If you continually diet you are putting your body in a quasi-famine situation. It slows your metabolism down and breaks the thermostat. Diets don't work. They don't help you understand why you're eating more than your body wanted in the first place.
I myself believe that there will one day be time travel because when we find that something isn't forbidden by the over-arching laws of physics we usually eventually find a technological way of doing it.