A recent study showed that greedy Starbucks eaters shaped up when faced with the calories they were consuming—but during the holidays, all bets were off. Around Thanksgiving and Christmas New Yorkers ate largely and indiscriminately at Starbucks, according to the very same study, the Times reports. Turns out, holiday gluttony is an annual event as predictable as the tree at Rockefeller Center and the Macy’s Thanksgiving Day Parade. But what drives self-destructive Christmas binge eating?

“One interpretation is that it’s the holidays, so you cut yourself some slack and you don’t really worry about it,” said Alan Sorensen, a professor who co-authored the study. Dr. Marina Kurian, medical director of the New York University program for surgical weight loss added her two cents: “We think, maybe wrongly, that we’re going to lose that weight gain by dieting in the new year.” At Starbucks the proof was in the Cranberry Bliss Bar: though customers did reduce their calorie intake after counts were introduced in April 2009, they reduced them even more in January, once they had time to reflect on what the hell happened back there in December.

And don’t think food purveyors are blind to the trend. Starbucks serves frothy, fatty holiday lattes and sinful desserts in December, only to introduce 90-calorie beverages come January. “Customers are thinking about getting the new year off to a good start,” explained Sanja Gould, a spokeswoman for the chain, which is smart enough to sell both the cause of and solution to America's obesity problems.