I don't think it's a response to exercise because it happens when I'm not, such as now. What's really weird is I also get tired after moderate-to-large meals as well. I hope that helps rather than confuses Like today... for lunch I had a peanut butter sandwich, two high-carb drinks, and half a chinese chicken salad, and about 1 hour afterwards I could barely stay awake for the life of me. I couldn't think either. It's like I shut down. Now, 3 hours post-meal, I'm much better despite not eating anything.