Every December, the same New Year Resolution: We - the (flabby) people of the world - decide that we will start going to the gym on January. For real. It's not only a popular culture factoid. Here's the Google data that proves it.
As you can see, the search volume for "gym" skyrockets at the end of every single year. There's a small peak approaching winter, but the huge spike is always at the end of December.
And seriously, this year I'm going to the gym or hell be damned. It's that or I'd die of arteries clogged with pork and my kidneys collapsing, overflowed with uric acid and wine because of my ongoing Spanish dinners overdose.