green juice smoothie
Thinking of trying a cleanse? Here's why you shouldn't.
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  • Cleanses and detox diets are popular, but they're expensive and don't have any lasting health benefits, two nutritionists told INSIDER.
  • Your body can detox itself without any assistance from cleanse diets.
  • Cleanses may also lack important nutrients — and starving yourself of those nutrients can make you feel awful.
  • Plus, once a cleanse ends, you'll likely gain back any weight you've lost.

Cleanses and detox diets are a comforting idea. They're marketed like an insurance policy against junk food benders — a natural way to flush away evidence of overindulgence.

"Going on a cleanse gives people something that they can control — it makes them feel like they're making up for their 'mistakes' in eating," registered dietitian Rachael Hartley told INSIDER. "It's sort of like a coping mechanism to deal with shame that someone feels for eating in a way they think is bad."

This premise is so attractive that people submit themselves to punishing regimens like the Master Cleanse, in which participants consume nothing but a mixture of water, lemon juice, cayenne pepper, and maple syrup. More modern cleanses may appear gentler, since they often feature foods perceived as virtuous, like green juices or teas.

But they still operate on the same premise: That by eating or restricting certain foods for a certain period of time, you can achieve a state of enhanced inner cleanliness.

The only problem is that the human body doesn't work that way. Read on to learn exactly why cleanses won't really cleanse you — and why you shouldn't try one.

1. Your body is detoxing all the time, no matter what you eat.

Detoxing happens even when you eat "bad" foods.
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The biggest strike against cleanses is that they're almost always unnecessary.

"Our body is able to cleanse or detox itself by using normal bodily functions," Hartley said. "When we breathe, when we go to the bathroom, when our liver is functioning — the body does all the cleansing and detoxifying itself. There's no need to follow a certain diet plan to do that."

The work of detoxifying is primarily done by your liver and your kidneys. Unless there's something wrong with those organs, they're going to keep on filtering out waste and toxins whether you eat a salad or a double bacon cheeseburger.

Sure, there are plenty of good reasons to eat salads, like their abundance of fiber and nutrients. And the American Academy of Nutrition and Dietetics notes that a diet rich in fiber and plant foods actually does support the body's existing detox process. But that doesn't mean a specialized diet is required to clear toxins from your body. That's the key takeaway here.

There are a few caveats to mention: Hartley noted that elimination diets — which may look like a cleanse or detox — could be appropriate when it comes to certain medical conditions.

"These should be done under the direct supervision of a dietitian or other medical provider, and an ethical provider will discuss the risks of undertaking such a strict diet," she said.

And registered dietitian Georige Fear added that, before a colonoscopy, a doctor may put you on a diet that will clear your bowel.

"That will definitely help clean your insides out, and help the doctor see what he needs to," Fear told INSIDER. "That is the only good reason [for a cleanse] I can think of."

2. You may miss key nutrients — and you'll probably feel like crap.

Cleanses can leave you fatigued and moody.

"Most of the detoxes I've seen are very inadequate in fat and protein and carbohydrates as well," Hartley said. "[They're] just inadequate in calories."

Fear agreed. "Cleanses often are very, very low on calories, carbohydrates fats and protein," she said. "Many are based on fruit and vegetables or their juices, so you might take in enough vitamins A and C, but cleanses typically would be deficient in calcium, B vitamins, iron, essential fats and zinc, among other nutrients."

Eating too few calories, in particular, can make you feel awful all over, causing headaches, moodiness, weakness, and constipation, as INSIDER previously reported. And Hartley added that cleanses can be especially rough on your brain. Fat is crucial for optimal brain function, and carbohydrates are the brain's primary source of fuel, she explained — so things can go awry when you're on a cleanse that runs low on one or both nutrients.

"A lot of clients who have done cleanses or detoxes in the past have told me how they felt very low energy, fatigued, that it increased moodiness, that they felt more depressed," she said. "And a lot of that has to do with the fact that their brain is eventually being starved for nutrients."

"[A cleanse] is stressful, and being hungry amd headache-y could make for a miserable week," Fear added.

3. You'll likely gain back any weight you lose.

A cleanse might make you lose weight temporarily.
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Plenty of cleanses promise quick weight loss. But Hartley and Fear explained that the majority of weight loss during a cleanse comes from shedding water weight — and it won't last.

Here's a quick primer on water weight: Whenever you eat more carbohydrates than you need, your body stores some of the excess in your muscles and liver. This stored formed of carbs is called glycogen, and in your body, each gram of glycogen is bound to up to four times its weight in water, nutrition professor Dr. Marion Nestle explains in her book "Why Calories Count."

If you start to operate at a calorie deficit— for example, when you're on a restrictive cleanse — your body taps into that store of glycogen for energy, releasing all that bound-up water via your urine. The number on the scale goes down, but there's just one catch.

"Within two to three days of eating normally, your body will return to its normal weight and shape," Fear said. "If you haven't changed your eating habits permanently, it won't have any lasting impact."

4. Cleanses can be wildly expensive.

A cleanse might clean out your wallet.

Premade juice and soup cleanses can have staggering price tags — think $65 to $79 for one day's worth of food. DIY cleansing isn't always cheap, either. A single day juice of at-home juicing could set you back about $40, Business Insider reported.

None of this is to say that the foods you might eat on a cleanse are "bad." If you genuinely enjoy green smoothies or raw vegetables, there's no reason to stop eating them. But subsisting on only green smoothies for an arbitrary amount of time won't won't magically flush out your body. At best, it'll be pricey and unnecessary. At worst, it'll leave you feeling miserable.
