One of the biggest problems with weight-loss programs is not losing the weight — it is keeping it off. I have witnessed this with patients over the years and the research demonstrates it as well. Most people who lose weight through diet and lifestyle changes regain it within a year, and fewer than one in five maintain their loss long term. A new randomized controlled trial from the University of Granada in Spain puts time-restricted eating (TRE) to the test on exactly this question. Researchers followed 99 adults with overweight or obesity through a 12-week TRE intervention and then tracked them for a full year afterward, once they were no longer required to follow any prescribed eating schedule. Participants were assigned to one of four groups: usual care with Mediterranean diet education alone, an early eating window starting before 10:00 a.m., a late eating window starting after 1:00 p.m., or a self-selected window of their own choosing. Every TRE group followed an 8-hour eating window, while usual care kept its habitual pattern of 12 or more hours. This is the largest and longest study to date examining whether the timing of a restricted eating window affects long-term weight maintenance.
By the end of the 12-week intervention, TRE participants lost roughly 5% of their body weight. Twelve months later — after a full year of free-living conditions with no eating-window requirements — early and late TRE participants had maintained an average weight loss of about 2.5%, roughly half of what they achieved during the active intervention. That is a meaningful outcome: early TRE participants kept off 5.7 lb more than the usual-care group, and late TRE participants kept off 5.3 lb more. Waist and neck circumference improvements held up as well, particularly in the late TRE group, which sustained a 3.8 cm greater reduction in waist circumference and a 3.4 cm greater reduction in hip circumference compared with usual care. Notably, only 26% of participants reported continuing any form of TRE during the follow-up year, which means the benefits persisted even among people who had largely returned to unrestricted eating. The timing of the window — early or late — did not matter for long-term weight maintenance. What mattered was having done TRE at all during the initial 12 weeks.
Fat mass reduction remained significantly greater in the early TRE group at 12 months (3.5 lb more than usual care), while late TRE showed a similar trend without reaching the same statistical significance. The trade-off worth understanding is fat-free mass. Both early and late TRE groups lost more lean mass than usual care during the 12-week intervention, and this loss was only partially recovered a year later — a persistent reduction of about 2.2 to 2.4 lb compared with usual care. Participants who reported staying on TRE through the follow-up year had even lower fat-free mass than those who stopped. This pattern held across muscle mass in the thigh, measured directly by MRI, and a urinary marker of muscle protein breakdown. The takeaway is not that TRE is unsafe for muscle — it is that TRE without deliberate muscle-preserving strategies leaves lean mass on the table alongside fat.
For adults with overweight or obesity looking for a sustainable approach, an 8-hour eating window is a strategy worth committing to for at least 12 weeks, and the specific hours can be chosen based on personal schedule and lifestyle rather than a strict early-versus-late rule — both produced comparable long-term weight maintenance. Most of the weight loss happens in the first six weeks, so early results are a strong predictor of the pattern ahead, not a plateau to worry about. Because TRE reliably reduces fat-free mass alongside fat mass, pair the eating window with resistance training two to three times per week and prioritize adequate protein intake within the eating window to protect muscle. Sustaining even a portion of the initial results is worthwhile: participants who kept off half of their 12-week loss a year later did so with minimal ongoing restriction, which makes TRE a practical option for people who have struggled to maintain results from calorie-counting approaches. The strategy does not require permanent adherence to see lasting benefit, which is precisely what makes it usable in real life.
Camacho-Cardenosa, A., Merchán-Ramírez, E., Clavero-Jimeno, A., De-la-O, A., Romero-Noguera, J. M., Martín-Rodríguez, J. L., Muñoz-Torres, M., Labayen, I., Ruiz, J. R., & Dote-Montero, M. (2026). Effects of an early, late, and self-selected time-restricted eating intervention on weight loss maintenance in adults with overweight or obesity: A 12-month follow-up of a randomized controlled trial. Clinical Nutrition, 63, 106706. https://doi.org/10.1016/j.clnu.2026.106706
