Your body has a "set point" that is resistant to this kind of disruption. If you gradually increase calories and do it regularly, that's how you gain weight. I

Your body has a "set point" that is resistant to this kind of disruption. If you gradually increase calories and do it regularly, that's how you gain weight. I remained slim despite eating some very rich restaurant meals every so often until I started drinking and eating similar food at home nearly every day.