Being underweight has always been a problem for me. In fact, some months ago, I wrote a column lamenting the travails of being over-skinny.

As far as I know, most of the people who read the article did so without comment. But one of my friends sent me a warning e-mail in response.

'You ah, complain about nothing, you're just tempting fate,' she said. 'One day this will come back and bite you in the ass.'

That day has now arrived.

It came a few weeks ago, to be precise, when I woke up to discover that I could no longer fit into my pencil skirts and skinny jeans.

My behind had indeed swelled - not from any sting by destiny, but from something much more prosaic than that.

Marriage, it turns out, is making me fat.

Of course, I'm not saying that I went from a size XS to a size XL overnight nor is the excess weight (largely) visible.

But I've put on three stubborn kilograms that won't disappear, not even when I gingerly weigh myself in the morning after skipping supper the night before.

These days, when I sit down, there's a small but growing bulge that insists on making its embarrassing presence felt.

At a wedding I went to recently, I spent the whole night standing in creative poses to cover up my stomach, which was straining against a tight bandage-like dress I'd bought months before while still complacently skinny.

Some other clothes, like the abovementioned pencil skirts, have already had to be thrown away after I accidentally ripped them in a desperate attempt to pull up the zippers.

I'm keeping the skinny jeans, though. As motivation.

The marriage weight gain has come as quite a shock to me, not least because I've always managed to wiggle my way out of other well-known pound-piling situations in life.

In university, I dodged the infamous Freshman 15 - that refers to pounds, not classroom subjects - by balancing pizzaheavy study groups with regular trips to the university gym.

When I started my first job five years ago, I also steered clear of Work Weight - mainly because I was too stressed to snack at my desk.

I even escaped the notorious Break-Up Bloat, after a particularly wrenching end to a relationship a few years ago. That was thanks to the Depression Diet, the most effective weight-loss regimen ever.

But now, just when I was least expecting it, I have finally fallen prey - to the dreaded Marriage Flab.

Lest you think I just made that up, let me assure you it is a real phenomenon.

An article in the New York Times a few weeks ago cited a study that showed women who live with a partner tend to accumulate more kilos than those who live alone - giving new meaning to the phrase 'love handles'.

A somewhat less scientific poll I took of my peers also backs this up. For some reason, both male and female friends I know who have moved in with their partners or spouses have become a bit more, well, generously proportioned.

More than once, I've made the cardinal mistake of wondering out loud whether a recent bride is expecting a new addition to the family - and whether her husband is putting on sympathy weight.

The New York Times report didn't offer any reasons for Marriage Flab, but I have plenty of my own suggestions.

First, there's the Pantry Paunch.

Newlyweds moving into their own home for the first time always go a bit crazy stocking their kitchens with guiltfilled, calorie-heavy munchies.

They're too lazy to cook, so they substitute three balanced meals with unhealthy CRAP: Cheetos, Ruffles And Pringles.

Then there's the Stay-At-Home Sag.

Once you start cohabiting with your partner, you forego those long, romantic, and - most importantly - healthy walks on the beach.

Instead, your idea of date night is to sit on the sofa and watch TV for hours on end. While gobbling down Cheetos, Ruffles and Pringles.

But for me, the ultimate cause of Marriage Flab is simply the knowledge that someone else is happily getting fat along with you.

This gives rise to gleeful but gross relationship games such as Blissful Belly, where both of you start poking at each other's expanding waistlines and laughing at how tubby you're getting - and how little you care.

One of my colleagues, however, has a different take. 'Before I got married, I used to live on love and fresh air,' she told me the other day.

'Now, it's a different story. Does your husband offer you as much comfort as, say, a nice hot bowl of noodles?'

Mine still does, very much so. But that doesn't mean I'll give up the noodles.

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This article was first published in The Straits Times.