I think you make an error by implicitly assuming that calories burned (2k/day) are constant even as the weight is being gained (~300lb/30yrs). I believe that th

I think you make an error by implicitly assuming that calories burned (2k/day) are constant even as the weight is being gained (~300lb/30yrs). I believe that the mass being gained does incur some caloric overhead. So if you begin eating 5% more calories than you should, you'll gain weight, but the rate will slow as the number of calories your body requires approaches the number you're consuming. Therefore you could have a stable weight, while still eating 5% more than you "should" be. All that said, I do hope someone corrects me if I'm wrong!