Most of us have probably wanted to lose some weight at some point or another, only to find out it's much easier said than done. And even if we actually managed to hit our goal, maintaining this new weight became all but impossible.

Why is it so hard?

It turns out that when trying to lose weight we aren't just fighting our daily temptations - we are taking on prehistoric mechanisms put there by evolution to ensure our survival. Couple that with our disastrous food environment, the growing obesity epidemic and fast lifestyles, and you've got a disaster on your hands.

So how can we get out of this vicious loop? To find out, I turn to dr. Stephan Guyenet - a neuroscientist, obesity researcher and author of the bestselling book, "The Hungry Brain: Outsmarting the Instincts That Make Us Overeat."