What came to be called "The Great Fitness Experiment" began four years ago.

Having just given birth to the third of her five children, Charlotte Hilton Andersen of Lakeville decided she wanted to lose weight, preferably by the healthiest and most effective methods available.

But what were those?

Andersen's science background -- she's a former teacher of chemistry and computer science -- inspired an approach that's methodical, if not strictly scientific. She decided to test a different diet or exercise plan every month.

So one month she tried kettlebells. Another month, she went vegan. Another, karate. Andersen plunged into researching the latest fitness plans, grabbing ideas from books and the Internet. She tried programs called "CrossFit," "the Primal Blueprint," "Double Cardio" and "The Action Hero Workout." She studied the advice of celebrity fitness experts, from Madonna's trainer to Jillian Michaels of TV's "The Biggest Loser."

Her husband, Jason Andersen, 35, watched with bemusement as exotic workout devices piled up near their kitchen.

"I said, 'Is this some kind of medieval torture system you've set up?' She said, 'No, it's my exercise equipment.'"

Friends and relatives wanted to hear about her results and, to avoid repeating the same stories over and over, she started blogging After a year, she had the basis for a book.

Published in January, "The Great Fitness Experiment: One Year of Trying Everything" is a chatty and funny account of her trials, featuring a cover photo of the 32-year-old author in pink and black spandex, standing inside a huge lab beaker.

But the experiment continues, and is still being documented on Andersen's blog.

Most of the fitness plans have been rewarding, or at least interesting, and some outright fun. A few, however, were duds. A diet modeled after the supposed eating habits of Neanderthals left Andersen so famished that she binged on Little Debbie Honey Buns. The double cardio program's relentless workouts actually caused her to gain body fat -- a surprising but not uncommon phenomenon, she has since learned. Apparently the body senses when it's being overtaxed and issues a metabolism lockdown.

Meanwhile, Andersen says she has learned "200 ways to publicly humiliate myself," including the time she accidentally snapped herself with a jump rope and split open the back of her spandex pants, an episode she says her gym friends have yet to let her live down.

She laughs at those mishaps. But as she recounts in her book, more serious problems developed when Andersen, who tends to "do everything at, like, 110 percent," followed her diets and workout programs too zealously.

"Part of this whole process was I got a little too sucked into my research," Andersen said. "I think we have this mentality in our country that anything that you can do to lose weight or, quote, 'get in shape' is good."

So, for example, on a mission to eat vegan she wound up eschewing not only animal products but, eventually, most other foods.

"Tropical fruits were too high in sugar," she said. "And it was one thing and another, until finally it got down to about five foods that I would eat. I couldn't go out to eat. I couldn't go to friends' houses if they were going to serve food."

She wound up appearing on TV's "20/20" to discuss the unusual disorder that her therapist called "orthorexia." Therapy brought her back to normal eating. After that, to be safe, she decided to focus her research on exercise, not diets. What could go wrong ... right?

Well, a year later, she found herself working out strenuously for three to four hours a day.

She didn't consider it a big deal (contestants on "The Biggest Loser," after all, work out more than twice that long, she said) until the day when, after running a marathon, she proceeded to the gym for an hour of kickboxing, then fainted.

"I felt like I was going to die," Andersen said. Until then, she hadn't even recognized a problem. "Nobody will ever tell you that you're working out too much. You'll be there for six hours a day and people will say, 'Oh, I wish I had your resolve,' 'I wish I were as strong as you.'"

At one point, she became "scary skinny," dropping 60 pounds below her starting weight. Her periods stopped, she felt cold all the time, she was tired and hungry.

And, most disturbing, she kept getting compliments on how great she looked.

"I hate that the world I live in is so messed up that everyone thinks I'm beautiful even when I'm cold, tired and hungry," Andersen writes in the book.

These days, Andersen throws herself 110 percent into ... moderation. She doesn't diet, doesn't weigh herself regularly, limits herself to an hour of exercise a day, won't watch "The Biggest Loser."

But Andersen and her gym buddies are still testing new exercise programs every month.

"You would think that eventually I'd run out of new things to try, but people keep coming up with new stuff," she said.

Her gym buddies say they've enjoyed the variety, not to mention achieving impressive levels of fitness.

"I never thought I'd be able to do a pull-up, and today I did three," said Megan Seiler of Lakeville, who has joined Andersen for much of the ride.

Andersen avoids making blanket fitness recommendations ("I'm not a doctor"), but says that in her own experience, a combination of interval training and weight lifting are especially effective for quick shape-up. Her good news -- or bad, for those who'd prefer a magic formula -- is that just about any exercise plan works if you follow it. Since long-term consistency is key, she suggests picking something you enjoy.

"I think people need to focus on what's fun for them," she said. "Don't force yourself to run 10 miles if you're a dancer at heart."

Katy Read is a Twin Cities freelance writer.