Now over time 250 adds up...
These excess calories usually are converted and stored in fat cells(fat cells hold stored energy). 1 pound of fat has roughly 3,500 calories, so stay in a hypercaloric state for 2 weeks you should gain about 1lbs(give or take).
Now you see how this works?
What about losing weight?
Well the opposite is called hypocaloric state(hypo meaning below base line aka basal), so given the same variables above a person who requires 1750 calories a day only eating about 1200 will be in a 500 calorie deficit should lose about 1lb a week High Performance Handbook