Writers sit in front of their computer and type, type, type, at least they should, because writing requires sitting. But sitting for more than three straight hours can kill you.
It lowers your metabolism, making it more difficult to burn away calories. Writing without exercise leads to type 2 diabetes, cardiovascular problems and of course obesity. And consider eating while you write; cookies, or snacking on potato chips, drinking a coke, all of which, by the way, sounds like fun eating to me, but will turn your tummy to blubber while writing. Read what Dr. Hamilton has to say.
As I have stated before, I like to drink two to four cups of Oolong tea in the morning with a light breakfast before writing. But if it is a good day and the hours flow by being caught up in the chapter I am working on, hunger is appeased by a snack mix I put together. In a large plastic bowl I have chopped walnuts and sliced almonds along with raisins, pitted dates, and sometimes dried mango. Bottled waters is also on hand.
Naturally we writers get stuck from time to time, our brain needs a brief rest while we gather ourselves for another onslaught on the keyboard. When that happens I get out of my chair and do some stretching exercises. I do back bends, quad stretches, wrist stretch, neck bend, shoulder and triceps stretch.
It is much better to do a few exercises, even isometric ones, which I also do, than to go from your computer chair to your television seat where you sit for even more time. Perhaps even eating more of those wholesome foods like Twinkies, Ding Dongs, or a Forrest Gump box of chocolates.
I do find that when I eat my nut mixture with raisins and dates, drink tea and water; do some light exercises during writing breaks, and take a walk when writing is done for the day, that not only do I feel better, but I have more energy, and my mind is more focused, more creative. And the writing is better.