I eat hearty for breakfast and dinner. I don't eat lunch as such; I just snack throughout the day. Dried fruit and nuts are standbys for me. Nuts are a relatively concentrated calorie source containing heart-healthy fats and protein. I usually divide a cereal bar into 2-3 parts and eat a section at a time. Ditto for a piece of cheese (sharp cheddar). For long trips I bite the bullet on $$ and snack on freeze-dried fruit, which is a lot lighter than dehydrated fruit.