Everyone is different (you will hear that a lot!) but there are several things that were common to most of us. Start eating now! Stuff you both love. If he puts on a few pounds that's great news too.

I was very fit as well and it benefit me greatly. I tried to work all the way through and ended up missing two consecutive weeks at the end. I know some that didn't miss a day and others who could not work from the midway point on. Chemo days are long and I never went to work after. I had Cisplatin and very few side effects but the rule of thumb is day 3 after Chem is the worst: mild flu like symptoms. I did chemo Friday in case I needed to lay in bed sunday and be ready for work Monday.

Your desire to work will help keep you both in the fight and IMO is a very good thing. Just remember to cut yourselves some slack if you need a day here or a day there to rest up in the midst of treatment.