On average, people gain 5 lbs (2 kg) in the four-week Christmas period,'' says Ursula Arens, spokesperson for the British Dietetic Association. "Trying to lose weight at this time is totally ridiculous and socially unpleasant. You just need to aim for stability."

The Christmas meal is not the biggest problem. You can cut calories by choosing white turkey meat, removing the skin (saving about 50 calories per portion) and stacking high the unbuttered veggies but where's the fun in that? To put on 1lb of body fat you need to eat an extra 3,500 calories – not that hard to achieve on Christmas day. But one blow-out meal will not push you up a dress size. The real issue is the weeks of abandonment on either side.

"The overall average weight gain works out at just an extra 500 calories a day," says Elisabeth Weichselbaum of the British Nutrition Foundation. That is the equivalent of a mince pie and a few extra glasses of wine. Parties, then, are the major calorie hotspots. Drinking wine instead of cocktails or creamy tipples such as Baileys can help to keep things under control. Alternating each alcoholic drink with a glass of water is another good moderation trick. You can also add fizzy water to white wine for spritzers that last longer with no extra calories.

Of course, drunkeness lowers the inhibitions and while the word "nibbles" may sound innocent party food can be disastrous, according Weichselbaum. "You can easily consume the equivalent of a whole meal just in canapés," she says. With snacks, she advises sticking to the one handful rule (one handful of crisps or nuts, then stop). And be strict with your canapés - avoid ones with creamy toppings or pastry bases. Allow yourself one or two others, then stop.

Living among mega-sized tins of chocolates can also be catastrophic for the waistline. Arens suggests "a glorious sweet eating time" once a day where you open the tin, scoff a few, then put it on the top shelf until the next day. This avoids unconscious grazing, where you consume a chocolate factory's worth in front of the TV without really noticing.