Overeating at Christmas can cause weight gain – but that doesn’t mean it’s permanent

The holidays are a time of indulgence, and many celebrations center around having festive food and drink. It’s no wonder that many people expect to gain weight at Christmas.

Indeed, many studies show that people can gain a few pounds during the holidays. But whether this weight gain is temporary or not depends on many factors.

First, it is important to note that our body weight varies greatly from day to day. Another study in three European countries suggested that adults were 0.35% more likely to have difficulty on a Monday than on the previous Friday.

This may be because people eat differently on weekends. Or it could be down to the natural fluctuations in our weight – with one study finding weight can change by an average of 1kg (2.2lb) in one day due to activity levels, fluid retention and diet.

But when it comes to Christmas time, body weight tends to fluctuate a lot. Research shows that at Christmas, people see their weight increase by 1.35% on average (about 1.2kg or 3lb).

Research from Australia also shows that adults gain about 0.65% of their body weight during the Christmas period (which falls in the middle of summer). This is particularly interesting, as the study found that participants tended to weigh 0.23% less in summer compared to winter.

This suggests that Christmas weight gain may be due to overeating alone – not because people exercise less during the cold winter months.

But is this weight gain due to increased body fat? Or is it due to constipation, fluid retention and extra food in our stomachs?

Calorie count

When you look at how much people eat on Christmas Day itself, there is little in the way of rigorous research.

But when we look at America’s Thanksgiving — a holiday that is synonymous with overindulgence and overeating — studies show that people eat about 3,960 calories at the Thanksgiving meal alone. This translates into a weight gain of about 0.5kg (1.1lb) by the end of Thanksgiving.

That’s about twice the recommended daily calorie requirements for the average adult woman and about one and a half times the recommended requirements for an adult man.

But just because it doubles the number of calories we need, this doesn’t mean we might gain weight.

For years, it was believed that eating an extra 3,500 calories or more over a week would result in a 0.5kg (1lb) weight gain. But research now suggests that this may not be true for everyone. Many factors can affect how easily a person gains weight – and how many extra calories per week are needed to do this.

For example, it seems that, in general, men gain weight more easily than women, which is linked to differences in body composition and where fat tends to be stored. Other factors – including body size and weight as well as muscle mass, age and physical activity – can also affect how easily you can gain weight.

Additionally, your genetics and other health conditions (such as an underactive thyroid) can influence how easily you gain weight.

So it is possible that even if different people eat the same amount of extra calories at Christmas, one person may gain more weight than another.

Another consideration is that many of us eat more calories than just one day during the holidays. For some of us, holiday indulgence begins in early December, or late November. This increases the chances that you will gain weight during the holidays.

But let’s say you’ll only be indulging at Christmas. It is not possible that you can eat a lot in one day which can lead to gaining a lot of weight. This is partly due to the way our body works – which can balance itself over a few days.

However, you may feel that one day of overeating a few days later as a result – meaning you feel “too heavy”, even if you haven’t lost weight. Also, if you gain a little weight, when you go back to your normal routine your body weight will return to normal.

Even if you gain weight over Christmas, research shows that this weight can be lost after the holidays and your lifestyle is stable.

But if you want to pay attention to what you eat during the holidays, as a nutritionist I can suggest the following things.

1. Be careful. Enjoying the holidays shouldn’t be about how much you eat – it can be about being on time and enjoying the holidays and eating mindfully. But if you do indulge, try to pay attention to how much you put on your plate – you can just eat junk food without thinking.
2. Eat more vegetables, salads and fruits. Save the calorie-rich snacks as a highlight – rather than the main event of the meal.
3. Try to exercise less. A Christmas or Boxing day trip with family and friends can help cut some calories and can also help with digestion and constipation.

If you still feel like you may have overindulged over Christmas, I wouldn’t recommend rushing into New Year’s resolutions. Instead, I would encourage people to make small changes to their diet and physical activity levels, which are easy to stick to.