Our office shares a kitchen. Often food "disappears" despite being labeled, despite little notes that say something to the effect of "If you didn't bring it, don't eat it." I know who the culprit is --- how should I phrase my confrontation?

Kevin says:  Short answer, you don’t. Bring the situation to your manager (or HR director), privately outline your suspicions, and let him or her handle it. That’s what they get paid to do. If you feel that this is a problem that doesn’t rise to the level of managerial intervention, you’ll need to arrange for other food-storage solutions. The fallout from such a confrontation is not worth the feeling of one-upmanship you’ll get in the moment --- and could professionally backfire in your face. I once worked in an office where food disappeared from the communal fridge, from people’s private, labeled lunches, etc. The culprit, it turns out, was a food addict with multiple health and mental problems. Someone who routinely steals food probably has other problems that you don’t know about and aren’t equipped to handle (psychological, emotional, financial). My advice: leave it to the professionals.

Beth says:  This has happened to me everywhere--in my own home, in my dorm, and in every office I have ever worked in.  I'm a teacher, so I would have no option about taking it to a higher level.  My department chair and principal certainly don't have the time or inclination to deal with it and H.R. is in a totally different building!  Therefore, if taking it to the higher ups is isn't an option, here are a couple other ideas:

• Buy a small fridge for your office/desk area.  Many times, they have a key lock.  
• Don't have that kind of money?  Buy a nice lunchbox with an icepack that will keep things cool until you are ready to eat them. 
• Want to be more aggressive?  I can't think of a single way to do this without creating a work atmosphere that is infinitely worse than having your Diet Coke stolen.