This time of year, fitness instructors and personal trainers never tire of announcing:  “The average person gains 10 pounds during the holiday season. Work the gym into your holiday plans!”

This statistic—that the average American packs on 10 pounds between Thanksgiving and New Year’s—is the fitness equivalent of an urban legend. Something that we all believe even though we’ve never seen the data.

That’s because the data doesn’t exist. According to the New England Journal of Medicine, the average holiday weight gain is actually only about a pound.

The real problem is that most people don’t take off the weight come January—or ever. The study, which you can download here, concludes with this fact-based finding:

“The average holiday weight gain is less than commonly asserted. Since this gain is not reversed during the spring or summer months, the net 0.48-kg weight gain in the fall and winter probably contributes to the increase in body weight that frequently occurs during adulthood.”

The good news: Taking off one pound is less of a project than tackling ten. The bad: one measly pound can make a big difference in adults over time.