How long does weight gain take after eating?
If you are in calorie balance, that is, your calories eaten
equal calories burned, you won't gain any weight at all. 3,500
calories equals roughly one pound of fat. Therefore, if you create
a calorie imbalance of eating 3,500 calories more than you burn
each week, you will gain about a pound of fat each week. So, it
happens pretty quickly. If you're talking about adding muscle, this
happens at a slower rate.