It seems like everyone is removing something from their daily diet these days—gluten, sugar, carbs, fruit...the list goes on. Or in some cases, they're shunning food altogether. Why are elimination diets -- like detox and fasting -- so popular? And how well do they work?

First there was the eye-catching photo of a bikini-clad celeb cradling her newborn above her perfectly toned abs. In the interview, she says her amazing body and incredible energy are all thanks to her juice cleanses. Not long after, I was sitting on my couch one night, cradling my goblet of red wine, and a TV diet doc starts spouting all kinds of scientific-y terms—like ketones and toxic loads—and promises his intermittent fasting and detox diet will take 10 pounds off my waist and 10 years from my face. (And I can buy his book right now for just $19.95!)

We've heard about detoxes, cleanses, and fasts for years, of course. But now it seems like all of Hollywood is embracing them as ways to lose weight, make their skin glow, and get energized. Energy from fasting?! It seems counter intuitive, so I turned to the science.

Photo by Meredith

Detox: Clearing the Way

Many people fast when they feel a need to detox—that is, rid their bodies of toxins, medications, an overabundance of food and/or alcohol, etc. A detox diet is typically extremely low-calorie and involves specific foods such as juices and other liquids, all geared to "clear out the pipes."

There are hundreds of detox diets, but one of the oldest and most famous is the 76-year-old Master Cleanse. While Beyoncé supposedly credits the diet (which consists mostly of drinking lemon juice with cayenne pepper and maple syrup) for her quick 20-pound weight loss before starring in Dreamgirls, the diet was developed, according to its creator, "to simplify the cause and the correction of all disorders." All disorders? Wow!

Like Master Cleanse, other cleansing diets promise much more than just weight loss. Dr. Mark Hyman's 10-Day Detox Diet, for example, claims to radically reboot your entire body, because, he says, "What we're eating makes us sick." When you follow his plan and eat "real food," he claims, you'll "take back your brain chemistry, hormones, and activate your fat-burning genes." As with most cleanses, it's very high in fiber.

Detox diets claim to rid your body of toxins by cleaning out your colon, liver, and kidneys, generally thanks to some combination of juice, supplements, and raw foods. But the truth is, all three organs already do a great job of filtering toxins and flushing waste.

On the other hand, who hasn't gone through a period when you feel like you've been eating too much rich, sugary, or junk food—or just eating too much? Or maybe you've been taking a lot of medications, or drinking more than you should. A detox diet may be just the psychological jump start you need to get back on track. Some people experience euphoria with fasting and feel purified and ready to live more "cleanly"—while others report nausea, irritability, bloating, stomach cramps, and worse. There's only one way to find out which group you'll be in....

The "Fast" Way to Lose Weight

For many years, conventional wisdom was that fasts—eating less than 25 percent of your normal daily calories—cause only temporary "water weight" weight loss. But a number of studies are finding otherwise.

In a recent review, researchers found that intermittent fasting (a set number of days each week) resulted in sustained and continued weight loss similar to that of participants who restricted their calories less, but daily. (In other words, the way most of us diet.) Fewer study participants dropped out from the intermittent-fasting diet than from the more-traditional diet program. For some, it may be easier to stick with barely eating for a couple of days than the ongoing drudgery of daily dieting. These were small studies, so the results are far from conclusive, but they do show there may be weight-loss value to intermittent fasting.

Fasting may work better for some people than others. If you like consistency and do well on a steady regimen, intermittent fasting may not be for you. But since my job requires me to eat out a lot, I like the idea of fasting on my non-event days and eating normally when I go out.

Cleansing the Spirit

Fasting plays an important role in most religions. Some people feel fasting gives them clarity of thought, that it's spiritually cleansing and purifying. Jews fast to atone, Buddhists to purify. Catholics do it to control carnal desires and to do penance, Hindus to enhance concentration, and Muslims to prove piety. There are as many spiritual reasons to fast as there are religions.

The argument could be made that if fasting enhances your spirituality, it may also contribute to your good health. After all, there is ample evidence that faith can help with good health. Perhaps the "high" so many people say they get from fasting comes from that awakened spirituality. Or maybe it is akin to a runner's high—after all, both running and fasting require your mind and body to collaborate in a show of willpower.

And while we're talking about willpower, some advocates believe fasting strengthens it, as well as discipline for other parts of their lives. In truth, many fasting advocates are so devoted to their belief in its benefits, they feel it can cure nearly anything.

Good science won't stand behind that, of course, although there is some early evidence in animal studies (enough to merit more research, anyway) that intermittent fasting just may help with insulin resistance, Alzheimer's, heart disease, and longevity.

While it is much too early to make any of those claims, the science is more promising that an every-other-day fast really can help you lose weight and keep it off. And, hey, if it gives me the flat belly, glowing skin, and increased energy that proponents say it will, I'm all for it.

Diet Details

So what do these diets actually involve? Here are details on some of the most popular detox/diet approaches.

The Master Cleanse

For 10 days: First thing in the morning, drink 1 quart water with 2 teaspoons non-iodized sea salt. In addition, mix and drink at least six times per day: 10 ounces of water with 2 tablespoons lemon juice, 1 to 2 tablespoons maple syrup, and a pinch of cayenne. Lastly, drink a laxative herbal tea in the evening.

The 5:2 Diet

Eat normally for five days a week. The other two days, restrict your intake to 25 percent of your calorie needs, or about 500 calories.

The Every Other Day Diet is based on solid, though relatively small, studies. You consume 500 calories every other day, and other days eat whatever you want. According to author Krista Varady's research, participants ate about 10 to 15 percent more calories than usual on their non-fasting days, which still left them well below their normal weekly consumption. Dieters in her study lost about 13 pounds in eight to 10 weeks.