There are many things to be joyful about at Christmas: family gathered to the proverbial bosom; cloudy breath on icy air; streets glittering after dark; the scent of roasting chestnuts; hearty weekend lunches that give way seam-lessly to giddy evenings; the anticipation of a party, spiced booze that packs a punch; chocolate, chocolate, chocolate. For just these few dark weeks of the year, it's OK to drink at lunchtime, to share stollen over the photocopier, not to hold back on the petits fours. So bring me mince pies, all buttery and crumbling, and an extra chunk of Stilton with a good dollop of chutney on the side.

Yet herein lies a problem: while the shops dare us to bare our backs, arms and cleavages in the goose-pimpled dark of a party, we wake every morning to a dirty truth. Seasonal plumpness, jolly jelly, mince-pie mass, call it what you will: at Christmas we all put on weight, and it makes us feel rotten. The zipper breaks on the sparkly dress that you couldn't resist in September, your tummy rolls over the waistband of a favoured pair of skinny trousers, upper arms lodge, sausage-like, in your skinny rib poloneck. There's enough to feel bad about in January - credit card bills, boring food, boozeless nights - without hamster cheeks. Of all the balances to find in this precarious world, enjoying every delectable mouthful of Christmas without it making you miserable in the long run is one of the most delicate.

To avoid that buy-now-pay-later misery, you need to exercise damage limitation. A good start is to manage your expectations better. Don't try to lose weight. Don't buy that dress that's a smidge too tight, promising you'll drop a pound or two in the next couple of weeks. You won't. If there's a ripple around your bra now, there will be a fold by Christmas: buy a new bra and smile on. Because most of us live in fear of fat and spend our lives (theoretically) on a diet, simply trying not to put on weight means party time. Hello champagne, hello cocktails, hello canapés.

To many, booze and eats are the essence of the season; to others, they are the fat axis of evil. When else do people bother sizzling sausages and mulling wine, hanging gingerbread men and rolling chocolate yule logs? Who else, apart from moi, is that family tin of Quality Street for? However much you swear you won't, you will. A glass of champagne straight after work sharpens your hunger; a handful or five of crisps makes you thirsty. Free food and booze for weeks, and that's before the eating begins. And in the pit of your full tummy lurks the knowledge that January is just around the corner, and you will be back in your fat pants with nothing but your new gym membership to look forward to.

Why wouldn't we consume canapés at a drinks party? Cute little things, irres-istible when warm, so easy to pop in the mouth to fill an awkward gap in conversation and wash down with a glass of wine or four. And that's before dinner. When the mini quiches come around again, it's hard to keep in mind that they are simply there to enable you to drink without falling over.

Try to think of them as props rather than feasts in themselves. Stick to the high-protein ones: seared fish, sushi, smoked salmon, quails' eggs. They will fill you up for a bit longer without being heaped with calories. Better a small handful of nuts than a bowl of crisps. While named “fat pills” in our household, they are at least good for you, and release energy slowly so you won't be hungry again so soon. If there's an option, munch on raw ones rather than salted: the salt will make you drink more and the cycle will continue.

It's classy to get beyond the “it's food, it's drink, it's free” mentality. Hoovering the whole plate will not make you less broke. If you have made a credit crunch bargain with yourself not to go out for dinner afterwards, make every other bite a vegetable-only one. If you're determined to get value for money, a good rule of thumb is that the more expensive the food (foie gras aside), the less fattening it is likely to be. Go, smoked salmon, Parma ham, out-of-season asparagus.

With booze, the golden rule is not to drink on an empty stomach. It may seem counter-intuitive, but having something in your stomach means you won't start gorging as soon as you're drunk enough not to care. The pecking order goes like this: wine over its mulled sister, champagne over wine, anything over beer. Clear drinks over coloured (which tend to have more sugar), and avoid creamy cocktails. Stay away from anything with lots of fizzy mixers; sugar packs it on. If this sounds boring, think of it in terms of hangover payoff: extra sugar not only makes you tubby, it makes your head bang harder, too.

To dinner itself. However tempting the bread basket looks to goggle eyes, bread is not a festive speciality, so why bother? Leave space for seasonal delights. Enjoy instead fragrant game birds roasted under their protective bacon jackets, steaming mounds of mashed celeriac, pools of glossy gravy. For pudding, what could be more appropriate than poached, spiced pears, or citrussy jellies, so fashionable again. By the time the truffles come around with coffee, truly, you will want only one. Take it from me, the second won't taste as good.

On the nights when you don't go out, offset. Don't drink at home, have a bowl of chicken soup, put a face pack on (it's hard to guzzle with mud on your T-zone) and go to bed early. You'll have more fun tomorrow.

Christmas Day should be about indulgence, not calories. But you're not obliged to wade through everything and you won't feel great if you do. Start the day with a good, filling breakfast of muesli or porridge, then try not to pick between meals. Don't be fobbed off with mulled wine; insist on champagne. Remind yourself regularly that chocolate coins are for decoration. Build a tower of turkey on your plate, pack it with brussels, roasties, stuffing, bread sauce and gravy. But don't go back for more. If you find plum pudding bearable only alongside double its volume in brandy butter, think again about how much of it you really want to eat. Feed it to the dog. Of course you should scoff mince pies, but consider this: perhaps five is too many.

And if it all goes to pot and you find yourself once again, like Bridget Jones, on the scales at New Year, don't feel glum. January wouldn't be the same without a detox.

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