maybe you are just not eating enough. for an idea of how much you need to eat you could take your Basic metabolic rate and add calories burned during the ride. 35-45km depending all on how you ride could be another maybe 750-1250 calories. got a heart rate monitor? that could give you an estimate. are you losing weight?

i eat a lot of Eggs, raw cheese, raw milk. raw cashews, raw walnuts, peanut butter without oil or sugar added, beans, (brown) rice, whole wheat everything whenever possible (no white bread, white rice, white pasta, etc.). potatoes are not really good, high glycemic, like white bread, but they sure do taste good. i eat an apple everyday. Then, as many vegetables as possible. kale, chard, spinach, and salads. beets are real good, but i don't love them. quinoa is a good grain for vegetarians, supposedly it is a complete protein.

what are you taking in ON the bike and right after?