Bottom line: its OK to indulge once in a while! Eating your favorite meal can help keep you motivated. (But contrary to popular belief, cheat days dont boost your metabolism). Any sudden weight gain is not fat.
Why do you gain weight after a cheat day?
This is caused by increased levels of leptin, a hormone secreted by fat cells and responsible for maintaining energy balance in the body. After eating a larger meal than usual, your body increases leptin production by as much as 30 percent for up to 24 hours.
How often should you have a cheat day when trying to gain weight?
There is no specific guideline for when or how frequently your cheat meal or day should occur. Often people will include one cheat per week, but this can change depending on what the persons health or weight loss goals are.