Ride a bicycle a few times/week for cardio and leg buildup. That will help with all the required standing, and tall seat foam help the transition.
What works for some may not work for others, but in general:
Get into a habit of eating wholesome foods. You'd be surprised the larger health food stores carry normal people food too, not just tofu (yuck!) and grass. It is more expensive and work to prepare your own meals but you can slow the aging process, and be more fit than those in your age group.
Avoid adult beverages, coffee and teas.
Lots of water is needed, before and during events.
Yes, potatoes are carbs but are simple (no, not complex as we are led to believe) due to their fine cosistency, and are a new-world food - not the best for you, even though they are cosidered a tuber and/or vegetable by many. I keep my intake of them, tomato, and peppers to a minimum for those reasons and due to their solanine content.
It is preferrable to use coarser whole grains (old-world oat groats, wheat berries, or minimally-processed grains) as they are on the complex side and will deliver longer-lasting, healtier results than potatoes. If you do pasta then seek out whole grain or whole wheat products.
Save the fats (dairy, meat) for after the event to rebuild muscle. The body has cravings for it and needs the stuff then.
Bananas contain higher levels of potassium than most fruits so certainly use them but dried figs have a superior level of that mineral. And I don't mean fig bars as they are loaded with processed cane sugar which will take you way up then way down. Trader Joe's - if you have them in your state - sells plain (sun) dried figs and bananas. Throw 1/2 a bag in your fanny pack to munch on at the resets.