I read an article in the newspaper about a new book by Jim Karas, "The Cardio-Free Diet". In this piece by ABC News, Karas states that, "cardiovascular exercise kills a weight-loss plan, your internal organs, your immune system, your time and your motivation. If your true goal is to lose weight, interval strength training is the only way to go."
Wow, cardio kills your internal organs and your immune system? That's a new one. Of course, he's getting this from the few outliers who perform too much aerobic exercise, like marathoners. But the idea that appropriate cardio "kills" is a joke; it's just some marketing hype to help him sell books.
And what's so great about interval weight training? It's certainly a sound technique, but circuit training has been around since the 1960s. I am unaware of any studies that show huge weight losses with circuit training. Compared to this study by Ross et al, 60 minutes of daily aerobic exercise without dietary restriction led to a weight loss of about a pound per week.
And if "interval strength training" is so effective, then why wouldn't plain old (aerobic) interval training be just as effective for losing weight? The reality is that interval strength training can be effective for losing weight only because it mirrors aerobic interval training. In other words, it's the process of engaging major muscle groups at high-intensity for a brief time, resting, and then repeating that burns calories. This is what can lead to some weight loss - not the fact that the intervals used are strength training intervals.
Also, the idea that we are made for a cardio-free life has no bearing to our evolutionary past. How would a hunter acquire any game by sitting in one spot and by performing something resembling interval strength training? The short answer: he wouldn't. Hunting means locomotion - getting out there walking, sprinting, and chasing game. Not lifting rocks and waiting for food to magically appear.
I recommend taking a pass on this book. The time spent reading it would be better spent performing aerobic exercise!
