Holiday weight gain - how overeating and alcohol at Christmas and New Year can affect you

The Christmas-New Year period is a risky time for putting on unwanted weight - and studies suggest it can hang about. Photo / 123RF

It’s as much a part of the holiday period as pavlova and backyard cricket - you reach for those fruit mince pies and brandy snaps too often and wind up with a Santa belly. Should you worry? Jamie Morton explains.

How much of a big deal is holiday weight gain?

On average, people gain a small amount of weight – between 400g and a kilogram – each year.

While less is known about how much we pack on during the Christmas period specifically - findings from decades of studies range from a few hundred grams to several kilograms of holiday weight - it’s certainly something to be mindful of.

One study, published in the New England Journal of Medicine in 2019, suggests adults weigh more in February and March than they do in September and October of the previous year.

In another study published this year, a group of researchers found not just a pattern of weight fluctuations during the holidays but also a risk of that added weight lingering on.

Here in New Zealand – where we’re out at the beach, rather than snowed in and sipping mulled wine – less is known about the holiday bump.

One of Australia’s first studies on the topic, however, found participants tend to put on an average 564g over the Christmas-New Year break.

What’s the science behind it?

On one level, it’s quite simple: you consume more calories than you burn, and you put on weight.

UK research from 2016 found people cram in more than 5300 calories on Christmas Day: that’s twice the recommended daily average for men and three times that for women, but it mightn’t be so surprising if you consider a single fruit mince pie packs around 300 calories.

On another level, it’s a bit more complicated.

We all have an internal “food clock”, a collection of genes and molecules that interact to keep our bodies on an even metabolic keel.

Called the food-entrainable oscillator, it’s there to help us make the most of our nutritional intake, controlling everything from the absorption of nutrients in our digestive tract to their dispersal through the bloodstream.

On average, people gain a small amount of weight – between 400g and a kilogram – each year, and holiday periods like Christmas can bring a bump. Photo / 123RF

It can also anticipate our eating patterns.

Even before we eat a meal, we begin to turn on some of these genes and turn off others, preparing for the burst of sustenance – and that’s why we feel the pangs of hunger just as the lunch hour arrives.

But, by eating at odd times, or simply eating too much, we can destabilise that clock – putting on more weight in the process.

“A temporary period of over-eating can disrupt hunger regulation because it can lead to temporary desensitisation of the body’s natural hunger signals,” explains Dr Rajshri Roy, a registered dietitian and lecturer in nutrition at the University of Auckland.

“This might make it harder to recognise cues for hunger and satiety in the short term.”

Does holiday over-indulgence come with any long-term risk?

The good news, Roy says, is that for most people, hunger regulation normalises once our regular eating patterns resume.

In the short term, stuffing in too much food in one sitting could cause nausea, gas, and bloating.

“These symptoms occur as the digestive system is overloaded, working harder to process the excess food,” she says.

“While uncomfortable, these effects are generally not a cause for concern unless they persist or are severe, in which case consult a healthcare professional.”

Likewise, occasional over-eating isn’t likely to cause disease on its own.

“Chronic over-eating, along with poor diet quality, can increase the risk of chronic diseases like type 2 diabetes, heart disease, and certain cancers.

“The key is the pattern and regularity of overeating and the overall lifestyle and dietary habits. It’s not what you do sometimes, it’s what you do every day.”

Professor Michael Corballis, also of the University of Auckland, says the same applies for brain health.

“Over the longer term, overeating can lead to structural brain damage.

“But a few days to weeks of overindulgence is unlikely to have a serious long-term effect on brain structure or function in otherwise healthy people – and might even be a good antidote to stress.”

What else might make me pack on holiday weight?

Indeed, too much food isn’t the only factor behind holiday weight gain.

It’s also about what we’re eating: namely, calorie-laden foods that are high in fat, sugar and salt, and with little nutritional value.

Add to that the fact that our sleep patterns are often disrupted – which can boost hunger hormone levels and lower metabolism – as are our workout routines.

Then, of course, we have alcohol, which is typically high in those troublesome empty calories: a standard beer can pack about 150.

It also slows metabolism - hampering our ability to efficiently burn fat – while causing temporary weight gain through water retention, messing with sleep and sometimes stirring cravings for unhealthy food.

Turkey or chicken breast makes for a healthier Christmas option than salami or sausages.

For the brain, Corballis says the short-term effects of all that extra imbibing is similar to bursts of holiday binge-eating.

“While it’s probably true that there is no alcohol dose that can be described as completely safe, a brief period of low-level overindulgence, like a few holiday parties and summer barbecues, probably doesn’t pose huge additional risks to otherwise-healthy brains - as long as people take sensible precautions.

“As with overeating, it’s probably the baseline intake that is more important than a seasonal blip.”

How can I keep my weight on track through the silly season?

While the old adage of everything-in-moderation might be a tough ask with all those goodies about, it’s still possible to avoid starting 2024 with a bigger belly.

One tip is to eat intuitively: that means listening to your body’s hunger and fullness cues, choosing smaller plates, opting for a smaller variety of foods – and not going back for seconds.

Sometimes, it’s as simple as picking healthier treats – like turkey or chicken breast over salami, seafood over sausages, or roasted nuts over potato chips.

Self-monitoring also helps, as studies have shown, and there’s a galaxy of apps to help keep track of calories.

If you’re drinking, it’s a good idea to have a glass of water handy in between each pint or flute – something that’ll also help your head the next morning.

And, as if we should need reminding in the middle of a Kiwi summer, get out for a walk or a swim.