Why do people put on weight in winter?
Holiday weight gain is the most obvious reason for putting on a few pounds in winter. “Most people tend to eat and drink more during winter time, especially around festivals such as Thanksgiving, Christmas, Hanukkah, Las Posadas and Kwanzaa,” says Dr Ann Nainan, family doctor and Healthily expert.
The colder weather can make exercising outdoors harder, too, so you’re burning fewer calories. But it also seems that human bodies are set up to make weight gain in winter easier, and weight loss in winter more difficult.
So here are the facts you need if you’ve ever wondered: is it normal to gain weight in the winter?
1. Body fat maintenance
“It seems that eating hearty, calorific foods may be what your body is supposed to do at this time of year,” says Dr Ann.
Think of it this way: for your ancestors, being overweight could have been less of a threat to survival than being underweight – and the latter was much more likely to happen in winter, when there was less food to go around.
And it might be that our bodies haven’t evolved to work differently, even now that food is readily available year-round. This may mean that as you go into winter, your body is programmed to maintain a certain level of body fat. Which may be where the familiar urge to eat more energy-dense foods and store more calories comes from.
2. Lack of sunlight
Ever wondered why it’s often easier to keep weight off during summer? While more research is needed, 1 study found that some of your body’s fat cells – which lie just beneath your skin – shrink when they’re exposed to blue light from the sun.
This means your cells don’t store as much fat in the summer. So when we don’t get enough sun during the darker, shorter days, fat cells don’t shrink, and may cause weight gain, as they can store more.
However, the researchers stressed that this was a very early observation, and don’t recommend trying to lose weight by sitting in the sun, which has its own health risks (read more about sun safety.)
3. Programmed for winter weight gain
Do you blame your lack of willpower for overindulging in the winter? One study might help you let that pressure go.
The results may help explain why it can feel so difficult to resist the urge to overeat, especially during the winter holidays:
- scientists used computer modeling to predict how much fat animals (including humans) should store in their bodies
- they found that having a higher weight than the ideal level only had a small negative effect on an animal’s energy levels
- because of this, it’s thought an animal has no – or very weak – controls to stop itself gaining weight, especially when tempted with a plate of delicious food