The worst fad diets for your brain and body, from the bible-inspired Daniel Fast to the werewolf diet

Actor Chris Pratt has done the Daniel Fast, which requires eating only fruits, vegetables, and unleavened bread for 21 days, as well as praying every day.

The goal of the diet, according to its website, is to help dieters "focus on their health using Christ-centered teachings," but limiting food intake so severely could prevent a person from getting all of the nutrients they need. There is no science-backed evidence this diet works, either.

Created in 2009 by then husband-and-wife pair Melissa and Dallas Hartwig, the premise of the monthlong Whole30 regime is that if you put only "good" things in your body you'll feel better, reduce inflammation, and transform your relationship with food. Whole30 dieters are restricted to eating only fruits, veggies, meat, seafood, eggs, and some fats including avocados, cashews, and olive and coconut oil.

It's a tremendously popular plan on Instagram, where people post colorful photos of their veggie and fruit-filled #Whole30 plates.

But Whole30 isn't really supported by science; nutrition experts say it takes more than 30 days for your body to perform a truly complete re-set if you want to reduce inflammation. Besides, fiber-rich foods, which the Whole30 diet strictly limits, can actually improve inflammation markers and help stave off all kinds of diseases.

Created in 2009 by then husband-and-wife pair Melissa and Dallas Hartwig, the premise of the monthlong Whole30 regime is that if you put only "good" things in your body you'll feel better, reduce inflammation, and transform your relationship with food. Whole30 dieters are restricted to eating only fruits, veggies, meat, seafood, eggs, and some fats including avocados, cashews, and olive and coconut oil.

It's a tremendously popular plan on Instagram, where people post colorful photos of their veggie and fruit-filled #Whole30 plates.

But Whole30 isn't really supported by science; nutrition experts say it takes more than 30 days for your body to perform a truly complete re-set if you want to reduce inflammation. Besides, fiber-rich foods, which the Whole30 diet strictly limits, can actually improve inflammation markers and help stave off all kinds of diseases.

Madonna and Demi Moore are both reportedly fans of this loony lunar plan, which dictates when dieters should eat based on the sky above.

"The basic iteration calls for 24 hours of fasting during the full moon or new moon, when you’re permitted only water and freshly squeezed fruit and vegetable juice," according to US News and World Report.

But remember, just because the moon helps push around the Earth's tides doesn't mean it has any effect on your own body weight.

This diet plan is as terrible as you might've guessed: replace two meals a day with roughly a dozen jars of baby food, and you can have a normal, adult-sized dinner. Though people have been speculating that stars adhere to this diet for years, there's really no evidence anyone in Hollywood is actually going bananas for baby puree.

Jennifer Aniston told People magazine in 2010 that despite the rumors of her being on the diet, "I’ve been on solids for about 40 years now."

"Sorry, but the last time I had baby food, I believe I was 1," the former "Friends" star said.

The diet plan, popular in the early 2000s, was billed as a way to gear up for swimsuit season in a hurry by replacing two daily meals with a cup of Special K cereal and half a cup of low fat milk.

The plan was promoted by Kellogg's cereal company for years as a research-backed way to be "slimmer for summer" but they've scrubbed all traces of it from their current website.

Subsisting on a cereal-based diet can push people to miss out on key nutrients and illness-fighting compounds that are abundant in plants like fruits and veggies. Besides, Special K doesn't have a ton of fiber in it, so you'd probably do better to try out some other cereals that are less processed.

Eating a diet without gluten, a protein found in carbohydrates like bread and pasta, is often touted by believers as being healthier than gluten-filled diets, but research has only shown doing so is beneficial to people with Celiac disease.

In fact, carbs with gluten contain more fiber and promote heart health than carbs without gluten, so you'll have to up your intake quite a bit to get your daily requirement the gluten-free way.

Paleo dieters subsist on meats, fish, fruits, vegetables, nuts, and seeds, while shying away from grains, sugar, dairy products, and anything processed. Paleo aficionados argue that this diet is what our bodies are built for, and that modern farming has evolved faster than our guts.

Scientists, however, disagree about the merits of the plan. Paleo dieters who often fuel up on heavy doses of proteins like meat put themselves at risk for vitamin D deficiency, and may not get enough calcium for their bones to stay healthy. There aren't really any long term clinical studies on the benefits or risks of the paleo diet, either.

UC Davis Health dietitian Alex Nella encourages his patients who are excited about paleo to make some modifications to the standard paleo diet: adding beans, lentils, whole grains, and dairy onto their plate.

