I had the same mindset as you before. I would run 5-6 miles per day and add in a 10-12 miler once a week. Then I would hit the gym and lift weights 4-5 days a week. I was so tired all the time and was eating a lot of CW foods. At work I would just feel terrible and tired all the time. But since I found Paleo I stopped chronic cardio and started walking instead of it. I sprint and play basketball twice a week. My sprint protocol is 4x400, 4x200, and 4x100. On my last few sets of 100s there is pretty much nothing left in the tank. Those last few sets are definitely not fun lol but they doing it is extremely productive in my opinion. My 5k times have been getting progressively faster the more sprinting I do and the less jogging I do. And with sprinting your whole body gets pretty ripped.
"If man made it, don't eat it" - Jack Lallane
People say I am on a "crazy" diet. What is so crazy about eating veggies, fruits, seafood and organ meats? Just because I don't eat whole wheat and processed food doesn't make my diet "crazy". Maybe everyone else with a SAD are the "crazy" ones for putting that junk in their system.