Gaining

Gaining 2lbs a week

And your body does not usually convert all the calories you consume for your bodies use. I read that to gain a lb you actually need to consume an extra 5200 calories.
6 years

Gaining 2lbs a week

If you want to gain 2 lb a week, you will need at least an extra 10,400 calories per week over what your body burns.

So that is, in round numbers, an EXTRA 1500 calories a day, average.
6 years