Abstract

Background: Intermittent fasting (IF), particularly the 16:8 method (16 hours of fasting followed by an 8-hour feeding window) has gained widespread popularity as a strategy for weight loss and improved well-being. Its increasing prevalence among young adults has sparked debate within the scientific community regarding its actual efficacy. While existing literature supports its physiological benefits, including metabolic switching and improved insulin sensitivity, most findings are based on animal models. The evidence supporting its sustained benefits in humans, especially in the short term, remains inconclusive and underexplored. Moreover, concerns have emerged about IF's psychological impact, such as increased risk of binge eating, mental fatigue, and dietary dissatisfaction. This study aims to fill a gap by examining the short-term effects of IF in a human sample, evaluating both physiological outcomes and psychological responses.

Method: To investigate these short-term effects, this research studied 22 young Thai men aged 18–25 years, all with an endomorphic body type and sedentary lifestyle. Participants were divided into two groups: a control group and an experimental group that practiced IF using the 16:8 method. Both groups originallhy consumed their maintenance-level calories, tracked through the MyFitnessPal® application. Body weight was measured daily over a four-week period, and BMI was recorded weekly. Quantitative data were analyzed using Welch Two Sample t-Tests and time- series analysis via R Studio. At the end of the study, a qualitative survey evaluated factors such as satisfaction, hunger, cravings, mental and physical exhaustion, and binge-eating tendencies. The Kruskal-Wallis Rank Sum Test was used to compare responses between the two groups.

Results: Quantitative findings revealed that both groups experienced a reduction in weight and BMI over the four-week period. However, the mean difference in weight loss and BMI between the control and experimental groups was not statistically significant (p = 0.4302 for weight; p = 0.5282 for BMI), suggesting that caloric deficit (regardless of the timing of intake) was the primary factor influencing weight loss. This finding challenges the perception that time-restricted eating alone yields superior weight reduction outcomes. In contrast, qualitative outcomes demonstrated significant discrepancies between groups. Participants in the IF group reported greater mental and physical exhaustion, higher instances of cravings and hunger during fasting periods, and an increased tendency toward binge eating. Notably, overall research satisfaction was significantly lower among those who practiced intermittent fasting (p < 0.001). These results point to a potentially detrimental psychological impact of time-restricted eating patterns, especially when applied in a short-term, unsupervised context.

Conclusion: This study concludes that while IF may appear beneficial for some individuals, its short-term implementation does not yield statistically superior weight loss compared to traditional caloric restriction alone. Moreover, it may introduce undesirable side effects related to mental well- being and eating behavior. Given the narrow participant demographic and short study duration,further research with a more diverse population and longer observation period is recommended to substantiate or refute the broader applicability of IF. Until then, practitioners and the general public should be cautious in interpreting the benefits of IF and consider both its physiological and psychological impacts before adopting it as a lifestyle change.