4: Be restricted in your calories by having to carry everything on your back.
3000-4000 calories per trail day was typical during my 1,900 PCT miles. I never had to restrict intake due to weight concerns. Also binged on burgers and ice cream at every opportunity in town.
This is what one of my larger resupplies looked like, 31,750 calories for a 7-day stretch:
https://www.flickr.com/photos/cmartinpct/14501624495/in/phot...
I gained 5 pounds overall, but started in decent shape without much to lose (125 lbs).
Many thru hikers bend the rules for bear canister use. We carried canisters because we had to, but I don't know any PCT nobo'er who was able to cram all their food inside for the long Sierra Nevada (JMT) stretches. We slept next to our food so that we could chase away the bear.
6. Repeat.