Losing weight is the part that gets studied. Keeping it off is the part that decides whether any of it mattered, and it is studied far less often, because following people for a year after a trial ends is expensive and people drift away.
A Spanish team did it anyway. They took 99 adults with overweight or obesity through a 12-week trial of time-restricted eating, then came back twelve months after the intervention had finished to see what was left.
What they actually tested
Ninety-nine adults, half of them women, average age 49, average BMI 32. Everyone was randomly assigned to one of four groups, and — this matters for interpreting the result — everyone received the same Mediterranean diet education program, including the control group:
- Usual care (25 people): keep your habitual eating window of 12 hours or more.
- Early TRE (25 people): an 8-hour eating window starting before 10:00.
- Late TRE (27 people): an 8-hour eating window starting after 13:00.
- Self-selected TRE (22 people): an 8-hour window, you pick when.
Body weight and body composition were measured at the start, at 6 weeks, at the end of the 12-week intervention, and again 12 months later.
A year later, the difference was still there
Both early and late time-restricted eating had maintained significantly greater weight loss than usual care at the 12-month mark (p = 0.01 and p = 0.02). Pooling all three time-restricted groups strengthened the separation from usual care. Early TRE had also held onto more fat-mass loss specifically (p = 0.04).
Timing, in other words, mattered less than the fact of having a window at all. The morning eaters and the afternoon eaters both kept their advantage.
The finding that will not make the headlines
Fat-free mass stayed lower in the time-restricted groups too — significantly in late TRE (p = 0.04), and just short of it in early TRE (p = 0.051).
Fat-free mass is everything in the body that isn't fat: muscle, organs, bone, body water. It is the part you want to protect during weight loss, because it drives strength, mobility and how many calories you burn at rest. Losing some alongside fat is normal in any weight-loss intervention. What is notable here is that a year after the intervention ended, the deficit was still measurable. The people who restricted their eating window kept off more weight — and some of what they kept off was not fat.
That is not a reason to dismiss the approach. It is a reason to pair it with resistance training and adequate protein, which is standard advice during any weight loss and was not part of what this trial tested.
Only a quarter were still doing it
During the 12-month follow-up, just 26% of participants reported still practicing time-restricted eating.
Read that alongside the main result and it gets genuinely interesting. The weight advantage persisted in a group where three out of four people had stopped the actual behavior. Whatever carried the effect forward — changed eating habits, smaller portions, a different relationship with late-night snacking — it was not the eating window itself still being enforced.
What the study does not tell you
The published summary reports statistical significance at follow-up but not how many kilograms separated the groups. So "they kept off more weight" is supported; "they kept off X kg" is not, at least from what is publicly reported.
The self-selected window group is not listed among the schedules that held a significant advantage on its own — only early and late are. Body composition was measured with multi-frequency bioelectrical impedance, the method that sends a small current through the body to estimate fat and lean tissue. It is practical and repeatable but less precise than a DXA scan, and it is sensitive to hydration.
And the groups are small: 22 to 27 people each.
On funding and conflicts
Worth stating plainly, because this is a field crowded with people selling books and programs: all authors of this study declare no conflicts of interest. The work comes out of the Biosanitary Research Institute of Granada and the University of Granada, and the trial was preregistered (NCT05310721). No funding grants are indexed on the record, which is weaker evidence than the conflict statement — funding is not always indexed — but nothing on file points to commercial backing.
That does not make the findings correct. It does mean nobody involved declared a product riding on the outcome — which is not something that can be said of every prominent trial in this area.
The practical read
An 8-hour eating window, run for twelve weeks on top of ordinary Mediterranean-style eating advice, left a measurable trace a year later in people who had mostly stopped doing it. Morning or afternoon both worked. Protect your muscle while you do it, and treat the effect as real but modest — this is a small trial reporting a persistent difference, not a large one reporting a dramatic one.
Medical note. This article is for general education and is not personal medical advice. Time-restricted eating is not appropriate for everyone — including people who are pregnant, have a history of disordered eating, or take medication that must be tied to meals. Talk to your own clinician before making a substantial change to when or how much you eat.