Background:Many studies have shown various results regarding the effects of Ramadan fasting on weight and body composition in healthy individuals. Objectives: This study aimed to evaluate the effect of Ramadan fasting on body composition in healthy Indonesian medical staff.Objectives:In this study, we examined the influence of Ramadan fasting on body composition in healthy medical staff.Patients and Methods:The longitudinal study was performed during and after Ramadan fasting in 2013 (August to October). Fourty-three medical staff members (physicians, nurses and nutritionists) at the Internal Medicine Ward of the Dr. Cipto Mangunkusumo General Hospital were measured to compare their calorie intake, weight, body mass index, waist-to-hip ratio (WHR), and body composition, including body fat, protein, minerals and water, on the first and 28th days of Ramadan and also 4-5 weeks after Ramadan fasting. Measurements were obtained for all 43 subjects on the 28th day of Ramadan, but they were obtained for only 25 subjects 4 - 5 weeks after Ramadan.Results:By the 28th day of Ramadan, it was found that the body weight, BMI, body fat, water and mineral measures had decreased significantly (-0.874 ± 0.859 kg, P < 0.001; -0.36 ± 0.371 kg/m2, P < 0.001; -0.484 ± 0.597 kg, P < 0.001; -0.293 ± 0.486 kg, P = 0.001; -0.054 ± 0.059 kg, P < 0.001, respectively). Protein body mass and calorie intake did not significantly change (-0.049 ± 0.170 kg, P = 0.561; 12.94 ± 760.608 Kcal, P = 0.082 respectively). By 4 - 5 weeks after Ramadan, body weight and composition had returned to the same levels as on the first day of Ramadan.Conclusions:Ramadan fasting resulted in weight loss even it was only a temporary effect, as the weight was quickly regained within one month after fasting. The catabolism catabolic state, which is related to protein loss, was not triggered during Ramadan fasting. Further research is needed to evaluate the effects of weight loss during Ramadan fasting in healthy individuals.