I'm sure eating this way had nothing to do with it, as I found my moods are both smoother and better since I've started low carbing. And what good will come from dumping a bunch of sugar and starch into your body?
Stick with it. My sympathies for your loss. This is a terrible blow and if you don't feel up to a "normal" level of activity, accept that you can't do it, and then don't.