I have had the exact opposite experience. Prior to 2012 I was in college and was overweight/out of shape and always felt like crap. I decided to get into shape:

I have had the exact opposite experience. Prior to 2012 I was in college and was overweight/out of shape and always felt like crap. I decided to get into shape: did intense cardio and HIIT workouts, lifted weights, and got into excellent shape within a year. I lost 50 lbs, went from being able to do 0 pull ups to over 20, I ran a few Tough Mudders (12 mile obstacle course races), etc. I still run, lift weights, and keep my body fat % low, and if I can help it, I'll never go back. If I go days without exercise I start to feel terrible, foggy headed, lethargic. One 5 mile run will immediately make me feel great for the rest of the day.