My boyfriend sits me down, the corner of his right eye twitching slightly. "Can't you just stop dieting?" he says. "It's annoying. Honestly, really dull. And if you stop it'll be great. We can make plans. We can make meals together. It'll be much, much better."

I shrug. I know what he means. There's no doubt that dieting is unsociable. This is obviously true if you're a good dieter, since this involves turning down most lunch and dinner dates, and sitting at the table each night munching salad leaves while casting wry, piteous glances at the roast potatoes on everyone else's plates. The good dieter can quickly take on a sheen of self righteousness, not only making everyone feel slightly guilty by eschewing the flapjacks, but then making everyone feel really guilty by cataloguing the flapjacks' calorie count. This whiff of superiority is transient, arriving with the first blast of will power, and passing with the first major stumble. I know. I've experienced it. But while it lasts, it is extremely irritating for everyone else.

Even more annoying though, I suspect, is the unpredictability of the bad dieter. At least with the good dieter, you know where you are. You know there is no point inviting them for dinner. You learn not to offer them the chocolate cake. The rules are set, they are following them, and everyone else soon gets the picture.

But with the bad dieter, the rules are constantly shifting. My boyfriend never knows whether his offer to buy fish and chips is going to be met with hungry eyes and a wide smile, or "How can you even ask me that? I'm on a DIET!" Will the suggestion that we cook lamb shanks together be a popular one, or a hideous misstep? Every Sunday I go to the supermarket and stock up on enough diet-friendly food for myself to last the week, but that doesn't stop me looking at the risotto piled on my boyfriend's plate and saying: "I can't believe
you didn't cook any for me!"

I put a hand on his arm. "Just give me another month."