I used to work with a guy who would fast on Wednesdays for religious reasons. After a while, we realized that we shouldn't ask him any technical questions on t

I used to work with a guy who would fast on Wednesdays for religious reasons. After a while, we realized that we shouldn't ask him any technical questions on those days, as he simply couldn't answer, or didn't provide good answers. A few years later I went on a diet (lost almost 30 pounds, sadly since regained). I experienced the same effects - I was irritable, and didn't produce my best work. This was probably a contributing factor to my being selected for a layoff.