One of the biggest problems of modern life is that we evolved a taste for fattening foods but did NOT evolve much of a taste for healthy exercise.  Why?

"There was never any evolutionary selection pressure to make us like exercise. If you are a Neanderthal or Homo erectus or an early modern human, you didn't think, "Gee, I'm going to go for a run so that I'm not going to get depressed." They had to go long distances every day in order to survive. Not exercising was never an option, so there was never any selection pressure to make people like exercise. On the contrary, there was probably selection to help people avoid needless exercise when they could."

I might disagree with you but I don't feel like gettin up right now....

I didn't fight my way to the top of the evolutionary pyramid just to spend an hour a day on a treadmill!

Seriously though, the circuitry between "I'm running" and "I'm not going to get depressed" -- WHO THOUGHT OF THAT???