How much weight can you realistically gain over Christmas?

Just in case that huge tinsel-covered tree in your local shopping centre wasn’t a big enough hint… Christmas Day is almost upon us, whether you’re ready for it or not.

Although your wish list may change from one year to the next, there are some aspects of Christmas that will never change.

These include: Mariah Carey's All I Want for Christmas Is You on loop (non-negotiable); the fight your uncle and your grandfather (substitute with family members as appropriate) will inevitably get into over lunch; and food. So much food. Piles and piles of it.

Michelle Bridges’ 6 tips for surviving the festive season.

With a lot of food comes a lot of eating. It's normal - nay, tradition - to throw portion control to the wind and gorge yourself on prawns, turkey, salads, fruit, puddings, chocolate coins, wine, champagne... etc etc etc on Christmas Day. And with so many parties and catchups over the 'silly season', we also tend to consume more than usual in the lead-up to December 25, and between Christmas and New Year's Eve.

There's nothing to feel guilty about here - food and drinks are a big part of what makes Christmas such a special event, so you shouldn't feel you have to deprive yourself that enjoyment. But you may be wondering: what exactly does this Bacchus-style festival of indulgence actually do to your waistline - and is there really any need to freak out about it?

According to Michele Chevalley Hedge, qualified nutritionist and author, and founder of A Healthy View, it's not uncommon for Australians to gain "a kilo or two" over the whole summer holiday season. That's not as much as you'd expected, right?

"[Consuming] an extra 500 calories per day over the holiday ... can lead lead to a half a kilo of weight gain per week," Michele explains. This 500 calories could take the form of a slice of pavlova, a few nibbles at your office Christmas party, a handful of lollies, a cocktail with a sweet mixer or a couple of glasses of wine.

Need a visual reference? Just multiply these by 2.5 and you've got 500 calories:

If the various reports and figures floating around the internet are to be believed, it's possible to eat upwards of 6000 calories on Christmas Day. The average daily calorie intake sits around the 2000-2500 mark, so, yeah... that's quite a lot more than usual. Michele says it's possible to gain a kilogram on Christmas Day, but you'd really have to gorge yourself.

"One kilo equals around 7,000 calories, which means if you burn 1,800 calories in a day, and if you consume more than 8,000 calories on Christmas Day you may end up gaining on kilo of fat," she says. How much is 8,000 calories? Well, you'd need to eat 500 grams of ham  (575 calories), two cups of potato salad (714), 20 large prawns (120), 4 Yorkshire puddings (216), 400 grams of turkey breast (756), 2 serves of Christmas pudding (184) with cream (586), and drink a whole bottle of champagne (495) at lunch. Then you'd need to sit down at dinner and do it all again. Finally, for dessert, you'd have to convince someone to drive you to the nearest McDonalds, where you would need to eat an entire Big Mac (550) and fries (220) to get over the 8,000 calorie line.

That doesn't sound like something you'd do, does it?

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In general seemingly gaining more than a kilo 'overnight' is usually the result of a number of factors, not just food intake.

"Ask yourself - do you have fluid retention from salty meals or too much alcohol? Are you constipated [or have] bogged-up digestion from holiday stress and some unhealthy food choices?" Michele says. Hormonal fluctuations around your period, and your hydration levels can also impact the number that appears on the scale.

If you do get a little heavier over the festive season, Michele there's no need to freak out and resort to some extreme diet to restore your weight to its previous state.

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"Usually the one to two kilo weight gain over the holidays will come off when we go back to our normal routine.  The people with the most success with weight loss are those that don’t do anything extreme. Maybe a mild cleanse or a low sugar, clean eating plan," she says.

If you're really concerned about how Christmas is going to impact your diet, Michele recommends increasing the amount of exercise you do, and 'choosing your poison'.

"If you're going to have some wine, then don’t eat the sausage roll or heavy carb, sugary foods," she says. "I suggest eating high protein, with lots of veggies and low sugar - this will keep your blood sugar from rollercoaster-ing, [and] creating sugar cravings."

What are you serving up this Christmas?