Fitness guru Jillian Michaels was a train wreck. Sure, "television's toughest trainer" could work weight-loss miracles on the series "The Biggest Loser." But off camera, she was burning the candle at both ends, trashing her body in the gym and living on processed foods, artificial sweeteners and caffeine.

"My hormones were entirely whacked and with it, my metabolism," Michaels said.

Now the 34-year-old says that hormonal imbalances are a big reason why women struggle to lose weight, even as they're ruthlessly dieting and exercising. Her journey back to health, which she details in her latest book, "Master Your Metabolism" (Crown, $26), involved making diet and lifestyle changes to rebalance her hormonal levels. "People think they've been handed a sentence of having a 'slow metabolism' and there's nothing they can do," said Michaels, who wrote the book with endocrinologist Christine Darwin and medical researcher Mariska van Aalst.

The straight-talking Michaels elaborated for us by phone from her home in Los Angeles.

Q: What is "metabolism" to you?

A: It's your biochemistry, the symphony of the hormones that tell your body when to eat, what you're craving, what to store as fat and what to burn as fuel. You can't just boost one hormone; you have to balance them. It's like an orchestra. If you tune the violin but not the trombone, it's all screwed up.

Q: How can you speed up a slow metabolism?

A: Get more sleep. Fill up on fiber so the body produces more leptin, which makes you feel full. And when you're trying to lose those last 10 pounds, the body gets panicky and shuts off your metabolism, so you have to incorporate weight training. It's critical in releasing growth hormone, which burns fat.

Q: Why is sleep important?

A: It increases human growth hormone and leptin (which tells the brain to turn off hunger). It inhibits the release of ghrelin (a hormone that tells the brain you're famished) and cortisol (stores fat).

Q: What changed after you got your hormones balanced?

A: I was working out eight hours a week, eating 1,200 calories a day and exhausted all the time. Now I feel healthier than ever and I'm able to maintain my physique by working out three to four hours a week and eating 2,000 calories.

Q: What's the biggest mistake at the gym?

A: Underestimating their ability and not pushing themselves. If you want to release fat-burning hormones, you have to get your heart rate up. If you're not pushing, you're not burning enough calories to make a difference, so you're wasting time. You also won't get results, which can be discouraging. People say they "went to the gym," but then they walk 3 miles an hour at no incline.

jdeardorff@tribune.com