Study: Intermittent Fasting Helps Maintain Weight Loss for at Least One Year

A 12-week intermittent fasting program may help people maintain weight loss for at least a year after the structured intervention ends, according to a new study led by researchers at the University of Granada and published in Clinical Nutrition.

The study followed 99 adults with overweight or obesity, half of whom were women. Researchers found that participants who limited their daily food intake to an eight-hour eating window maintained significantly more of their weight loss than those who continued eating over 12 hours or longer each day.

The researchers evaluated the popular 16:8 intermittent fasting approach, in which people fast for 16 hours and eat during an eight-hour period. Participants followed either an early eating schedule (9:00 a.m.–5:00 p.m.), a late schedule (1:00 p.m.–9:00 p.m.), or selected their own eight-hour eating window.

One year after the 12-week program ended, both the early and late fasting groups had maintained greater weight loss than the control group. Participants following the early eating schedule also retained a greater reduction in body fat.

All participants received guidance on following a Mediterranean diet during the intervention. Researchers measured body weight, fat mass, and lean body mass before the program, immediately afterward, and again 12 months later.

The study is a follow-up to previous findings published in Nature Medicine, which showed that time-restricted eating resulted in an additional 3–4 kilograms of weight loss compared with nutritional counseling alone, regardless of when participants chose to eat.

Lead author Dr. Alba Camacho-Cardeñosa said that while previous research had shown modest short-term weight loss with intermittent fasting, it remained unclear whether the benefits would last.

"By evaluating participants 12 months after the intervention ended, we demonstrated that reductions in body weight were maintained over time," she said.

Researchers also found that one in three participants chose to continue practicing intermittent fasting on their own during the follow-up year, suggesting that the eating pattern is relatively easy to incorporate into everyday life.

The findings indicate that even a relatively short period of time-restricted eating may provide a practical medium-term strategy for weight management in adults with overweight or obesity. Because both early and late eating schedules produced lasting benefits, individuals may be able to choose the approach that best fits their lifestyle, potentially improving long-term adherence.