A new study presented at the European Congress on Obesity (ECO) 2025 has found that time-restricted eating can support sustained weight loss, regardless of whether meals are consumed early or late in the day. The findings challenge long-standing views on optimal fasting windows amid rising global obesity rates.
Four Diet Groups, One Key Finding
The study, led by researchers at the University of Granada in Spain, involved 99 adults with overweight or obesity, averaging 49 years of age. Participants were randomly assigned to one of four groups for 12 weeks:
- Habitual eating (12+ hour eating window)
- Early TRE (8-hour window starting before 10:00 am)
- Late TRE (8-hour window starting after 1:00 pm)
- Self-selected TRE (participant-chosen 8-hour window)
Researchers tracked changes in weight, waist, and hip measurements at the beginning, after 12 weeks, and again 12 months post-study.
TRE Group Lost More Weight and Kept It Off
After three months, participants in all TRE groups experienced more weight loss than those in the habitual eating group. Waist and hip circumferences also shrank across all TRE participants, with the early TRE group seeing the most significant improvements.
“This finding shows that time-restricted eating can be an effective strategy for short-term weight loss, even without strict calorie counting,” said Dr Alba Camacho-Cardenosa, the study’s lead author and a postdoctoral researcher at the Instituto de Investigación Biosanitaria de Granada.
“It suggests that simply limiting the eating window may help people reduce their energy intake naturally and lose weight,” she added. More notably, the results held up a year later. While those in the habitual group regained weight and waist size, all three TRE groups maintained their weight loss.
“The fact that participants were able to maintain weight loss after 12 months shows that time-restricted eating can be a sustainable long-term approach,” said Camacho-Cardenosa.
“It means that this strategy does not just help people lose weight, but it can also help them maintain it, which is a major challenge in most weight loss programmes.”
Timing Less Important Than Fasting Duration
Dr Mir Ali, bariatric surgeon and director at MemorialCare Surgical Weight Loss Center in California, supported the study’s implications.
“What the study showed is that the time of day is not as important as the amount of time you stay away from eating,” Ali said. He emphasised the importance of strategies that help people maintain weight loss, given how often weight regain occurs after initial success.
He also called for more research on how TRE could integrate with specific diet types and determine the minimum effective fasting window.
How to Approach TRE Safely
Registered dietitian Monique Richard advised individuals to consider their personal schedule and health needs before starting a TRE regimen.
“Map out what a typical day looks like to take inventory… and ask if it would work to have those nutritional needs met within an eight-hour window,” Richard said. She encouraged people to be intentional about their eating patterns, asking: Why are you eating? How are you eating? What are you eating? When are you eating?
The latest study adds weight to the argument for time-restricted eating as a sustainable weight loss method. It demonstrates that while meal timing is less important, maintaining a consistent eating window can help individuals keep weight off in the long run.