I eat bananas that are only just ripe before a longer run, or an almost over ripe one after a run (or any time I need an energy boost). The underripe ones are slower burn, ripening breaks down the carbs into sugars.
It's really great for weaning babies too, especially mashed in with an avocado and a large spoonful of natural greek yoghurt, stuffed full of nutrients. (HEALTH WARNING: this recipe is totally lush, but not so good for the waistline)!