Sometimes Derrick questions the usefulness of our two cats. (Granted, they don't do much but eat and sleep, but I do like when they plop their warm furry selves on me for scratches and a nap.)
Anyway, yesterday I had my first run with a backpack and I was looking around for something to weigh it down with, when I spotted the perfect thing - a bag of cat food. It was 8 lbs, the perfect starting weight. It made a nice rattle as I ran through the snow, and hey, it's always good to carry snacks.