I think you're confusing 'carbs' with 'grains' (as the title to your post might suggest); humans are quite able to process carbs quite easily. Every eat fruti? How about vegetables? Yeah, those are carbs. But they do take a while to break down, plus they contain fiber, which is also good for you body. Grains, on the other hand, are BAD carbs (I'm talking about processed grains here, not the stuff you'd pick off a wheat plant growing in a field; good luck trying to eat THAT.) They break down too quickly into sugar, which is quickly absorbed into the blood stream, thus causing high spikes in insulin which leads, eventually, to insulin resistance. Stay away from most grains, eat lots of fruit/vegetables and lean protein and add in some poly unsaturated fat (almonds, cashews, avocado, olive oil/olives) and you'll be on your way to a leaner, healthier you.