Race is a quite simple casual running game, along the way, you'll be met by various obstacles: various food and fitness gear. You can collect the junk food to gain weight or eat healthy food or take exercise to lose it. As the levels progress, it becomes more of a tactical choice.
If you are too fat, then you may not be suitable for walking on fragile glass. If you are too skinny, then you may not have a chance to knock down more bowling balls in the end. What you have to do is learn to find a balance between the two.
For example, sometimes you need to avoid those tasty but BAD hamburgers,feed on vegetables and get through the obstacles.