Do a search on intervals or other forms of higher intensity training to make the best use of your time.

And if you have a weight problem do NOT follow the advice to eat a snack. Do not add calories! You just lost 100 pounds and the weight will come back very very easily.

If you're having a problem with being overfull on your evening ride--eat HALF your dinner before the ride, then nuke the leftovers and eat them after the ride. That way--pre-ride energy boost and post-ride recovery snack with no additional calories. Very clever!