People who repeatedly lose weight only to gain it back again may find it easier to stick with intermittent fasting than with traditional calorie counting—according to a new study from the University of Adelaide. The study examined not only how much weight the participants lost, but also how different dietary approaches affected their eating habits, mood, sleep, and overall quality of life. The researchers found that intermittent fasting and continuous calorie restriction led to similar weight loss. However, participants who followed the fasting plan did not feel they had to constantly monitor their diet, avoid overeating, or count calories to achieve these results.

A Different Mental Approach to Weight Loss

This experience differed from that of the individuals who followed a calorie-restricted diet. These participants reported that losing weight required a constant effort to consciously limit food intake and resist overeating. The researchers estimated that this increased sense of control accounted for about 15% of their weight loss.

“While many diets can lead to weight loss, they are often difficult to stick to, making it hard to maintain weight loss in the long term,” said Professor Leonie Heilbronn of the University of Adelaide’s School of Medicine and the South Australian Health and Medical Research Institute. “The results of our study suggest that intermittent fasting could be an alternative for people who find conventional diets difficult.”

Similar Weight Loss, Different Experiences

More than 200 adults with obesity participated in the 18-month clinical trial. Participants were randomly assigned to one of three groups: intermittent fasting, continuous calorie restriction, or standard care. Participants in the intermittent fasting group consumed 30% of their daily energy needs between 8 a.m. and 12:30 p.m. on three non-consecutive days per week. After this eating window, they fasted for 20 hours. On all other days, they ate as usual.

Participants in the continuous calorie restriction group consumed about 70% of their normal daily calorie intake each day. The standard care group maintained their usual diet but received guidelines for healthy eating. After six months, participants in both the intermittent fasting group and the calorie restriction group had lost an average of about seven kilograms. In comparison, those who received standard care lost only about two kilograms.

Participants in both diet groups also reported improvements in depression and overall well-being, even on fasting days. The results, published in the journal Clinical Nutrition, suggest that intermittent fasting and calorie restriction can promote weight loss through different psychological and behavioral mechanisms. “Psychological and behavioral factors have a major influence on how well people can stick to diets. Intermittent fasting could help people lose weight without having to consciously restrict their food intake,” said Professor Heilbronn.

Intermittent Fasting Can Help People Maintain their Weight for a Year

Other recent research also shows that specific fasting programs can effectively support people in managing their weight. A 12-week intermittent fasting program can help people maintain their weight loss for at least a year after completing the structured intervention. This is the conclusion of a study in which the University of Granada (UGR) participated.

The study, published in Clinical Nutrition, followed 99 overweight or obese adults. Half of the participants were women. The researchers found that limiting daily food intake to an eight-hour window helped participants retain a larger portion of their weight loss than was the case with a 12-hour or longer eating window.

The researchers examined the popular 16:8 method of intermittent fasting. With this method, participants fast for 16 hours each day and eat their meals during the remaining eight hours. The sustained benefits did not depend on whether participants ate earlier or later in the day. Under the early schedule, eating was permitted between 9 a.m. and 5 p.m., while the later schedule utilized a window between 1 p.m. and 9 p.m.

One year after the end of the intervention, both the group with the early fasting schedule and the group with the late fasting schedule had maintained significantly more weight loss than participants who continued to eat for 12 hours or longer each day. Those assigned to the early schedule also showed a greater reduction in fat mass. The results suggest that time-restricted eating may be feasible in the short term while producing effects that last well beyond the original program.

Measurement of Weight and Body Composition

The study was published in Clinical Nutrition, the official journal of the European Society for Clinical Nutrition and Metabolism. Researchers from the University of Granada (UGR), the Institute for Biomedical Research in Granada (ibs.GRANADA), the Public University of Navarra, and the Network for Biomedical Research (CIBER) participated in the study. During the first 12 weeks, all 99 participants received training on adhering to a Mediterranean diet. They were then divided into four groups.

