Are you recovering properly from your workout?
Don't forget that the recovery period post training should last as long as the workout itself.
If you've been on the bike for four hours and immediately have your recovery drink when you finish, you're on the right track, but don't stop there. Make sure you re-hydrate as well, and gradually, over the next four hours, keep the calories coming in with a gradual shift from the higher glycemic foods (the first being your recovery drink), then perhaps some raisins (which are one of the most alkaline foods you can possibly eat; important in helping the body to return to its ideal pH after likely becoming acidic during training) or yams for example, toward the normal eating we engage in during the day away from training- higher percentage of protein & fat as our bodies recover.
Recovering properly is of utmost importance as it will not only help your body reap the benefits of the session you've just completed, but will also prepare you for the next workout to come, whether it's later the same day or tomorrow.
Refer to the detailed, easy to follow guide in The Paleo Diet For Athletes if you need more detailed information.