The plump Santa Claus whom children all over the world will be keeping an eye out for on Christmas Eve is actually a pretty modern creation. The jovial version of St. Nick popular in the U.S. wasn't always so soft and cuddly — in fact, in Europe, Santa is depicted as a much thinner gift-giver who sometimes bucks his reindeer-powered sleigh to travel by foot. Here's what we know about Santa's expanding waistline over the centuries:

Santa wasn't always fat?
Nope. The modern version of Santa Claus is loosely based on St. Nicholas, the patron saint of children who was born around the year 270. He started life out as a monk and went on to become the Bishop of Myra (a town in what is now Turkey), giving his inherited fortune away to children by throwing coins and gifts through their windows. While the signature white beard has long been part of the uniform, early depictions of St. Nick show him to be, well, svelte.  

When did he get fat? 
Fairly recently — and Coca-Cola is at least partly to blame. St. Nick's signature red suit, in particular, became a recognizable part of the wardrobe sometime in 1931, when artist Haddon Sundblom illustrated Santa as a jovial, rosy-cheeked Coke-drinker for a widely circulated magazine ad. The soda giant was trying to convince consumers that Coca-Cola wasn't just a warm weather thing. Sundblom was likely inspired by the work of cartoonist Thomas Nast, who in the 1890s depicted Santa with a big warm belly. Nearly a century before that, early American writer Washington Irving (The Legend of Sleepy Hollow, Rip Van Winkle) was one of the first to balloon Santa's waistline: In an 1809 book, he switched skinny St. Nicholas and his episcopal robes for a fat elf in traditional Dutch garb. And yes, he looked terrifying

Okay... but why is he fat?
Santa's round, soft features are all part of the charm. Think of it this way: Would you rather have a jolly old soul selling you sugary snacks and drinks, or a skinny pious guy with a walking stick? Another theory: His belt-busting gut could simply be from all those snacks left out by children on Christmas Eve. One infographic playfully calculates that thanks to the hundreds of millions of kids who leave out cookies and milk, Santa consumes close to 38 billion calories every Christmas Eve.

Is it time for Santa to slim down?
A few critics think it's time America's Santa lost some weight, and that he no longer promote "a message that obesity is synonymous with cheerfulness and joviality." In the same vein, professional Santa Roy Pickler, 63, lost 88 pounds on The Biggest Loser and says that his newly ripped physique won't stop him from spreading Christmas cheer. "Santa is a role model," says Pickler, "and kids don't want to have a role model that's fat." Well, I beg to differ, registered dietician Beth Kitchin tells CNN. Like a lot of people, "I don't think Santa should be skinny." 

Sources: An Idea, CNNColour Lovers, Life's Little Mysteries, PLoS One, There is Really a Santa Claus