Objective: To determine the change in caloric intake, physical activity, body mass index and sleeping pattern during Ramadan among doctors. Method: The longitudinal study was conducted at a public-sector medical university in Karachi from April to May 2020, and comprised healthy doctors of either gender who planned to fast during Ramadan. Data was collected using a multitude of validated structured tools by trained data collectors. Data was analysed using SPSS 20. Results: Of the 193 subjects, 103(53.4%) were females and 90(46.6%) were males. The overall mean age was 30.05±9.4 years. Caloric intake in the month before Ramadan was significantly higher 2288±495kcal/day than during Ramadan 2089±491kcal/day (p