Jillian Michaels is a frustrating example of the rise of pseudoscience, because she is both popular and effective.  Unfortunately, her most recent book is a mind-blowing combination of fuzzy logic and pseudoscience, because Michaels has helped a lot of people, and her advice is generally sound.

Jillian Michaels is a fitness expert and personal trainer who really skyrocketed into the public eye as the strength trainer on the television show "The Biggest Loser."  She has parlayed that television success into other media, including a wildly successful website, a radio call-in show, and a series of popular weight loss and exercise advice books.

In general, Michaels' advice boils down to "eat better and exercise more."  The only surprise is how surprising this message is!  As a fitness trainer, Michaels (who bills herself as "America's Toughest Trainer") tends to lean harder on the "exercise" part of the equation, with a variety of methods including her new video game Jillian Michaels Fitness Ultimatum 2009 for the Nintendo Wii.

Although Michaels is constantly emphasizing that there are no gimmicks or shortcuts to weight loss - just hard work, exercise, and eating right - her most recent book completely contradicts that mandate, by insisting that if you eat right, you can reset your metabolism, and lose weight almost magically.  The promise of "mastering your metabolism" sounds too good to be true, and if it was being proposed by anyone other than Jillian Michaels, I would dismiss it out of hand.

This promise that eating the right foods will magically get you to burn weight has been held out by every diet quack of the last hundred years at least.  In the case of Master Your Metabolism, Michaels picks on certain classes of chemicals.  The kinds of things that hippie authors call "toxins."  According to Michaels, these chemicals affect your hormones, and your hormones in turn affect your metabolism.

The biggest problem with these claims is that we still have very little scientific data on how hormones work, much less how they interact with your metabolism.  This is an area in which endocrinology is in a sense still an emerging science.  Our endocrine systems are fantastically complicated, and anyone who says otherwise - or who claims to have mastered their own - should rightly be viewed with skepticism.

For the most part, Master Your Metabolism seems harmless.  In general, it seems to primarily commit the logical fallacy of confusing correlation with causation.  (And bizarre jargon like "antinutrients.") People who eat processed foods are more likely to be obese; therefore, processed foods must cause obesity.  

You can see the logical fail here, but at the same time, there is certainly some causation there.  Processed foods tend to be higher in fat and calories than "real" foods, and keyed to have a carefully constructed taste and structure (like the "mouth feel" of potato chips and dip) that encourages you to eat more.  

This is the main reason why I don't completely decry Michaels' latest book.  The whole entire book is a treatise on why you should eat more fresh fruits and vegetables and exercise more.  Hard to argue with that, even if it is backed by a load of pseudoscientific bollocks.