A small piece of advice I would offer to anyone who is thinking of spending a couple of hours a day writing: start chewing gum while you write.
I am not a gum chewer, and I think it should not be done in public, ever. Except possibly on planes to stop your ears popping. However, I found out the calorific way that when I write, my mouth likes the distraction of chewing.
I started bribing myself to sit down and write by saying I could eat chocolate while I did it. Now, I'm a suck on it until it melts kind of chocolate eater, so I was shocked to find that while I was writing, I would just keep popping it into my mouth and crunching down. When you are writing for a few hours straight, the amount of chocolate you can go through like that is just plain scary.
I have since switched to sugarfree chewing gum (along with giving up chocolate and caffeine completely). The chewing does seem to help my writing thought process, and also it stops me from eating anything else.
Seems like a small piece of advice, but saves me hundreds of calories a day, which would result in possibly an extra two kilos a month, making me 24kgs heavier each year that I write. So, after five years of working on this challenge, I would be three times my current weight. Chew Gum.