The simple message from the book is to do vigorous exercise daily or at least three times a week. Throughout the book is the science and stories about how exercise can improve the quality of life whether you're stressed or suffering from a disease. I think most people can relate to many of the topics in the book because they may be going through it or know someone who is, such as obesity, Alzheimer's, addiction, depression, and ADD. Even for topics that I didn't find to be relevant in my life, I found the scientific evidence fascinating. Whereas medication almost always have side effects, exercising isn't harmful. As long as people can keep slowly work up to a vigorous pace and do it consistently, they'll see that exercising is good medicine.
cold have been shorter only because the author makes the same point more than once. but they are good points. it is well established that regular exercise can improve mood. but this book trys to get into how this process happens. the author does seem to have a bias toward walking and running as the prefered forms of exercise for health. but just understanding how anything done for physical health affects mental health is a great place to start.