Do we really put on weight over the winter months?
The middle of winter is here, and frustratingly, many people out there will be noticing the affect winter has on their middles.
Is there any reason for this, other than the typical hypothesis that we exercise less and eat more when it's cold and dark?
Research by the University of Exeter in the UK suggests we all have a "target weight" for survival, and that naturally fluctuates with seasonal requirements. In the study published earlier this year, the researchers claim that in terms of evolution, being slightly overweight has never really been that problematic. If you're underweight, however, you're at risk of dying of starvation if food becomes scarce.
The caveman's view
If we take a caveman's view of winter, that's entirely possible. However, as this research suggests, the biological strategy to counter the "risk of starvation" (ie the one that promotes weight gain) is still present today, even when famine is uncommon. Put simply, because our ancestors thousands of years ago used to gain weight to get through the cold weather, our 21st century bodies haven't figured out a way to get around that.
This study was completed using computer modelling, so more research is necessary to find out what exactly that "target weight" is, as the scientists involved couldn't speculate. Moreover, those involved in the study also struggled to explain why our biological behaviour has not changed since the prehistoric era.
According to other research, the amount of sunlight we get may also play a part in winter weight gain. Scientists from University of Central Lancashire believe that a lack of vitamin D reduces fat breakdown and allows for the body to increase its fat storage. The calories you consume in winter, it is thought, are more easily stored in this way instead of being used as energy.
Link to SAD
There's also an argument that general Seasonal Affective Disorder, known as SAD, plays a part in weight gain. Those who struggle with their mood when it's cold, dark, and depressing may get a hit of serotonin – one of the chemicals in your brain that promotes a feeling of happiness – when they eat particular foods.
Though the research around this area is vague, there is some suggestion that starchy foods – breads, pastas, and so on – can deliver this serotonin hit with the most force.
Getting sick in winter may also be a contributor to weight gain. A review of studies from the Medical Hypotheses journal found evidence to suggest that the bug named "adenovirus-36", which can cause upper-respiratory infections (usually known as "the common cold"), increases the size and number of glucose receptors on your fat cells. With bigger and more plentiful receptors, you're giving yourself a lot more space to fill with actual bodily fat.
It also pays to think about the effect of your immediate environment in winter – that is, the people you're around on a daily basis – and how they can affect your weight. New England Journal of Medicine research shows you are 57 per cent more likely to be overweight if you have overweight friends, and 37 per cent more likely if you have an overweight spouse. If others close to you are gaining weight, it's easily for you gain too because you'll often eat the same food and follow the same behaviours.
What you can do
With all that science said and done, we're not all doomed to get larger in winter. These are only increased statistical likelihoods of weight gain, not absolute certainties. And there's much in your power you can do to buck any cold-weather weight gain trends.
Keeping up with your summertime exercise regimen, or a cold-weather version of this, is a given. While it might be some time before anybody sees you in your togs, you don't have to use that as an excuse to limit your activity. Maintaining a regular workout schedule will mitigate some of the suggested weight gain likelihoods.
While you can't change a biological predisposition of gain weight to prevent starvation, to compensate, you can also help the situation by eating less. This is especially relevant if you're reasonably sedentary throughout winter, because you don't need to consume a lot of calories when you're not moving a lot.
Train your body to expect less food during winter, and you'll soon find it learns how to manage.
Written by Lee Suckling. First appeared on Stuff.co.nz.
Related links:
The trick to exercising everyday
Does cold weather actually cause the flu?