Munchies:
I also want to stress again that you should never switch jobs just to gain weight. If you like your job, it pays well, and you don't have a reason to switch jobs otherwise, stay where you are.
One of the reasons people get fat with sedentary jobs is stress. And the pay and benefits aren't always worth it.
Nofbar:
This. The job I had where I gained 100+ pounds had lots of food around, but it was burning me out.
Was the food provided by the company?