A short-term commitment to intermittent fasting may deliver long-term weight management benefits, according to new research from the University of Granada. Scientists tracked nearly 100 overweight and obese adults through a 12-week fasting program and found that those who restricted eating to an eight-hour window maintained their weight loss a year after the intervention ended, while control participants who ate across 12 hours or more gradually regained what they'd lost.
The study, published in Clinical Nutrition, focused on the 16:8 approach to intermittent fasting, where participants fast for 16 hours daily and consume all meals within an eight-hour window. All 99 participants initially received education about Mediterranean diet principles during the first 12 weeks, then were split into four groups: a control group that maintained its normal eating schedule, an early fasting group eating between 9 a.m. and 5 p.m., a late fasting group eating between 1 p.m. and 9 p.m., and a self-selected group that chose their own timing.
The timing of the eating window did not matter. Both early and late fasting groups preserved significantly more weight loss after 12 months than the control group, though the early eaters showed a slightly better reduction in fat mass specifically. Researchers measured body weight, fat mass, and fat-free mass at baseline, after the 12-week program, and again one year later.
The most striking finding came not from the lab but from behavioral persistence: one in three participants continued practicing intermittent fasting on their own throughout the year-long follow-up period, suggesting the approach is manageable outside a clinical setting. Alba Camacho Cardeñosa, the study's lead author and a researcher at the University of Granada, noted that while researchers knew intermittent fasting produced weight loss in the short term, it was unclear whether those gains would stick. "By evaluating the participants 12 months after the intervention ended, we demonstrated that the changes in body weight persist," she said.
The research aligns with earlier findings from a larger project published in Nature Medicine, which showed that participants practicing time-restricted eating lost three to four kilograms more than people who received only nutritional guidance, regardless of when they ate. The new follow-up data suggests this modest initial advantage compounds into meaningful long-term weight management.
From a practical standpoint, the flexibility of the approach could improve adoption rates. Patients can choose an eating window that fits their daily schedule, whether they're morning risers or night owls, without sacrificing results. For obesity treatment, researchers see potential in offering a structured 12-week intervention as a medium-term weight management option that patients can extend on their own if they find it sustainable.
The study involved collaborators from multiple Spanish institutions, including the Granada Institute for Biomedical Research, the Public University of Navarra, and several university hospitals. The research group is part of a broader effort to identify practical, evidence-based treatments for obesity and related metabolic disorders.
Author Jessica Williams: "This study doesn't promise a weight loss miracle, but it does suggest that eight hours of eating and 16 hours of fasting can stick as a habit if it works for you in the first place."
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