The aim of this study was to evaluate the effects of aerobic training in a fasted versus a fed state during Ramadan on body composition and metabolic parameters in physically active men. Nineteen men were allocated to 2 groups: 10 practicing aerobic training in a fasted state (FAST) and 9 training in an acutely fed state (FED) during Ramadan. All subjects visited the laboratory for a total of 4 sessions on the following occasions: 3 days before Ramadan (Bef-R), the 15th day of Ramadan; the 29th day of Ramadan (End-R), and 21 days after Ramadan. During each session, subjects underwent anthropometric measurement, completed a dietary questionnaire, and provided fasting blood and urine samples. Body weight decreased in FAST and FED by 1.9% (p<.001) and 2.6% (p=.046), respectively. Body fat percentage decreased only in FAST by 6.2% (p=.016). FAST experienced an increase in the following parameters from Bef-R to End-R: urine specific gravity (0.64%, p=.012), urea (8.7%, p<.001), creatinine (7.5%, p<.001), uric acid (12.7%, p<.001), sodium (1.9%, p=.003), chloride (2.6%, p<.001), and high-density lipoprotein cholesterol (27.3%, p<.001). Of these parameters, only creatinine increased (5.8%, p=.004) in FED. Creatinine clearance values of FAST decreased by 8.9% (p<.001) and by 7.6% in FED (p=.01) from Bef-R to End-R. The authors conclude that aerobic training in a fasted state lowers body weight and body fat percentage. In contrast, fed aerobic training decreases only body weight. In addition, Ramadan fasting induced change in some metabolic parameters in FAST, but these changes were absent in FED.