I've no expectation of undoing 25 years of inactivity in a season, but as I'm starting out from such a bad position there's low hanging fruit to be found. After about a month, it seems as if my sleep cycle has improved, not so nappy feeling during the day and sleeping more through the night. If I keep this up, the docs think I may be able to get off of the blood pressure meds. Leg strength has noticeably increased when I'm stopped with my motorcycle at a light. And my pants seem to be growing in size instead of shrinking.
The end result should be that I'll be in good shape for my next motorcycle trip, and I want to earn a few more certificates along the way!
But I bet that the really dedicated IBA'ers have a lot of tips to share.
Five years ago it became apparent that my age and inactivity was having a negative affect. I changed the rear bearings on a vehicle and was sore for a week. After that, I decided to start lifting in the gym to gain strength and prevent muscle loss. Like you, I didn't have any desire to compete as a power lifter or a body builder.
I started lifting, and only lifting. I didn't make any changes to diet, activities, etc. Once I started getting stronger and a few pounds dropped off, I bought a fitbit and started walking an hour a day on my lunch break. When I was young my father would walk ten miles every day. I thought he was off. Now I understand.
Once I'd established that habit I started looking at my diet. The first thing I learned was that you shouldn't think in terms of diet. Diets are temporary and negative. I don't get to have this; I don't get to have that. I started thinking in terms of nutrition, which is permanent and positive. I get to have this; I get to have that. I dropped the junk (mostly) and focused on protein, fat, and complex carbs. I increased my water intake to around a gallon a day, depending on activity levels, heat, etc. I don't drink my calories; milk, juices, sodas, coffee. (I never liked coffee anyway so that wasn't an issue.) Now I do what is referred to as time restricted eating. I only consume calories in a 9-10 hour window. That gives my metabolism rest for 14-15 hours a day.
I've learned a few things in the past five years; some by accident, others not.
1. Make one change at a time. If you try to change to much at once it's overwhelming. If make one change its easier to manage and you'll have a sense of accomplishment. It also makes it seem possible.
2. Weight loss is through nutrition. Strength is through weight training. Endurance is through conditioning (cardio, etc.)
3. Fitness isn't a goal; its a way of living.
4. Train for life, not just for a specific thing. I'm able and ready for daily living and everything that comes with it. Including IBA rides.
5. Training/fitness improves sleep, as you've already discovered. It will also improve your mental state of mind. I live in the north and used to have issues with seasonal depression. The only thing that works to prevent it is training.
I hope this helps.