Adherence and Metabolic Outcomes of Early and Late Time-Restricted Eating with Energy Restriction vs. Energy Restriction Alone: A 6-Month Follow-Up

Background/Objectives: Long-term weight maintenance remains challenging with conventional dietary strategies due to various barriers. Time-restricted eating (TRE) has recently attracted attention as a potential approach to improve adherence, but evidence on long-term maintenance is limited. We investigated the 6-month follow-up (6FU) of early time-restricted eating with energy restriction (eTRE + ER), late time-restricted eating with energy restriction (lTRE + ER) and energy restriction alone (ER). Methods: This 6FU included 69 of 93 participants from a previously conducted 3-month intervention (3INT). After the intervention, participants returned to free-living conditions without dietary guidance. Outcomes included adherence, perceived barriers, body composition, blood pressure, cardiometabolic risk factors, metabolic hormones, subjective appetite, and dietary intake. Results: Adherence of at least ≥5 days per week was low: 7.7% (eTRE + ER), 18.2% (lTRE + ER), and 9.5% (ER). Reduced adherence during the 6FU was associated with a partial reversal of improvements in body mass, body composition, cardiometabolic risk factors, metabolic hormones, and subjective appetite observed during the 3INT. Analysis of perceived barriers showed that environmental and psychosocial barriers were significant predictors of changes in body mass during the 6FU, while environmental and behavioral barriers were associated with extension of the eating window. These associations were most pronounced in the eTRE + ER group. Conclusions: During the 6FU, differences between dietary strategies gradually diminished, although some remained clinically meaningful. Long-term adherence was low across all three dietary strategies, with psychosocial, environmental, and behavioral barriers particularly evident in the eTRE + ER group. Further research is needed to confirm long-term adherence before TRE + ER interventions can be widely applied in clinical practice.