Have you read this book: Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen?
I love that book. McDougall manages to populate the narrative with a whole cast of wacky, real-life ultrarunning characters. While doing so, he traces the roots of the human race as persistence hunters. Before we invented guns and spear-throwers and whatnot, we ran our prey down. We have the ability to keep up with and surpass (to the point of exhaustion) a horse, an antelope, any herd animal, over the long haul. The way we look, how we eat, how we breathe, why we think ahead, how we might have begun the rather uniquely human process of mentalism (being able to understand from someone else's point of view) - McDougall uses the paradigm of persistence hunting to tell us who we are.
(Here's a link to a youtube video of a persistence hunt by the Kudu, narrated by Attenborough himself - well worth a look!)
After reading Born to Run, I bought myself some VibramFiveFingers and started running again. I'm not the best runner, but I've noticed since stopping wheat and milk (except butter), I never get stitches in my side anymore. I used to get them with nearly every run, no matter how hard or long I trained. They tended to go away after about 30 minutes, so as long as I could "power through" the pain at the beginning, I could get in a nice long run. One doesn't get through medical school and residency without a bit of tolerance for unpleasantness and pain. It doesn't necessarily make you wise, but it may make you tough. The other day my husband made pizza, and (moderation being my motto - I have wheat maybe twice a month), I had a few slices. The next morning, I couldn't do my usual sprints - stitches in my side! Remarkable, that. Don't know if it is the wheat or the cheese. Butter seems to not have the same effect. But I've digressed.
I don't do too many long runs anymore. I try to work out most days a week, but it is mostly weights, sprints, long walks or hikes, and the occasional 5K in the neighborhood. Turns out that long, hard runs (or any long, hard cardio workout, such as a hard-going 115 minute spin class) may be bad for you.
I know. It is hard to fathom. I even looked at the studies a few times before I believed them. Here's one of them. Here's an article about another. Turns out, a lot of marathon runners have crappy, plaque-filled coronary arteries. I'm no radiologist. But Kurt Harris is, and his blog post (and the follow up is here) explains the studies better than I ever could.
My mother had a copy of Aerobics for Women by Kenneth Cooper. Mrs. Cooper writes a lot of the book (I suppose to make it more accessible to women), and she describes how, in the 60s, no one exercised, and her husband Dr. Cooper was the neighborhood freak who loved to jog. The conventional wisdom at the time was that exercise was probably bad for you. (The book also had an exercise program for the "young, dating girl" that counted Friday night's dancing date as part of your points for the week. I should watch more Mad Men).
So is exercise bad for you? Aren't we born to run?
No, and yes, but not born to run long distances very fast. Mark Sisson explains all of this very well in his terrific book, The Primal Blueprint: Reprogram your genes for effortless weight loss, vibrant health, and boundless energy Chris McDougall in Born to Run reports on a persistence hunt where the runners went 10 minute miles. 10 minute miles aren't too fast for hearty, healthy people who run their whole life long. Mark Sisson breaks it down so that for any "chronic cardio" the best thing is to keep your heart rate below 75% maximum (in general, 220 minus your age X 0.75). For most of us, that means a leisurely bike ride, a brisk walk, or a light jog. Chronic hard cardio raises cortisol, stress, and inflammation. Evolutionary Psychiatry is all about anti-inflammation.
Exercise is good for the psyche! No question (1). Regular, 5 times a week moderate exercise caused the remission of mild or moderate depressive symptoms in 42% of those who did it for 12 weeks. Here's another well-known study from 2000. From an evolutionary medicine perspective, we are meant to move.
Does exercise help you lose weight? Well, "chronic cardio" probably doesn't (also, it's not good for you). We tend to eat more to offset the exercise that we do. High intensity interval training (HIIT) definitely does help fat loss (2), and weight training increases muscle mass (thus increases the metabolism and aids in fat loss). Hikes and walks are excellent for the soul, and the more "basic" fitness (the more time you spend walking and hiking, etc.), the more you can push very hard on those once or twice a week sprints to maximize the fat loss. Just steer clear of the chronic, hard-going cardio. Or keep it to a few times a month. Suffering may be good in moderation.