If you have a favorite activity (running, walking, cycling, Zumba, yoga, etc.), then there will be stuff you can buy that make the activity more enjoyable. Set yourself up an Amazon or other wishlist of fitness gear, clothing, and books, and on the comments list a goal, such as losing 10 pounds for a new technical shirt. When you meet that goal, buy your item!
It may be even better if you can get someone else to buy the items for you, as a bank.