It's not easy to start over. I'm 13 years older, had to take a couple years off with heart issues, back at it again. It is said that it takes 7 years of training for a rider to achieve max possible aerobic ability. There' s a little "however" in there though. Past our mid-60s, we start to decay a bit even training as hard as we can. Every year is worse. So you'll be battling that at the same time as you're trying to improve. What'll happen is that every year you ride, you'll improve your fitness w/r to those who don't ride. And that's a big deal! The gap between you and your age population will increase.

What worked for me at your age was decreasing portion sizes. The fact is that as we age we simply cannot burn calories at the same rate we used to, no matter how hard we train. So we have to eat less. I now eat less than half what I ate 20 years ago and I still have more belly fat than I'd like to. As we age, for some reason our bodies want to deposit belly fat. Bummer.

A very important part of getting it back is going to the gym twice a week for 60-90 minutes each, doing full body workouts, say 3 sets of 12 reps, the last set to exhaustion. One day I do pulling exercises, the other pushing. The deal is that muscle burns fat and muscle loss is a serious problem as we age. Sarcopenia. So our #1 priority is to increase muscle mass. To get those muscles to burn fat, we get on the bike and ride. You'll want some sort of bike computer so you can see how much you ride. Try to increase your weekly mileage by about 5%/week until you get to 100 miles. This combo will drive your BP down, absolutely. Get a BP device. I use an Omron, take it twice a day. That way you can get mental rewards for keeping at it. My BP is always crazy high at the doctor's office, mostly because I enjoy talking to the lovely doctor's assistants who take my BP. My BP at home is real. At some point, you'll be able to get off the BP meds.