The book says even moderate exercise is good for you, in many, many ways. However, vigorous exercise is good for losing weight. Moderate exercise can help you to keep the weight off in the first place. Aerobic exercise is good for you, anaerobic exercise is good for you, even weight training is good for you. It is surprising how much sports exercise science has come out recently. I am not sure I buy all of it.
One thing that disappointed me was that it did not tell me how I could fix my knee. It said the best thing was to ensure you don't get a knee problem in the first place - thanks a lot. OTOH, it said long term marathon runners had no worse knees than the rest of the population, and that even if you do have knee problems you are just as well keeping up what exercise you can. However, don't do cortisone or take anti-inflammatories as a matter of course.
There are many accounts of lab experiments on mice and rats. So much so, I was reminded of the bit in Hitchhiker's Guide to the Galaxy in which Slartifartbast describes to Arthur Dent the sublimely subtle experiments the mice have been running on people to guide their development.