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Shedding winter weight: Is biology or human habit to blame for seasonal gain?

With bathing suit season right around the corner, many are desperate to lose the excess weight they've put on during the dark, dreary days of winter.

But, do we have ourselves to blame for overindulging, or is there a biological explanation for why we pack on the pounds during the colder months of the year?

More likely than not, a combination of factors are to blame, Rebecca Blake, senior director of clinical nutrition at Mt. Sinai, said.

Winter ushers in the holiday season, first with Thanksgiving and then Christmas, holiday parties and New Year's.

"So, people tend to get in that festive mode and they over consume, whether it's alcohol, whether it's, you know, sweets, treats, other high calorie foods," Blake said.

While people are consuming more generally, they're also eating things that are heavier and less healthy, instead of lighter foods that are preferred during warmer months.

"We sort of hunker down and crave these comfort foods. Now whether or not this goes back to survival, I think you could probably make a case that it might in some ways," Blake said.

Stockpiling calories may have been necessary for our ancestors when food was less readily available and caloric intake was a matter of survival.

"We don't need to, like, wrestle a wooly mammoth down to the ground anymore to get enough calories in, right? Instead, it's like you're just ordering the fettuccine alfredo, the caesar salad, having, you know, three pieces of bread with it, and the chocolate mousse cake."

To make matters worse for our waistlines, the season's colder air and shorter period of daylight inspire fewer people to get outdoors - meaning fewer calories burned than during other seasons.

"So, there's a double whammy because we might be eating more calories, but we're burning fewer calories just because the weather is not as conducive to things like outdoor activity," Blake said.

While a typically active person might ride their bike to work in the springtime, he/she is more likely to drive during the winter.

Other psychological conditions, like seasonal affective disorder, can also come into play.

Studies show that winter's reduced sunlight and shorter days can lead to a depressed mood, which can cause people to turn to food for comfort, Blake said.

On average, weight gain during the wintertime ranges from 5-10 pounds.

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And while a culmination of factors makes it easy to gain weight, neither biology nor human habit make it easy to shed fat in the following months.

One theory is that a "thrifty gene" may be to blame.

"Back when we were hunters-gatherers, et cetera, we had to have a protective mechanism in place so that we didn't starve to death. So we evolved as beings that could store fat very, very effectively, and endure times of famine very effectively," Blake said.

However, there's not a similar mechanism that supports us in the opposite direction. The body will not compensate for lengthy periods of over feeding.

So, what's the best way to prevent seasonal weight gain?

Counteract it during the rest of the year, so that it's not a cumulative effect. At get-togethers, focus on your company and other social aspects, rather than food.

And finally, "don't wear your buffet pants to the party," Blake said.