JMIR Mhealth Uhealth. 2026 Jan 26;14:e58930. doi: 10.2196/58930.
ABSTRACT
BACKGROUND: Intermittent fasting emerges as a promising dietary approach against obesity, offering a cost-effective strategy for implementation via web-based platforms. We developed a Brief Online Intermittent Fasting Program (OIF), featuring a self-administered, weekly 1-day fasting regimen with replacement meals delivery, online guidance, and app messaging to support adherence.
OBJECTIVE: This pilot study aimed to assess the preliminary effectiveness, feasibility, and safety of the OIF on weight loss in adults with overweight and obesity in Japan. Secondary objectives were to assess its effects on body composition and metabolic markers.
METHODS: This 12-week, 1:1 randomized controlled trial recruited adults with overweight and obesity (BMI from 23 to <35) in 1 university, 1 hospital, and 2 company offices. Participants were randomized into 2 groups stratified by sex and age (<40 or ≥40 years). The intervention group received very low-calorie (407 kcal) meal replacements for weekly intermittent fasting, online guidance via Zoom (Zoom Video Communications, Inc), and app messages encouraging fasting and healthy lifestyles. The control group received app messages promoting healthy lifestyles only. Interventions were administered by a nonblinded researcher. The primary outcome was the change in body weight after 12 weeks, analyzed using intention-to-treat principles and adjusted for sex, age, and baseline weight. Secondary outcomes encompassed body composition, blood pressure, biomarkers (eg, hemoglobin A1c, triglycerides, and cholesterol), quality of life, physical activity, intervention adherence, and adverse events.
RESULTS: A total of 57 individuals were enrolled (28 in the intervention group and 29 in the control group). At 12 weeks, 25 participants in the intervention group and 27 participants in the control group completed follow-up. The baseline median weight was 75.8 (IQR 68.3-80.6) kg for the intervention group and 74.8 (IQR 69.8-81.8) kg for the control group. The mean weight change was -0.9 (SD 1.9) kg in the intervention group and +0.6 (SD 1.4) kg in the control group. The adjusted between-group difference in weight change was statistically significant at -1.6 (95% CI -2.5 to -0.8) kg. Fat mass change was not statistically significant (-0.1, 95% CI -1.3 to 1.4 kg), but muscle mass reduction was implied (-1.3, 95% CI -2.5 to -0.2 kg). Intervention adherence was 79% (22/28) in the intervention group. No serious adverse events were reported, and there were no significant changes in key biomarkers, such as hemoglobin A1c or quality of life.
CONCLUSIONS: The OIF demonstrated effectiveness in promoting modest weight loss among adults with overweight and obesity over 12 weeks, with high feasibility and safety indicated by low dropout rates and absence of serious adverse events. However, the observed reduction in muscle mass indicates a need for program refinement, such as incorporating exercise guidance, to optimize health outcomes.
TRIAL REGISTRATION: UMIN-CTR UMIN000050437; https://tinyurl.com/4x5h2t2x.
PMID:41587446 | DOI:10.2196/58930
