(Kirk McKoy / Los Angeles Times / June 8, 2012)

To the rational mind, the notion of willingly depriving oneself of food for days on end seems illogical, at best. Basic biology, after all, dictates that calories are necessary to sustain everyday functioning and that low levels of, say, iron or potassium could throw off our physical health, possibly even dangerously so.

And yet, extreme dietary cleanses seem to have gripped the imaginations of even the most practical among us. Somewhere along the line, we bought into the idea that our bodies harbor toxins that need flushing out or that dropping weight via an all-liquid diet is someone medically sound.

So how have these regimens become so popular? What's so enticing about them? And do they actually do any good?

Kinds of cleanses

For anyone looking to embark on a cleanse, there's no shortage of options: juice fasts, water fasts, lemonade diets. A company called BluePrint Cleanse, for instance, sells three- to 10-days worth of juices made from ingredients such as kale, cashew nuts, apples and pineapples. Another, Ritual Cleanse, follows a similar program of organic raw juice, promising on its website potential benefits that include mental clarity, weight loss and increased sex drive.

For the star-struck among us, there are celebrity-endorsed cleanses. Gwyneth Paltrow, the incurably buoyant actress and mother of two, swears by the Clean Program, a 21-day eating plan consisting of a shake for breakfast and dinner, and a light lunch. Salma Hayek co-founded the Cooler Cleanse, a program that professes on its website: "Consuming only liquids for a few days frees energy in the body, which can then return to the essential jobs of deep inner cleansing and healing."

And then there's the Master Cleanse, which tells users to ingest only a mixture of water, lemons, cayenne pepper and maple syrup up to six times a day for 10 days.

The big draw

Teddy Bass, an L.A.-based personal trainer who works with celebrities, notes that one reason cleanses have caught on is because of our belief as a society in the lifestyles of the rich and famous.

"This is a fad-oriented society," he says. "If people read that someone got results from doing this for a certain amount of days, then they really want to do it."

Psychiatrist Megan Jones, director of the Healthy Body Image Program at Stanford University, adds that even those of us who might otherwise be above the hype can get ensnared in a clever marketing ploy — on the emphasis that cleanses place on "health."

"'Healthy' is becoming a pseudonym for 'dieting,'" she says. "The advertising industry is using health as a way of selling an unrealistic and unattainable ideal. For very smart, well-educated people, it's not socially acceptable to go on a diet." A cleanse, she adds, sounds more in line with taking care of one's body.

What the pros say

So is there anything healthy about a dietary cleanse? Dr. Adrienne Youdim, the medical director of the Weight Loss Center atCedars-Sinai Medical Centerin Los Angeles, doesn't think so.

To begin with, she says, our bodies are equipped with everything they need to rid themselves of bacteria, chemicals or viruses.

"The body actually has a very intricate way of detoxing on its own," she says. "Our liver is designed to clear toxins out of the body. Our kidneys are designed to clear toxins out of the body. Our gastrointestinal tract itself has mechanisms to clear toxins from the body. There really isn't any reputable science to suggest that there is any health benefit" to cleanses.

As for the weight loss promised by a week of liquid dieting, Youdim notes that any poundage shed on a cleanse is likely to be temporary. What's more, she adds, cleanses done repeatedly might actually cause the practitioner to gain weight in the long run.

"The weight loss is often not the kind of weight that you want to lose," she says. "You may be losing lean mass, and when that comes back it comes back as fat. If these are done recurrently, the long term would be changing your body composition for a higher percent of body fat."

So why do it?

The question remains, then, as to whether cleansers know that there isn't much science behind their diets and do them anyway, don't know about the lack of science at all or simply don't care about the science.