"I also recommend that they carefully choose protein sources, emphasizing quality over quantity," he said in a Q&A.

The diet was first invented in the 1800s when a doctor said he cured his jaundice by eating raw apples. Today, people who do a raw diet typically eat 75% raw foods, which are foods that haven't been cooked, processed, microwaved, irradiated, genetically engineered, or exposed to pesticides.

The problem is, humans have evolved to eat certain foods that are cooked first and people on the diet could get just half of the calories they should be consuming on a daily basis, according to US News & World report. That lack of calories likely means raw food dieters are also skipping out on key nutrients every day.

Raw food eaters who take it to the extreme by consuming raw fish and meat are increasing their likelihood of exposure to harmful bacteria, too.

The TB12 diet includes rules like eliminating foods like potatoes, peppers, mushrooms, tomatoes, and berries. Brady believes these foods, which fall under the "nightshades" category, can cause inflammation.

This idea isn't science-backed, and food-related inflammation is typically not enough to cause adverse health issues like the TB12 diet suggests. Skipping out on so many types of good-for-you produce could result in nutrient deficiencies.

The whole diet is also loosely based on eating alkaline, a largely debunked diet myth that suggests eating foods with a low pH will promote bone health and provide more energy. "If you actually eat a bunch of baking soda — even if you do that — you don't change [the pH level] that much," Mayo Clinic sports performance expert Michael Joyner told Vox.

The TB12 diet also suggests drinking an extremely large amount of water (up to 2.5 gallons daily), which may be helpful to a constantly training athlete like Brady, but can cause permanent brain damage to an average Joe who usually drinks less water.

Besides the obvious meaty choices, other carnivore-approved foods include eggs, fish, and dairy.

Nutritionists don't think this is a good plan, since there's essentially no dietary fiber in the mix and it's missing a lot of key nutrients we don't get from animals, like the beneficial plant chemicals in fruits and vegetables that studies suggest help reduce our cancer risk.

Sure, being a frugivore, and subsisting on fruits, roots, nuts and seeds may work for animals like orangutans, but the human version of this plan — being a "fruititarian" — is probably not the best idea.

Apple co-founder Steve Jobs, who died from complications of pancreatic cancer in 2011, was said to be a fan of this fruity diet, but when Ashton Kutcher tried it in 2013 while preparing to play Jobs in a biopic, the all-fruit plan had some scary effects on his own pancreas.

"I went to the hospital like two days before we started shooting the movie," Kutcher told USA Today. "I was like doubled over in pain."

The pancreas secretes insulin in the body when we eat carbs like sugary fruit.

"If all he was doing was eating fruit, he may have been overworking it," dietitian Keri Gans told US News and World Report of Kutcher.

In addition to posing serious malnutrition and pancreatic risks, the diet is high in sugar, which makes it a disaster for diabetics and can set fruit dieters up for weight gain and tooth decay.

"By relying mainly on fruits and depriving yourself of needed vitamins, fats and proteins, it’s possible to push your body into starvation mode," Cleveland Clinic dietitian Laura Jeffers wrote in a blog post. "If your body feels it’s starving, it will slow down your metabolism in an attempt to conserve energy for vital functions."

All the plant-based meals on this diet are never heated beyond around 104 degrees.

This doesn't make a ton of sense, because fresh foods like carrots and mushrooms can actually be better for you when they're cooked.

The goal of freeganism is to opt out of consumerism.

"Freeganism is a total boycott of an economic system where the profit motive has eclipsed ethical considerations," as the website freegan.info explains. "Instead of avoiding the purchase of products from one bad company only to support another, we avoid buying anything to the greatest degree we are able."

Freegans rely on dumpster diving and "urban foraging," by learning when and where places like hotels and restaurants dump their extras. To survive on this diet, you have to know how to show up in the right place at the right time. Nutritionally, it's probably not so great either, because you have so little control over what and when you eat.

Master cleansers can only consume salt water, laxatives, and tons of lemon water with cayenne and maple syrup. After 10 days (or more) on this diet, followers are encouraged to re-introduce solid foods slowly into their daily regimen, with soups and juices.

Beyonce is reportedly a fan of the plan, and used it to get ready for "Dreamgirls."

Not eating is a proven way to shed pounds short-term, but given that you're using laxatives and starving yourself, the weight loss amounts to a lot of lost water weight and muscle mass. The starvation diet could even slow your metabolism, setting you up to gain more weight back when you finish the cleanse.

