When preparing your own side dish, you might make the equivalent of a medium order of french fries. When you visit a fast food establishment, however, the clerk suggests that you upgrade your order for a nominal amount–perhaps a dollar–and receive twice as much food. This sounds like a good deal, so you spend a little more, and eat a lot more.

The problem with this equation is that spending more on one perishable meal, even if you receive exponentially larger portions, doesn’t reduce your spending later in the day. Nor are you actually more satisfied by the meal. Consider whether or not these “deals” are helping you save. If you split a larger portion with a friend, or if the food is one you can save and eat later, take advantage of the padded portions; otherwise, pass.