Intermittent Fasting Weight Loss: One-Year Results

Does intermittent fasting weight loss last a year later? Here's what the data shows

Yes, according to a 2026 one-year follow-up study — but with an important catch. People who followed a structured 8-hour eating window for just 12 weeks kept off more weight a year later than people who received only standard dietary advice, regardless of whether their eating window was early, late, or self-chosen. A separate, larger Cochrane review reached a more cautious conclusion, finding intermittent fasting didn't clearly outperform standard dieting overall. Both studies are real and recent — they're just asking slightly different questions.

The one-year follow-up: what researchers actually tracked

Researchers at the University of Granada followed up on a randomized trial testing time-restricted eating (TRE), a form of intermittent fasting where all food is eaten within a window of less than 10 hours a day. The results were published in Clinical Nutrition in 2026.

The study started with 99 adults, ages 30 to 60, who had overweight or obesity. For 12 weeks, participants were assigned to one of four groups: an early eating window starting before 10 a.m., a late window starting after 1 p.m., a self-selected window they picked themselves, or their usual, unrestricted eating pattern. Everyone, across all four groups, also received education on the Mediterranean diet and physical activity.

[REVIEWER: add clinical insight here — e.g., how you typically counsel patients choosing between early vs. late eating windows, and what you watch for regarding muscle loss in practice.]

What happened after 12 weeks ended

Researchers didn't tell anyone to keep or drop their eating pattern once the 12-week program finished. A year later, they checked back in. Of the original 99 participants, 65 completed the one-year assessment, and 26% said they'd kept doing time-restricted eating on their own.

The early and late time-restricted groups both maintained significantly greater weight loss than the group that ate on no fixed schedule. Pooled together, the three time-restricted groups also showed larger drops in fat mass, neck circumference, and waist circumference than the standard-advice group. Notably, most of the weight loss in the entire study happened within the first six weeks — the remaining months mostly maintained it rather than adding to it.

The catch: some of that "weight loss" wasn't fat

Not all the results were reassuring. In the late and self-selected eating-window groups, a meaningful share of the weight lost was fat-free mass — muscle and other lean tissue, not fat. The early eating window group held on to more of its fat-loss advantage with less lean-mass loss.

Randa Abdelmasih, an endocrinologist at UTMB who wasn't involved in the study, noted that this kind of lean-mass loss deserves real attention, since preserving muscle is now seen as central to healthy weight loss — especially as more people combine dietary changes with newer weight-loss medications. The study's own authors also cautioned that this was a secondary analysis with a fairly small final sample, and that self-reported adherence data has real limits.

The Cochrane review: a more skeptical verdict

Weigh the Granada findings against a separate 2026 Cochrane review, which pooled data from 22 randomized controlled trials and nearly 2,000 adults. That review concluded intermittent fasting did not produce a clinically meaningful weight-loss advantage over standard dietary advice or no structured intervention at all.

The two studies aren't necessarily contradicting each other so much as answering different questions. The Granada trial compared time-restricted eating plus Mediterranean diet coaching against Mediterranean diet coaching alone — both groups had structured guidance. The Cochrane review's comparison group often had no structured program at all. For anyone considering intermittent fasting as a completely standalone strategy, rather than layered on top of an existing healthy-eating plan, the Cochrane review's more cautious conclusion is worth taking seriously.

What about the heart-health concerns?

An earlier, widely reported study following over 20,000 adults found a link between 8-hour time-restricted eating and a higher rate of cardiovascular death. That finding generated significant media attention, but it came from observational data, not a controlled trial, meaning it can show an association without proving intermittent fasting caused the outcome. It hasn't been confirmed by the randomized evidence that exists so far, and the current one-year Granada trial reported no such safety signal. Anyone with existing heart disease or other cardiovascular risk factors should still discuss any fasting plan with a doctor before starting.

[REVIEWER: add clinical insight here — e.g., which patients you'd flag as needing extra caution or monitoring before starting time-restricted eating.]

Practical takeaway

If you're weighing intermittent fasting for weight loss, the most defensible reading of the current evidence is this: a simple, sustained eating window — paired with genuinely healthy food choices, not just calorie timing — can help some people keep weight off longer than diet advice alone, and it doesn't seem to matter much whether that window falls early or late in the day. But it isn't a guaranteed advantage over standard dieting, according to the larger Cochrane evidence, and it's worth pairing any fasting plan with adequate protein and resistance exercise to protect muscle mass. Talk to a doctor or registered dietitian before starting, particularly if you have any cardiovascular risk factors or a history of disordered eating.

FAQ

Does intermittent fasting weight loss actually last a year later? A 2026 follow-up study found that people who did 12 weeks of time-restricted eating maintained significantly more weight loss a year later than those who received standard dietary advice alone, regardless of whether their eating window was early or late in the day.

Does it matter what time of day the eating window is? Not much for total weight maintained, according to the Granada study — early, late, and self-selected windows all showed benefits. However, the early eating window preserved more fat mass and less muscle mass than the late or self-selected windows.

Does intermittent fasting cause muscle loss? It can. In this study, participants in the late and self-selected eating-window groups lost a notable amount of fat-free (lean) mass along with fat. Pairing fasting with adequate protein intake and resistance training is generally recommended to help protect muscle.

Is intermittent fasting better than standard dieting? The evidence is mixed. A 2026 Cochrane review of 22 trials and nearly 2,000 adults found no clinically meaningful weight-loss advantage over standard dietary advice. Other trials, like the Granada one-year follow-up, found a benefit when fasting was combined with dietary education.

Is time-restricted eating safe for heart health? An earlier observational study linked 8-hour eating windows to higher cardiovascular death rates, but it couldn't prove cause and effect, and randomized trials haven't confirmed the same risk. People with heart disease or related risk factors should talk to a doctor before starting any fasting plan.

5. Sources

• Camacho-Cardenosa, A. 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.

• Medical News Today: "Just 12 weeks of intermittent fasting may help sustain weight loss a year later: study," July 2026.

• Cochrane: "Intermittent fasting fails to beat standard dieting for weight loss," February 2026.

• ScienceDaily / University of Granada: "Intermittent fasting helped people keep weight off for a year," July 2026.