Book excerpt: In The Great Fitness Experiment, a funny and informative guide through the morass of contradictory claims and information in today's health/fitness-obsessed world, Charlotte Hilton Andersen goes from gym rat to lab rat, trying a new workout each month for a year in an attempt to discover what works, what doesn't and what's just plain weird. She delves into such subjects as the Action Hero Workout, Cross Fit Training, Going Vegan, Double Cardio, and others. Interspersed between the chapters on the monthly experiments, Andersen offers personal essays on everything from her past experiences with eating disorders to testing the ugliest fitness shoes on the planet to lesson about, as she puts it ''what I've learned from being a girl in our body-obsessed culture.'' She writes candidly about her history of anorexia, orthorexia and ''general-low-self-esteem-exia'' and includes anecdotes about the effects of the ''health'' craze on my students, friends and gym buddies. In addition, she scours the most recent research to let readers know whether drinking milk after weight lifting really does build more muscle (yep!) or if it matters whether you do cardio or weights first (nope!). She also tests some of the stuff readers have heard about and secretly wanted to try but would never embarrass themselves doing. Readers get all the entertainment and none of the carpet burns as Charlotte bends it like a ballerina, squats like a sprinter, gets hemorrhoids like an Olympian, and HOO-ah like a Navy seal. By the end readers will have new ideas about how to eat healthier, work out smarter, and hold their own in a Photo-shopped world.