Let’s imagine for a moment that you’re in your local supermarket. For some reason or another, you completely forgot to eat before leaving home and now you have a craving for cookies. Now imagine you’re standing in the cookie isle and your eyes fix onto the chocolate chip ones. Before reaching for a packet, you have a brief moment of hesitation. “Am I really going to buy cookies? I really shouldn’t. I’ve been eating so well lately. I don’t want to backslide…” Your eye then shifts to the left a little, and you spy some low-fat chocolate chip-cookies that look equally appetising.