I completely agree with this. Anecdotally from my own experiences. About a year ago, I decided it was time to be in shape again, lose some pounds, feel better, all that. So I went to the gym regularly, went for runs, bike rides etc, went dancing on the weekends. Nothing super heavy, just a lot of solid activity. About 2 months ago, I sort of fell off the wagon because I let work get in the way (then laziness crept in a bit too). So I am currently well versed in the whole gamut of exercise benefits (and non-exercise drawbacks). They directly relate to programming too! Not exercising is correlated with:

- Not sleeping well

- Feeling anxious more frequently

- Lack of focus

- Lack of motivation

- More difficulty following complex problem/solutions

- General irritability

After this next deadline in a week, I'm renewing my commitment to exercise and putting it in the non-negotiable list of things to do everyday.