The word "detoxification" is flung around the fitness community as frequently as kettlebells are swung.
Yoga teachers regularly speak of detoxifying twists, aerobics instructors of detoxifying sweat, dieters of detoxifying fasts. But health professionals are skeptical.
"If you start talking about exercising to detoxify, there's no scientific data," said Dr. Elizabeth Matzkin, chief of women's sports medicine at Harvard Medical School. "The human body is designed to get rid of what we don't need."
The same applies to fasting.
"No good scientific data supports any of those cleanses, where you drink juice, or (only) water for a week," she said.
Exercise is important, Matzkin added, because it enables our body to do what it is made to do, but the kidneys and colon get rid of waste. The role of exercise in that process is unclear.
"In general exercise helps our lungs; kidneys get rid of things that can cause us onset of disease," she said.
A healthy lifestyle - eating healthy, drinking plenty of water and exercising - is important to detoxifying because it enables our body to do what is intended to do.
"As for specific yoga moves, I'm not so sure," she said.
Yoga instructor and fitness expert Shirley Archer, an author and spokeswoman for the American Council on Exercise (ACE) said the theory behind the effectiveness of detoxifying twists in yoga is that they squeeze the organs, which push the blood out so fresh blood can rush in.
"Better circulation equals better health," said Archer, who is based in Florida. "If detox means to eliminate from the body what it no longer needs, then certain yogic practices can help."
She said yogic deep breathing with strong exhalations can empty the lungs of unneeded carbon dioxide and allow for a fresh breath of more oxygenated air. "This nourishes all of our cells," she said. "It is also a method of cleansing because better circulation equals better health."
Meditative movement practices, such as yoga and tai chi, she added, can detox your attitude because they require staying in the present moment and discourage dwelling on the past.
Last summer, celebrity trainer Tracy Anderson began taking groups of 40-odd women on what she calls Detox Weeks, which involve at least three hours of workouts each day, as well as lectures on fitness and nutrition aimed mainly at encouraging lifestyle changes.
Similar weeks in other cities are planned for 2013.
"Women work out and think 'Why can't my love handles, muffin tops go away'?" said Anderson, creator of the Tracy Anderson Method and a co-owner, with actress Gwyneth Paltrow, of fitness centers in Los Angeles and New York. "The most important thing is if you can become a consistent exerciser."
"A good workout is not five to 10 yoga poses," she explained. "You have to learn to scale up your endurance. If you can only jump for five minutes straight, we'll go to 10 minutes, then 20 minutes."
Anderson said she uses the term detoxification broadly to include everything from working up a good sweat to clearing the mind of destructive thoughts.
"Detoxification is a big topic," she said.
Nancy Clark, a registered dietitian in Boston, Massachusetts and a member of the American College of Sports Medicine, said the body generally does a fine job of detoxifying itself through the liver and kidneys. Sweating has nothing to do with it.
"When you sweat you really don't detoxify anything," she explained. "If someone goes on a crash diet, then maybe toxins are released but then the body would take care of them. When you sweat you lose sodium."