Amazingly some people just don’t like eating food that much. They never have to struggle with calorie counting or self restraint. With this remarkable ability they ought to join religious orders where fasting is part of the trade, except many with this ability aren’t interested in religion.
It could also be that some of them are small town folk who have never had good cooking, complex dishes, fresh ingredients, fragrant spices.
There are a couple methods to induce appetite and perhaps turn people like you on to a love of food: cannabis, alcohol, sex, heavy weight lifting, watching disappointing team sports games, striking out after a night out, moving to a much colder climate. You don’t have to do these long term as they can, long term, distract from training for distance. Just as the initial catalyst.
If that still doesn’t work for you, this may be in born and you might want to see a Sports Nutritionist. Or you might have worms.