As the annual bacchanalia that is the Danish julefrokost season creeps ever closer, a new US study is offering up a bit of cautionary advice: those extra kilos packed on during the holidays could be hanging around your waist long after the Christmas tree has been hauled to the dump.

Every holiday season carries its own fat bomb, but the Christmas season is by far the heaviest, and nowhere is it felt more acutely than in northern Europe – not even in the US.

According to figures reported by videnskab.dk based on a study of 3,000 people from different countries, Germans packed on 0.6 percent of their own bodyweight in the ten days leading up to Christmas, compared to 0.4 in the US and 0.5 in Japan.

Extending the numbers out to New Year’s Day, Germans added a full 1 percent of their bodyweight over the holidays, and the extra weight doesn’t come off easily or quickly. Danish holiday traditions are similar to those found in Germany, and in many cases even more fattening.

A moment on the lips, forever on the hips
The Americans in the study did not begin to lose their holiday weight until May, and they then started to slowly add on the pounds again when the holiday treats began their siren call the following October.

“Three different countries, but people from each one all gained weight during the holidays,” wrote Brian Lansink, a PhD at Cornell University in the US who is one of the authors of the study.

“To advise a patient to have better self-control during the holidays is one approach, but perhaps it would be better to tell them that half of the extra holiday weight they add will still be there come the summer or even longer. The less you gain, the less you have to lose.”

READ MORE: Under the Raydar | Surviving the Danish Christmas

The study has just been released in the New England Journal of Medicine.