I think it's natural to feel a pull to fast after a feast, and feast after a fast. In addtion to the primal instinct of facing times of plenty and scarcity as natural, we've also had centuries of feasting before fasting within the religions of the world.
In the Catholic Faith, which is my home, we have fasting seasons of lent and advent, which are proceeded by Mardi Gras and Thanksgiving, and followed by feasting at Easter and Christmas.
These are times to voluntarily go without all the richness and comforts we enjoy every day. There are SOOO many spiritual benefits to fasting - when we aren't so self sufficiently meeting every comfort we allow God to bless us to show us how much He wants to do in us and for us, to transform us in our emptiness. Because let's face it, when we are full we don't want more. When we are comfortable we don't seek, Every person is inclined to pray more when they are suffering and life is hard than when they have it all picture perfect. Any ways....
A dear friend of mine is expecting her 1st baby... a week ago. She has been uncomfortable for a long time now. I decided that I would fast until baby is in her arms. Fast - meaning go without, deny my wants, as a sacrifice, the grace of which can be applied to her. We are united, and in a way 'bear one another's burdens'.
Having gained 3 lbs and 5 in over the last few weeks, skipping snacks and laying off the paleo treats (raisins, dates, paleofied baked goods) will do me no harm.
In fact, there are actually physical benefits to fasting. Intermittent fasting shakes up and wakes up our bodies a little bit. Check out the primal view: http://www.marksdailyapple.com/fasting/