It's all down to math at the end of the day. To pack on one pound of fat, you need to consume 3,500 more calories than your burning. So to gain 1 pound a week you'd need to eat another 500 calories on top of what you're already eating.
At this rate of gain it would take around 1 year to gain 50lbs, obviously if you want to gain quicker you have to eat more or cut down on exercise
At this rate of gain it would take around 1 year to gain 50lbs, obviously if you want to gain quicker you have to eat more or cut down on exercise
10 years