Even if you can't really exercise a lot just increasing non-exercise thermogenesis by standing, walking around house or , if a drummer fidgeting, you burn a lot of calories doing that. I think now they have designer drugs to increase NEAT as well a programs for obese people since obese people have lower NEAT.
Before I quit working I got real interested in the relatively new field of metabologenomics and gut flora in health and disease. it's amazing the connection with gut and inflammation and disease and even cognitive ideology and what not. Without bacteria ,and viruses ironically ,there wouldn't likely be any complex life on earth-since plants, fungi and animals dependent on them both. No viruses too many bacteria and no other life-no bacteria no plants, animals or fungi. Phytoplankton produce majority of oxygen in atmosphere. The smallest things can really make a difference. One of the reasons I pursued cell biology is my amazement when first looking in a microscope-you mean all those individual cells somehow come together to produce "life/me"? I've never really gotten over that from my first introductory biology course-which at the time I was a business major.
This is a 15 minute low impact exercise routine for seniors. Mostly stretching and bending - it will improve your flexibility and ability to reach down and lift things. Highly recommended.