The Food Sensitivity Diet
Step 1: Start your morning with some sort of food that you're mildly allergic to. Like, say, a Liquid Nutrition Drink from your local Starbucks that tastes like blueberries but turns out (after it's all gone and you examine the label) to consist largely of apple juice. Sweet, deadly apple juice.
Step 2: After this, eat anything you want!
Step 3: And enjoy it while you can.
What you eat doesn't really matter, because eight to twelve hours later your body's slow discomfortable rebellion will come to a head and you'll---ahem---expel everything anyway. Besides which, the stomach ache starts almost immediately so you won't feel that hungry in any event. I do recommend, however, that you avoid eating anything expensive, unless you like the idea of throwing twenties into a cesspool.
Also, this diet works best for the unemployed, since you'll feel achy and you'll want to lie down and moan for several hours between trips to the bathroom. Don't operate heavy equipment or try any fine line drawing, as throughout the day your body will be racked with unpredictable shudders. And if you're traveling on the subway late at night (let's say you get on at 14th Street) and you're not sure how long you'll be able to hold out till 185th Street, it might be a good idea to pick up a discarded plastic bag lying on the seat next to you, just in case. If you time it properly, even if you have a sudden accident at, say, 96th Street, it may be possible for you to contain the damage so perfectly that you make no noise, your clothes remain spotless, and no one notices the funny guy with the bag over his mouth. Which is good, because if you're riding, say, the A express uptown, you may have to hold on to the filled plastic bag for about thirty blocks, pretending nothing's wrong, until the train stops at the next station and you can get to a trashcan.
This is all theoretical, of course. And I can claim that because---and I say it with some pride---no one noticed at all, and as I climbed aboard again at 125th, there was literally no indication that anything had happened or that I even felt unwell. (How fortunate that I always carry mouthwash!) I'm fine now, thanks. And I'm a few pounds lighter, if somewhat malnourished.