Low carbon food is a struggle to get hold of in a lot of places. Fine if you've time to stop off at a grocery store or cook, but on planes, trains etc., most things are bread based, pasta based, or sugary cakes.
Pop into say Boots for a meal deal at an airport and you're pretty much limited to a tub of berries, Babybels, and those bags of processed meat.

Been on LNER a few times recently and food options were bacon rolls, cheese sandwiches, crisps and cakes. Bar the cheese and bacon, you end up wasting 90% of the offerings if you're avoiding carbs.