This quasi-experimental study investigated the effects of 8 weeks of Monday-Thursday Sunnah fasting on fecal short-chain fatty acids (SCFA), fasting total GLP-1, appetite regulation (hunger and satiety area under the curve), dietary intake, and body composition in obese adult males in Indonesia.

Monday-Thursday Sunnah fasting is a twice-weekly Islamic religious practice involving complete abstention from food and water (dry fasting) from dawn (approximately 04:30) to sunset (approximately 18:00), approximately 13 hours per day, practiced by millions of Indonesian Muslims. Unlike conventional intermittent fasting protocols, Sunnah fasting is motivated by religious observance, which may enhance adherence.

Seventy-four obese adult males were enrolled (intervention n=38, control n=36). The intervention group performed 16 fasting days over 8 weeks without any caloric restriction outside fasting hours. Fecal SCFA were measured by GC-MS; fasting total GLP-1 by ELISA; appetite by Visual Analogue Scale (VAS); dietary intake by 24-hour recall; and body composition by bioelectrical impedance analysis.

Primary analyses used linear mixed models (LMM) controlling for baseline differences arising from the sequential allocation design.

Intermittent fasting (IF) has emerged as a strategy to favorably modulate gut microbiota and short-chain fatty acid (SCFA) production in obesity. However, most published protocols involve wet fasting (caloric restriction with ad libitum water), which is mechanistically distinct from dry fasting. Monday-Thursday Sunnah fasting, an established Islamic practice, involves complete abstention from food and water (dry fasting) for approximately 13 hours twice weekly.

This study was conducted at the Faculty of Medicine and Health, Universitas Muhammadiyah Jakarta, from October to December 2025. Eligible participants were obese adult males (BMI ≥ 25 kg/m², waist circumference > 90 cm) aged ≥ 19 years, with no recent history of antibiotic use, probiotic supplementation, or other IF practice.

Recruitment was performed sequentially: eligible participants were first assigned to the intervention group until quota was met; subsequent eligible participants were assigned to the control group. LMM was adopted as the confirmatory analysis to account for significant baseline group differences resulting from this design.

The intervention group performed Monday-Thursday dry fasting for 8 consecutive weeks (16 fasting days total). No dietary restrictions were imposed outside fasting hours. The control group maintained habitual diet and lifestyle.

Outcomes were assessed at baseline (Week 1) and endpoint (Week 8), with appetite and dietary intake also assessed at Week 4. Primary laboratory analyses (SCFA by GC-MS, GLP-1 by ELISA) were conducted at Prodia Clinical Laboratory, Indonesia.

Inclusion Criteria:

• Male, age ≥ 19 years
• BMI ≥ 25 kg/m² (Asia-Pacific obesity criteria)
• Waist circumference > 90 cm
• No regular intermittent fasting practice in the prior month
• No antibiotic use in the prior month
• Not currently enrolled in any dietary or weight loss program
• Muslim and willing to perform Monday-Thursday Sunnah fasting
• Residing in DKI Jakarta and surrounding areas (Bogor, Depok, Tangerang)

Exclusion Criteria:

• Diagnosed type 2 diabetes mellitus on oral antidiabetic agents, insulin, or GLP-1 receptor agonists
• Coronary heart disease
• Chronic kidney disease
• Uncontrolled hypertension
• Regular use of probiotics, prebiotics, fiber supplements, omega-3, or herbal supplements
• Regular use of lipid-lowering agents, orlistat, appetite suppressants, or hormonal medications
• Excessive alcohol consumption
• Vegetarian diet
• Active smoker