The control group maintained their usual daily eating window of 12 hours or more. The early-fasting group adhered to an 8-hour window that began before 10:00 a.m. The late-fasting group followed an eight-hour window that began after 1:00 p.m. Participants in the self-selected group chose their own eight-hour schedule.

The researchers measured body weight, fat mass, and fat-free mass before and after the intervention. One year after the program ended, they repeated the same measurements. The study was part of a broader research project whose key findings were published in Nature Medicine. These findings showed that participants who practiced TRE lost an average of 3–4 kilograms more than those who received only dietary counseling—regardless of when their eating window occurred.

Weight Changes Persisted Even After the Program Ended

Dr. Alba Camacho Cardeñosa, a researcher at the Joint Institute for Sport and Health (iMUDS) at the University of Granada (UGR) and a postdoctoral fellow at ibs.GRANADA in the Department of Endocrinology and Nutrition at San Cecilio University Hospital, is the study’s first author. She explains: “Although we knew that intermittent fasting promotes moderate weight loss in the short term, it was unclear whether these effects would last over a longer period. By following up with participants 12 months after the end of the intervention, we were able to demonstrate that the changes in body weight are sustained.”

The researchers also point to evidence suggesting that this method can be implemented outside of a controlled study. They emphasize: “A very positive finding is that one in three participants decided to continue intermittent fasting on their own during the one-year follow-up period, which suggests that it is a habit that can be integrated relatively easily into daily life.”

A Flexible Approach to Weight Management

According to the research team, even a 12-week period of intermittent fasting could be an effective medium-term option for weight management in overweight or obese adults. Since both early and late eating windows yielded lasting benefits, patients may be able to choose the schedule that best fits their daily lives. This flexibility could make it easier to adhere to the approach and potentially enhance its benefits in the treatment of obesity.

The MP20 group “Biomarkers for Metabolic and Bone Diseases” at ibs.GRANADA investigates biological markers and potential treatment targets related to metabolic, bone, and cardiovascular diseases. The group combines bioinformatics with clinical research to develop diagnostic tools and evaluate potential therapies. Its tasks include investigating intermittent fasting as a treatment for obesity and related health problems, as well as exploring whether bone markers can help predict cardiovascular risk. Through its multidisciplinary and collaborative approach, the group strives to produce research results with practical clinical applicability.

Why Researchers Want to Continue Investigating Intermittent Fasting

Although intermittent fasting has gained significant popularity in recent years, many long-term questions remain unresolved. Researchers continue to investigate for which people this dietary approach is particularly suitable and what biological mechanisms underlie the observed effects. An important area of research in this context is chronobiology—that is, the science of the body’s natural rhythms and their significance for metabolism, hormones, and health.

The human body follows an internal clock that controls numerous processes, including the sleep-wake cycle, hormone release, body temperature, digestion, and energy metabolism. The way the body processes food also changes throughout the day. Studies show that metabolism is often more active in the morning than in the evening: the body can often process nutrients more efficiently earlier in the day, while late meals may be associated with less favorable changes in blood sugar and insulin levels.

For this reason, scientists are increasingly investigating not only how long people fast, but also when they eat. Earlier eating windows, in which food intake occurs primarily in the morning and early afternoon, may better support the natural daily rhythm of metabolism. However, other studies show that later eating windows can also offer benefits, especially when consistently adhered to. The key, therefore, may be to find a form of intermittent fasting that is both biologically sound and feasible to implement in daily life over the long term.

Further research should also clarify which groups of people benefit most from this method. Some people have great difficulty counting calories or controlling their portion sizes over the long term. For them, a time-limited eating window could offer a simpler structure, as it requires fewer decisions about specific foods or quantities. “Future studies should focus on identifying individuals who have difficulty improving their eating habits, as they may achieve better results with intermittent fasting diets, thereby enabling more personalized weight management,” said Professor Heilbronn. Research is thus increasingly moving away from the question of which diet is fundamentally the best. Instead, the focus is shifting toward an individualized approach: The most effective dietary strategy may be the one that aligns with a person’s biological makeup, daily life, and long-term habits.