It’s that comfortable time of the year, swimsuit season but a memory and holiday feast season about to begin. Widening waistlines are about the last thing on our minds—until the two to three kilograms gained over the winter sparks a New Year’s resolution.

Understanding why we tend to pack on a few pounds in the cold months and using a few of the following tips may give you a leg up on keeping your weight down this winter.

Calories In = Calories Out = Stable Weight

Generally speaking, here’s the formula: 1,000 calories ingested as food minus 1,000 calories expended in exercise equals stable weight. But winter mucks with that equation. When it’s cold outside we tend to eat more and move less.

One reason is that the level of serotonin, dubbed the ‘happiness hormone,’ diminishes in tune with the waning sunlight, leaving many of us feeling blue and some of us with seasonal affective disorder, a serious medical condition that robs life of joy. Either can sidetrack exercise regimens. Paradoxically, exercise increases serotonin levels, McGill University’s Dr. Simon Young said in a scholarly article in the Journal of Psychiatry and Neuroscience. However, when it’s sub-zero and pitch black outside, many of us opt for the sofa rather than the running shoes.

Less Exercise = Weight Gain

A 2011 study of U.S. arthritis patients revealed they are sedentary three more hours a day in the dark and cold months. Yet exercise improves joint function, reduces pain and can delay development of disability. “Even modest reductions in activity can have serious health consequences for people with arthritis,” said Joe Feinglass, of the Feinberg School of Medicine in Chicago. The Canadian Physical Activity Guidelines recommends a minimum of 150 minutes of weekly exercise for adults, varied in intensity according to age. That’s just over 20 minutes a day. More is better, of course.

More Calories In = Weight Gain

Serotonin also has a role in regulating appetite, so having less of it leaves us open to the raving munchies and in danger of snacking ourselves into a larger pants size. The Dietitians of Canada website www.dietitians.ca suggests watching portion size, snacking only when hungry, eating slowly and choosing wisely.

Alas, researchers are finding that if you have already packed on a few extra pounds, it’s easier to gain more in winter. Body fat is a good insulator, so obese people cool down slower and their bodies react more slowly to the cold, Simon Fraser University researchers Dr. Matthew White and Andrew McMillan have found. “This means cold weather can predispose already overweight and obese individuals to more weight gain,” White said.

Less Exposure To Cold = Weight Gain

Our ability to come in from the cold also contributes to weight gain. The human body has evolved a means to warm up quickly—brown adipose tissue (brown fat). Brown fat is different from the white fat that accumulates around our midriff. Stimulated by exposure to cold, the body burns brown fat, which can produce 300 times more heat than other energy stores. More stored calories are used up when brown fat is used to heat us up.

But brown fat diminishes as we age, and the body is stimulated to use it a lot less often in modern adults, who not only live with central heating, but set their thermostats higher than previous generations. And recently a link has been made between spending more time in the warmth and loss of brown fat.

There’s also a link between the time you spend in bed and the size of your waist. People who get less than five hours of sleep are twice as likely to be obese as those who sleep seven to nine hours, according to research at Columbia University.

Core body temperature drops as the most restful sleep phase begins, but if you’re hunkered under heaps of blankets, your body can’t offload that heat. A chilly bedroom is best for rest, but the dining room should be toasty. A study at Maastricht University in the Netherlands revealed that women who dined in a room at 22 degrees Celsius rated themselves 20 per cent hungrier and ate 10 per cent more than women who dined at a cozy 26 degrees.

So what strategies can you use in the battle of the bulge?

Keep your bedroom temperature between 16 and 20 degrees Celsius.

Avoid visiting Mr. Muffin or Dudley Doughnut when you’re blue or stressed out. www.dietitians.ca has a list of healthy snacks that include fibre, which keeps you feeling full longer, and protein, which delays digestion of carbohydrates, giving you more energy for a longer time.
Party-proof your appetite. Instead of skipping a meal so you can eat more at a feast, try having a snack before you go so you won’t overeat.

Measure meal and snack portions and avoid mindless eating. Tips for keeping meals in proportion can be found at www.diabetescareguide.com, including using smaller plates and removing snacks from the package and serving them on a plate, instead of eating them right out of the package.