This water is expired

I am officed in a food pantry. I have worked here about six months now and have gained - oh, just hundreds - of pounds. That might be an exaggeration. Slightly. It feels, however, like God's own truth. I have been struggling to come up with good ways to make this phenomenon a nonphenomenon (new favorite thing to say, nonphenomenon nonphenomenon nonphenomenon). I have the following excuses:

• before I worked at Starbucks, which meant that I was on me feet, moving, and, more often than not, sweating several hours every day.
• working in a pantry means near constant access to cookies. And chips. And lemon bunt cake. And donuts. And sugary beverages.
  
• I have zero reasons to leave my desk during the day. Other than going to the bathroom.

So. Combating the phenomenon. What do I do? Obviously, ignore the free foods. Because, really, they aren't actually food at all. Secondly, get up every hour and run up and down the stairs a couple of times. Thirdly, I try to swim several times a week. In reality I swim about once a month. So, that one isn't really working. I have been considering replacing my desk chair with one of those exercise balls. I've heard that helps strengthen your core.

Dishearteningly, I think it has something to do with my illness. This is an abnormal amount of weight gain. Even more dishearteningly, it looks like exercise is the name of the game. Bleh.

I am taking suggestions for creative ways to be active in an office. Preferably without attracting too much attention.