In his new book, “What Happened to Moderation?” Dr. Stephen Brewer says that Americans are drawn to extreme health care choices, just as they gravitate toward political extremes and non-stop work patterns. In today’s episode, Dr. Brewer, medical director at the Canyon Ranch Wellness Resorts, advises us to back away from trendy, over-the-top diet and exercise routines. It’s time, he says, to look at common-sense approaches to improving our health and treating routine illnesses. Exercise is vital to fitness, and fitness is a key to career performance, but that doesn’t mean you need to run marathons.