Spike has put on some weight after a slow week at the library, so much that Rarity refuses to take him gem hunting. Things go from bad to worse when Twilight puts him on a diet and he realizes how much he'll miss eating gems and his favorite fattening foods. The Cutie Mark Crusaders see this as an opportunity to earn their personal trainer cutie marks and put Spike on an exercise program in hopes that they'll get him back in shape.

EDIT: Popular Story on 2/15! Thanks, guys!