I regret to inform you that I am unable to come to work today. You see, I am suffering from a terrible affliction called Can't-Fit-Into-A-Damned-Thing-in-my-Closet. While I realize that this condition is not contagious, the terrible mood associated with it can be passed along quite easily and I would hate to spread that to the rest of the staff. Also, I am quite sure that you would not want me there wearing the one thing that does still fit me: my own skin. No, it would not be a good thing to sit at one's desk totally naked now, would it? I daresay it might frighten the clients!
Therefore, I feel it is in the best interests of all concerned if I spend some time alone at home, taking my misery out on the treadmill instead of yourself and my co-workers.
I know you'll understand. I'll see you in a couple of weeks when I am 5 pounds thinner and therefore able to squeeze my fat ass into something appropriate.