I have no idea about calories and suchlike, but if you're hungry - eat! You're asking your body to put out more energy and it needs fuel to do this. As long as you eat healthily, not too large portions, often - and most important, don't go into a bike ride hungry, I think your natural appetite control will take care of it just fine

If I'm not eating enough I notice that I have trouble sleeping soundly, or wake up starving.