Ha. I was wondering about this too.
I was convinced I had gained a significant amount of weight during the last couple of months of applications - though, mind you, I am petite so "significant" really means something like 5+ pounds. I've hit the gym maybe once a week during this time, though I'd hazard less, and I snack heavily when I am writing essays.
Turns out I haven't gained much at all. Maybe a couple of pounds? Not more than I would during a normal winter, anyway. No doubt my mother would have commented otherwise.
My guess is that all these nights staying in my apartment working on apps has resulted in far fewer dinners out on the town, and though I quickly blasted through my only bag or two of chips, I've barely left the apartment to buy groceries. It's been a lot of three-minute Thai Kitchen soups and microwave popcorn for me! Not exactly healthy but they won't fatten ya up either.
On a related note, all this staying in has actually helped me save a significant portion of the awful $1500+ in application fees I've spent. No shopping, restaurant dinners, beer tastings, vacation. And I'm frugal to begin with.