Summary:
This study is a randomised controlled trial that compared intermittent fasting with early time-restricted eating (iTRE), continuous calorie restriction (CR), and standard care in adults with obesity and metabolic risk. It looked at weight loss, and how these approaches affected eating habits, mood, sleep, and quality of life, and whether changes in eating behaviour helped explain the results. Lifestyle approaches are commonly recommended as the first step for managing obesity, but long term adherance can be challenging. How people relate to food plays a big role in success, especially dietary restraint (how much someone consciously controls their eating) and dietary disinhibition (tendency to overeat when triggered by hunger, emotions, or environmental cues). These behaviours are also shaped by mental health and sleep, and often matter more for long-term weight loss than the specific diet plan itself. The study included 209 adults who were randomly assigned to one of three groups: intermittent fasting with early time-restricted eating, calorie restriction at 70% of energy needs, or standard care. Both diet groups received regular support from health professionals, while the standard care group only received general healthy eating advice. Participants were followed during a 6-month intervention period and then again 12 months later. Both intermittent fasting and calorie restriction led to more weight loss than standard care at 2 and 6 months. However, the way they influenced eating behaviour was different. Calorie restriction was linked to greater improvements in eating control, including stronger dietary restraint and lower levels of overeating and hunger, compared with the other groups. Interestingly, while restraint increased, it didn’t directly explain the weight loss results. Instead, reductions in overeating behaviour (disinhibition) helped partly explain the weight loss in the calorie restriction group, accounting for about 15% of the effect. Overall, both approaches were effective for weight loss, but worked in slightly different ways. Calorie restriction was more closely linked with reducing overeating patterns, while intermittent fasting achieved similar weight loss without the same level of change in eating behaviour.
Abstract:
Background and aims: Psychological and behavioural effects influence diet adherence and mediate the effectiveness of lifestyle interventions but are poorly studied with intermittent fasting approaches. Therefore, we compared the effects of intermittent fasting versus calorie restriction on eating behavior, mood, sleep, and quality of life after 6 months and 18 months.
Methods: This is an exploratory analysis of a randomized controlled trial with 6-month intervention and 12-month follow-up. Adults (n = 209, 57% female; 58 ± 10 years, 34.8 ± 4.7 kg/m2) with obesity were randomized to one of three groups (2:2:1): (i) intermittent fasting plus early time-restricted eating (iTRE, 30% energy requirements between 8am and 12pm followed by 20-h fasting three non-consecutive days, non-restricted on other days), (ii) calorie restriction (CR, 70% energy requirements), (iii) standard care (SC). Both iTRE and CR groups received nutritional support biweekly, whereas SC was provided healthy guidelines at baseline only. Eating behaviors, mood, sleep, mood and quality of life were assessed using validated questionnaires at month 0, 2, 6, 18. Mediation analysis was performed to examine the relationship between eating behavior and weight loss at 2 and 6 months. Results: Greater weight loss was observed in iTRE and CR versus SC at month 2 and 6. However, greater increases in dietary restraint were observed in CR versus iTRE and SC at month 2, 6 and 18. Greater reductions in disinhibition and feelings of hunger were also observed in CR versus iTRE and SC at month 6. There was no detectable mediation effect of change in dietary restraint on weight loss, but disinhibition appeared to mediate the effect on weight loss in CR, accounting for 15% of the total treatment effect.
Conclusion: Both intermittent fasting and CR effectively induce weight loss, but they potentially act through distinct behavioural pathways, with disinhibition playing a more prominent role in CR.
Article Publication Date: 15/05/2026
DOI: 10.1016/j.clnu.2026.106686
