On most English trails I doubt you would go for more than a couple of days without finding a pub or shop to buy food from. On the JMT there will be nothing for 110 miles between the Muir Trail Ranch and Mount Whitney.
This means I have to actually think about the food in detail. It needs to have enough calories to keep me going and be light enough to actually carry. There are different approaches, from carrying numerous energy and chocolate bars (and that’s it) to carrying the kitchen sink. Neither of those ideas appeals to me.