Do you know the feeling of being full to the brim after having a meal? Wanting to unbutton those trousers and let that belly bloat out? And do you remember the thought of regretting that you had eaten too much? Wishing you had at least avoided that extra helping or that second slice of cake? You have probably heard that the reason for our eating behaviour is related to humans' evolutionary tendency to store as much energy as possible. In a harsh environment, this made it easier to survive. But what happens when you take a species that has evolved in a harsh environment for millions of years and put it in an environment with unlimited resources? This is the experiment we have been conducting with the human species on a global scale for the past half century. Interestingly, all the survival strategies that saved us from extinction are now turning against us, making us fat and sick by the billions. Are we doomed to continue down this path of destruction for ourselves and the environment, or can we use our big brains to reverse it? I choose the latter. The key is to understand what is happening to us and why.