Why Christmas is fattening, and how to counteract its effects (while still having fun)

The most fun and indulgent period of the year is here. It’s the time for relaxing, socialising, and celebrating. Irritatingly, it’s also the time of year responsible for much of our annual weight gain. Weight that becomes increasingly difficult to shift. Weight that accumulates. But, it’s not really our fault. We’re hard-wired to eat more and move less. And in the season of unabashed abundance, this makes us overeat, store fat, and keep hold of it. Fortunately, there are ways to work with our biology, to ensure we (and our children) have an enjoyable, healthy, and less fattening Christmas.

Mine’s a pint of honey.

During the upcoming festive period, we should raise a glass to our ancestors. Not just the close family members who are no longer with us to celebrate, but also our ancient relatives, without whom our species wouldn’t be what it is.

We’re here today because our forebears were specialists (the best, in fact) at eating more and moving less. More energy meant more offspring. So, natural selection forged humans with an incredible ability to crave, find, and overeat the highest calorie, most convenient food available, and then efficiently store, and ferociously defend, any excess calories (1). These clever evolutionary adaptions, however, are now starting to work against us. They’re the reason why both adults and children in our modern society are getting fatter and sicker (2).

As it turns out, the extended Christmas celebrations (and other periods of happy indulgence), is where biology and environment crash together most impactfully to conspire against our waistlines. Many of us put on unwanted weight in December (and often during our summer holidays as well). Between these periods of excess, we don’t usually gain any weight. But, crucially, we don’t lose it either (3). Which means there’s a gradual accumulation of body fat over the years.

But why is it so easy to pile on the pounds in December? Why is it so hard to lose them afterwards? And how can you break the cycle and avoid the holiday weight gain, while still enjoying Christmas?

The season of plenty.

Our body weight increases when the calories consumed from food and drink exceed the calories expended for maintaining life and fuelling activity (4). Annoyingly, most of the weight gain is fat (unless you’re body building) (5). While calorie consumption and calorie expenditure are both important, the former is the more influential, particularly during the upcoming festive period. It’s unlikely that anyone actively tries to overeat, but the environment we create induces us, nonconsciously, to do just that.

The run-up to Christmas is characterised by eating out, drinking, and partying. At least for the adults. Cake, chocolate, and sweets flow more freely for adults and children alike. The Christmas holidays are awash with fabulously indulgent meals, never-ending snacks, and the ubiquitous Christmas treats. It’s hard to go anywhere without bumping into piles of Christmas cake, mince pies, and selection boxes. And then there’s the booze. The standard stuff like beer, wine, and prosecco are consumed in copious amounts throughout, of course. But other more niche tipples, like sherry, slow gin, and Baileys, get their annual outing, and seem to create a veneer of acceptability to morning drinking.

When our primitive human brain is exposed to these stimuli, no amount of rationality, willpower, or restraint can prevent the gluttonous frenzy. The calorie-dense, highly pleasurable food causes dopamine to spike in the brain, overriding normal appetite regulation (6). The sheer variety of appearances, flavours, and textures in meals, snacks, and treats creates a “buffet effect”, which switches off feelings of fullness (7). Larger package and portion sizes, and having nibbles, chocolates, and sweets on display and within easy reach, give powerful visual cues and reduce the effort of acquiring calories (8, 9, 10). Each of these factors, independently, makes us overeat. In combination, they turn us into gannets.

Late-night merrymaking with friends and family, and early morning wake-up calls from young children, combine to shorten our sleep. The cumulative sleep deficit makes us hungrier the following day, crave more fattening foods, become more impulsive, and ultimately eat more calories and gain weight (11, 12).

Now, let’s talk about alcohol. There’s no need to be puritanical about it. But you should be aware of the roles alcohol plays in all this. Firstly, alcohol is an extremely rewarding substance, which is why it’s so addictive (13). It also brings a bunch of calories with it. For example, a large glass of wine and a pint of beer both contain over 200 Calories. And because of the sublime dopamine hit, it’s hard to have just one. Or just 5, for that matter! As you know, we don’t eat less food to make room for the liquid calories. In fact, alcohol stimulates hunger, and increases food intake (14). It also directly contributes to sleep disturbance, by reducing REM sleep and making sleep more fragmented (15).

