OK, you have tried to follow the oft recommended route of 30 minutes exercise/high activity a day, and failed. What else could you do to stay in shape?
Well, to be fair, I think there is no substitute for good exercise. Trust me, I have been on both sides of the table – a sloth earlier who thought just walking for 10 minutes every day was enormous exercise, and now, a bit more wise bloke who runs his 5 Kms at least twice a week. I can feel the difference that significant physical exertion can make.
So, yes, do try to spend at least 15 minutes every day in a good amount of physical exertion.
At the same time, the alternatives I suggest below could at least ensure you become reasonably healthy. These could be a lot easier than doing a 30 minute exercise every day, and if not, some of them could be at least more fun!
Some simple dancing ideas you can try
Salsa for health
Zumba for seniors (and the not-so-healthy youngsters too, I presume)
5-10 Minute Yoga
Have a Standing Desk at Work
An Easy Workout You Can do Even in Bed
Simple Stretches You Can Do Anywhere
5 Simple Stretch Exercises You Can Do Every Morning in Just 5 Minutes