So are you doing nutrisystem fully? Does the plan have any sort of addition for when you're working out hard? I'm doing Weight Watchers while also training for the TOT (and the Half in January), and I *have to* eat my "activity points". That's extra food based on the activity I do. It still works out to a net deficit in calories, BUT adds about half of what I burned back in. If I don't do that, I can't work out. I get weak and the workouts are just bad, even on the elliptical, let alone while walking briskly or doing my slow jog. (and I might have to start eating more soon as my runs gets longer b/c for me even my slow jog burns a LOT of calories) So Nutrisystem has such a plan in place? If so, please consider using that if you aren't. If not, consider eating a bit more food. It might help. It's hard enough to train like this, let alone if you really aren't taking in enough calories to fuel the workouts. Good to know, thank you for the specific recommendation! I used to have a bottle like that, and I lost it. I think it fell out of a bag at an airport or something. Maybe I'll buy another, see how that goes. If it still doesn't work, good to know that others will be wearing packs and belts and such!