My partner is really cute. I don't mean to brag, but it's true. Craig was a skateboarder, football star and windsurfing instructor back in his uni days.
He proudly recounts, coffee-coloured eyes lighting up at the memory, that the girls at high school carved his name into the tops of their desks. And that he was actually listed on the wall of the girls' bathroom as one of the "top three hottest guys in school".

When I met Craig three years ago, he was 28, 175cm tall, and a hard-bodied 72kg, with a super-taut stomach and the kind of arms that aren't huge but can lift anything. A couple of years into the relationship, though, the same thing happened to him that happens to lots of guys when they turn 30. He got fat. Well, not fat exactly, but a little chubby, with jowls, love handles and a strange new appendage called a tummy.

At first I didn't mind too much. I'd rub Craig's belly - "My little Buddha," I'd say. He would laugh. He was so busy at his new job at a photography studio that he had started grabbing lunch at the fast-food joint on the corner. Every day. He left his active lifestyle at his old shared flat because he felt too busy to exercise, so his lunch went straight to his belly, which he jokingly began to refer to as his "capitalist gut". But sometimes when he said it, he looked really sad.

Stuffing it up

He was still the cutest, as far as I was concerned. I figured once his pants got too tight, he'd cut back on the kilojoules. Instead, he just stopped doing up the top button. He kept on buying Mars Bars and ending each dinner conversation with "Are you finished eating that?" In eight months he'd gained 10kg. It was clear that this new development in his life - you mean I can't eat everything I want and not gain weight? - had him really confused.

Every attempt I made to help him was completely fruitless. I'd make off-hand suggestions here and there, such as, "Popcorn with extra butter isn't a good snack," and, "Some people call white bread 'the white devil'." I cooked couscous instead of pasta. I tried taking him on walks after dinner, but he resisted like a petulant puppy. I hid the butter; he went to the supermarket and bought a family-size tub - which is hard to hide behind anything. When a security guard at a concert stopped him going in because he thought Craig had something stuffed up his shirt, I averted my eyes. Later, we had a mind-boggling late-night conversation about the concept of "dieting". I tried to explain that a diet meant eating salads, lean meats and a good breakfast. "But I've already started a diet," Craig said. "I don't eat breakfast." Oh no.

I think he picked up this idea at his office, where everyone was on some radical diet, such as eating only olives. He worked for a famous photographer and all the other guys in the office were gay. And gorgeous. And beginning to notice that the formerly hot straight guy was becoming not so hot. One day when I was visiting Craig for lunch at his work, the Botoxed, wheatgrass-fed, triumphantly fit in-house publicist confronted me in the hallway. "Your boyfriend is getting fat," he hissed.

I reeled. It was OK for me to realise that Craig was a little chubby, but another thing entirely for a stranger to notice.

"I know," I replied, in as non-confrontational a tone as I could possibly manage. "But what can I do about it?"

"Well, you could help him." Excuse me, but aren't I helping him already? I thought, fuming. What else was I supposed to do, babysit him on Atkins, parcelling out itty-bitty pieces of sirloin and Swiss cheese at specific intervals? It's not like any of my other boyfriends had helped me when I gained weight (or thought I had).

It's not about you

Once I was on the defensive, Craig and I started to fight. He said the reason he was gaining weight was because I didn't know how to cook. I said I felt like I couldn't get him to do anything - he didn't listen to me enough, whether I was advising him what to eat, filling him in on new developments in the Middle East or making him pick up his dirty socks. He said that I wasn't listening enough. I wasn't nurturing enough, he claimed. What exactly was non-nurturing about the way I'd been acting? "I don't want to be nagged," he said. "Nagging is not nurturing."

I guess I didn't know how not to nag when it came to food. I grew up in a Greek family who believed that, if you weren't eating every minute of the day, you must be sick. I realised I may have been acting a tad overbearing. Truth be told, I'd whine like a baby when I was trying to make Craig do something my way. In the back of my mind I began to wonder how much of my own self-worth was invested in Craig's appearance; that frisson I got from others' admiration when they first met him - "Nice job, Vanessa! Can I have him when you're done?" Instead of wanting him to get his six-pack back so he'd feel better about himself, maybe I wanted him to get it back so I'd feel better about me.

In the process of objectifying Craig a little, I'd approached his weight gain like any other personal problem: if I worked hard enough on it, I could make what I wanted happen. But caring for someone is completely different - it requires finding a delicate balance between backing him up and backing off.

Turning the scales

At a local garage sale a few weeks after our "discussion" about nagging, I watched stealthily from the sidelines as Craig discovered an old pair of scales buried under a pile of broken chairs. I held my breath and said nothing as he tapped at it with his foot to see if it worked. He brought it home and put it in the bathroom. And he weighed himself every morning from then on.

It was his relationship with the scales that really changed things. He set a goal for himself and was determined to get that machine to display the number he wanted to see. As soon as he started taking responsibility for his weight, he stopped fighting with me about playing nutrition consultant, and I became more comfortable making suggestions. I stuffed carrots in his pockets, took him on long hikes and jumped up and down when he got down to 77kg after a few months.

One morning Craig and I were lying around in bed when he looked at me sleepily. "You know," he said, poking at my stomach, "you're getting a little fat." And he was right! I had spent so much time thinking about him that I had stopped thinking about my own eating habits. He wasn't being mean: he was just being honest, and letting me know that he cared. I didn't mind at all.

Vanessa Grigoriadis is a contributing editor at Rolling Stone magazine. She married Craig and they now live in Hawaii, where they're both healthier than they've ever been.