Most weight loss studies share a frustrating gap: they measure results right when a program ends, but rarely check back months or years later to see if those results actually last. A new study from the University of Granada set out to close that gap — and the findings offer some of the most encouraging long-term evidence yet for intermittent fasting.
Published in Clinical Nutrition, the official journal of the European Society for Clinical Nutrition and Metabolism, the study followed participants for a full year after a 12-week fasting intervention ended — and found that the benefits genuinely persisted.
The Study Design
Researchers followed 99 adults who were overweight or obese, with women making up half the participant group. The study examined the popular 16:8 intermittent fasting method — fasting for 16 hours each day and eating all meals within an 8-hour window.
During the first 12 weeks, all participants received education on following a Mediterranean diet. They were then divided into four groups:
Why The Human Body Has So Many Design Flaws — And Why That’s Actually A Fascinating Stor
- Control group — continued their usual eating pattern, spanning 12 hours or more daily
- Early fasting group — ate within an 8-hour window beginning before 10:00 a.m. (roughly 9am–5pm)
- Late fasting group — ate within an 8-hour window beginning after 1:00 p.m. (roughly 1pm–9pm)
- Self-selected group — chose their own 8-hour eating window based on personal preference
Researchers measured body weight, fat mass, and fat-free mass at the start and end of the 12-week program — and then again a full year after the intervention had concluded, to determine whether the changes had actually held up over time.
The Core Finding: Benefits Persisted A Year Later
The central question this study set out to answer was simple but important: does intermittent fasting produce lasting weight loss, or do the benefits fade once the structured program ends?
The answer was encouraging. One year after the intervention ended, both the early and late fasting groups had maintained significantly more weight loss than participants in the control group, who had continued eating across a longer daily window.
Notably, the benefit did not depend on which eating window participants used — both early (9am–5pm) and late (1pm–9pm) schedules produced lasting results. This is meaningful from a practical standpoint, since it suggests people can choose whichever eating window better fits their lifestyle, work schedule, or personal preference without sacrificing long-term effectiveness.
There was one notable distinction: participants in the early eating group preserved a larger reduction in fat mass specifically, compared to the other groups — suggesting that eating earlier in the day may offer some additional benefit for maintaining fat loss specifically, even if overall weight loss maintenance was similar across both timing groups.
What The Lead Researcher Said
Dr. Alba Camacho Cardeñosa, first author of the study and a researcher at the University Joint Institute for Sport and Health (iMUDS) at the University of Granada, explained why this long-term follow-up was so important.
“To date, although we knew that intermittent fasting promotes modest weight loss in the short term, it was unclear whether its effects were sustained over time,” she said. “By evaluating the participants 12 months after the intervention ended, we demonstrated that the changes in body weight persist.”
This distinction — between short-term weight loss and genuinely sustained weight loss — is critical in obesity research. Many interventions produce meaningful results while actively supervised, only for participants to regain much of the lost weight once the structured program ends. This study specifically addresses that concern by demonstrating durability well beyond the active intervention period.
The Encouraging Sign: People Kept Fasting On Their Own
Perhaps one of the most practically important findings from this research wasn’t about weight at all — it was about adherence.
The research team found that one in three participants chose to continue practicing intermittent fasting entirely on their own, without any structured program or supervision, throughout the full year of follow-up.
“A very positive finding is that one in three people decided to continue practicing intermittent fasting on their own during that year of follow-up, suggesting that it is a relatively easy habit to integrate into daily life,” the researchers noted.
This kind of spontaneous, self-directed continuation is a meaningful indicator of a diet approach’s real-world sustainability. Many weight-loss strategies produce good short-term results but prove genuinely difficult for people to maintain independently over the long term.
Part Of A Larger Research Project
This study builds on earlier findings from the same broader research project, whose primary results were published separately in Nature Medicine. That earlier work found that participants practicing time-restricted eating (TRE) lost an average of 3 to 4 kilograms more than people who received nutritional guidance alone — regardless of whether their eating window occurred earlier or later in the day.
Taken together, the two studies paint a consistent picture: time-restricted eating produces meaningful short-term weight loss, and — as this newer 12-month follow-up study demonstrates — those benefits appear to genuinely persist well beyond the structured intervention period.
A Flexible Approach To Weight Management
Professor Jonatan Ruiz Ruiz, who leads the PROFITH CTS-977 research group at the University of Granada through ibs.GRANADA, oversaw the broader study, which also involved collaborators from San Cecilio University Clinical Hospital, Virgen de las Nieves University Hospital, the Public University of Navarra, and multiple CIBER research networks focused on obesity and healthy aging.
According to the research team, even a relatively brief 12-week period of structured intermittent fasting could serve as an effective medium-term option for weight management in adults who are overweight or obese.
Because both early and late eating windows produced comparably durable results, the approach offers genuine flexibility — patients and clinicians can select whichever schedule best fits an individual’s work hours, family routine, or personal eating preferences, potentially improving long-term adherence and making the strategy more practical as part of broader obesity treatment approaches.
What This Means For You
If you’re considering intermittent fasting as a weight management strategy, this research offers several practical takeaways:
- The 16:8 method (8-hour eating window, 16-hour fast) has demonstrated evidence for both short-term weight loss and longer-term maintenance
- Timing flexibility — you don’t need to force an early eating window if it doesn’t fit your schedule; a later window showed comparable weight maintenance benefits
- Earlier eating may offer a slight edge for preserving fat mass specifically, if that’s a priority and compatible with your routine
- Combining fasting with dietary quality — this study paired fasting with Mediterranean diet education, suggesting the eating pattern works best alongside genuinely nutritious food choices, not as a license to eat poorly within the eating window
- Sustainability matters — the fact that a third of participants continued independently suggests this approach may be more realistic to maintain long-term than more restrictive diet strategies
Key Takeaways
- A 12-week intermittent fasting (16:8) program produced weight loss benefits that persisted a full year after the intervention ended
- Both early (9am-5pm) and late (1pm-9pm) eating windows produced lasting weight loss maintenance
- The early eating window group preserved a larger reduction in fat mass specifically
- One in three participants continued practicing intermittent fasting independently throughout the year-long follow-up
- This research builds on earlier findings showing time-restricted eating produced 3-4 kg more weight loss than nutritional guidance alone
When To See A Healthcare Professional
If you’re considering intermittent fasting, especially if you have diabetes, are pregnant or breastfeeding, have a history of disordered eating, or take medications that require food, consult your doctor or a registered dietitian before starting. They can help determine whether this approach is appropriate and safe for your individual health circumstances.
⚠️ Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any new dietary or fasting regimen.
Source: University of Granada — July 18, 2026
Journal Reference: Alba Camacho-Cardenosa, Elisa Merchán-Ramírez, Antonio Clavero-Jimeno, et al. 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, 2026; 63: 106706.
DOI: 10.1016/j.clnu.2026.106706