The unstoppable lizard brain.

Your level of body fat is tightly regulated by a system referred to as the ‘lipostat’ (which resides in a region of your brain called the hypothalamus). It controls body fatness in the same way your internal thermostat controls body temperature (which also resides in your hypothalamus, by the way). We all have a body fat ‘setpoint’, a level of fat which your brain wants to maintain. If your body fat level falls below the setpoint, your primitive brain aggressively tries to get the fat back, by reducing your metabolic rate (16), making you voraciously hungry (17), and increasing the reward you get from food (18). This starvation response was a crucial survival mechanism in times of food scarcity, but it works against us in today’s environment.

Eating calorie-dense, highly pleasurable food (as we do at Christmas) causes nonconscious overeating, fat gain, and a ratcheting up of your body fat setpoint. This means your brain then defends a higher (and higher) level of body fat. Whether you’re emaciated or obese, any attempt at fat loss is met with the ferocious starvation response. It’s like fighting a lion. You can’t win. It’s why most calorie-restrictive diets are unsuccessful in the long term.

Maintain your setting.

In order to prevent our annual fattening, we need to focus on strategies that properly regulate appetite, mitigate any calorie excess, and turn down (or at least don’t turn up) our body fat setpoint. Here are nine recommendations to try this year:

  • Eat minimally processed food. If there is only one recommendation here that you put into action, make it this one. Eat food as close to its natural state as possible to regulate your appetite properly (19). Think home-made, rather than bought (e.g. proper gravy vs granules). Whole foods rather than refined (e.g. high-quality dark chocolate vs Celebrations). Simple rather than complex (e.g. grilled steak vs cheese burger with bacon, mayonnaise, and ketchup).
  • Embrace the turkey. Higher protein intake will make you feel fuller (20), help prevent overeating, and bring down your setpoint (21). Prioritise meat and fish at lunches and dinners, choose eggs for breakfast over cereals and pastries, and avoid processed foods (which tend to be low in protein).
  • Limit variety. Focus on a smaller number of different foods. Both in individual meals and throughout the day. This has the added benefit of being more time efficient and less stressful (especially on Christmas day!).
  • Don’t supersize. Use moderately-sized plates for meals and don’t overload them. Avoid large packets of crisps, biscuits, chocolates, sweets, and treats. Serve them individually or in small portions (or not at all).
  • Put up barriers. Keep snacks and treats out of sight rather than on display. And make obtaining calories a little harder. This can be as simple as having to walk to a different room, open a cupboard, or shell a nut.
  • Stay active. Consistent exercise helps to use more calories, and the more you do the better (22). But it also helps stabilise your setpoint even if you do overeat (23). Ramp up your usual training routine if you have one. If you don’t, there’s no better time to start. Get the whole family out for regular walks, outings, and activities. Limit screen time for children and encourage more physical play.
  • Prioritise sleep. Adults require 7-9 hours of sleep, teenagers 8-10 hours, and younger school-aged children 9-11 hours (24). Give yourself, and your children, sufficient ‘sleep opportunity’, and make sleep and wake hours as regular as possible. Turn down the lights and avoid screens a few hours before sleep (25).
  • Go easy on the booze. Enjoy a drink or three. Just be aware of the effects. The best drinks are the first two or three (we all know that, really!). Thereafter, the returns diminish, so why not stop there? A good strategy is to have a few drinks before and during dinner, then stop. This will limit calorie intake and allow at least some of the alcohol to be metabolised before bed, enabling better sleep.
  • Enjoy yourself. It is Christmas after all.

Give some or all of these a try. Experiment a bit. See what works for you. If you do overindulge and end up with a few extra kilograms come January, don’t despair. Incorporating these recommendations in the new year will help to turn down your setpoint, appease your lipostat, and enable you to lose the extra fat. But remember, prevention is easier than cure.

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