The weight, that is. You're not the only one trying to lose holiday pounds before the New Year's party starts -- celebs like Matt Damon and David Spade are also working off that extra helping of mashed potatoes.
Matt hits the pavement in Miami, while David spins his pedals so fast they're a photographic blur at The Sports Club in L.A.

One thing (and probably the only thing) the two have in common: headphones.