So, you're a runner, right? Well, go take a Zumba class! Or you're a swimmer? How about some spinning?!
Your body can settle into a groove if you do the same workout all the time... keep things interesting and you'll shock your body - and that shock will being about a change!
The same idea of shaking things up applies to your calorie intake. Try fluctuating your calories a little bit some days... or maybe up your protein... or up your carbs... go vegetarian for a few days... keep your body guessing, and you'll reap the benefits for sure!