mo post-intervention. The investigators primary hypothesis is that weight loss will be greater in the TRF group compared to the RCD group.