this is about 8 pints on a Saturday.
Christ. That's a lot of beer. Those calories are going to sit around not getting burned up, then turning to fat.
Little and often,with food. That way, your body uses the energy more efficiently, and stores less fat. Many people stare themselves for ages then eat huge meals, which is bad, because the body naturaly stores more fat in anticipation for the periods you're not eating. And if you used to eat badly, then your body wil still want to store more fat, as it's become conditioned to do so. The older you get, the slower it gets in breaking down fat, so it gets harder to do so. I eat less than I used to, but now put on fat much more easily, as my metabolism has slowed.
you're churning out a good milage, but to burn more fat, you'll need to rie faster. You mentioned somewhere having had heart issues, so this may be very difficult for you. Try to eat sensibly, keep up with the biking, and good luck.