I used to have plenty of energy running 40-50miles per week, but when I ramped up to 80mpw I started nodding off in my chair by 1 PM. Then despite the higher mileage and more intense training, my race times slipped. My half went from 1:23 to 1:28, and I felt drained, irritable and angry unless I took a long break. After digging in, I learned that very high mileage can deplete iron levels. Once I focused on improving my iron absorption, I finally got my energy back and everything clicked. Even while holding 80+ mpw for the upcoming SF Marathon, I still knocked 5% off my Bay to Breakers time (48:51 this year) and cut my 5K PR from 19:17 to 18:37.