Juice and soup cleanses can take a variety of forms, but typically involve a person swapping out one or all of their meals for soup or juice to detox the body. Experts have said that these cleanses cause people to miss out on key nutrients and feel crummy as a result.

Plus, the body has a natural detoxification system in place, so a diet meant to kick-start the process is simply a waste of time and money.

Nutritionists are starting to agree that sugar, not fat, is the real driver of weight gain in our diets.

It's true that more processed versions of lard, like recently-banned trans fats and their alternatives, aren't great. But plant-based oils like olive, avocado, and even fatty fish can be wonderful additions to any diet.

Besides, when food manufacturers drop the fat from their products, they usually add in sugar to amp up the taste, which does not help waistlines in the long run.

As advice meant to help women achieve smaller waists, a Vogue writer published a diet that suggested eating smaller amounts of food but supplementing what you did eat with a bit of champagne." Any diet that cuts calories for a while is a good diet," the article read, but we know now that's not necessarily true and can lead to a lack of essential nutrients.

When cigarettes were a status symbol and marketing of the tobacco product was in its prime from the 1930s through the 1950s, doctors were actually recommending "healthy" cigarette brands for certain health issues.

Lucky Strike brand cigarettes made advertisements suggesting that cigarettes could quell a person's appetite and help them lose weight. Although science has shown that nicotine in cigarettes does suppress appetite, puffing on a cigarette comes with health risks like cancer, lung disease, gum disease, and more.

Sticking a tapeworm in your stomach to eat your food for you can prompt serious complications.

People with tapeworm infections often lose their appetite, crave salt, get diarrhea, become dizzy, and have abdominal pain. In rare cases, tapeworm infections prompt appendicitis, dementia, and even death.

People with worms may also lose a few pounds, but weight loss is not guaranteed. All that a tapeworm can promise you for sure is an infection, which if it explodes beyond the intestines can cause seizures.

Knowing all this, it seems like common sense that people would try to avoid tapeworm infections at all costs, but that's not always the case. One Iowa woman admitted she bought a tapeworm off the internet and swallowed it in 2013, prompting the medical director of the Iowa Department of Public Health to let her know that "those desiring to lose weight are advised to stick with proven weight loss methods — consuming fewer calories and increasing physical activity."

Former Vogue editor Helen Gurley Brown first mentioned the diet in her 1962 book Sex and the Single Girl and it was re-published in the magazine in 1977.

Gurley suggested drinking a bottle of white wine daily, split up into three meals, and supplementing the wine with a hard-boiled egg and coffee at breakfast and two hard-boiled eggs and more black coffee at lunch. For dinner, dieters got to treat themselves to a 5-ounce steak, even more black coffee, and the remainder of the white wine.

Obviously, doing so is bad for you because you're missing out on the majority of nutritious foods you should be eating on a daily basis and subsisting on meat, alcohol, and eggs.

Dieters can also eat limited amounts of fruits and vegetables, beef, chicken, and brown rice during the seven-day period. The diet is usually used to lose weight fast, since it limits calorie intake severely, but doing so isn't healthy or sustainable for long-term health. You could also feel more weak and tried than usual from eating so little.

The diet involves one to two tablespoons of apple cider vinegar daily before eating any meals. Proponents believe that the acetic cid in the vinegar can help boost metabolism and therefore help with weight loss. The apple cider vinegar is very acidic and is diluted before use, usually in water.

Extensive, peer-reviewed research has yet to suggest apple cider vinegar has the ability to promote weight loss, though.

"Sellers of these supplements might claim that their products help you lose weight by blocking the absorption of fat or carbohydrates, curbing your appetite, or speeding up your metabolism. But there’s little scientific evidence that weight-loss supplements work," as the National Institutes of Health says.

At best, they'll do little for your waistline, and at worst, they'll do serious harm.

Unlike prescription drug makers, diet pill makers are largely unregulated: they don't have to prove their cocktails of herbs and minerals actually work, and they alone are responsible for making sure their supplements are safe. However, the US Food and Drug Administration (FDA) sometimes steps in to take supplements off the market, or force manufacturers to change their labeling, if supplement makers are lying about the effectiveness of their product and there's no evidence to support their claims, or if a product is deemed unsafe.

For example, the FDA took Ephedra off the market in 2004. The plant product can suppress appetite and increase calorie burn in the body, stimulating the nervous system and leading to weight loss, but it's also deadly dangerous and can lead to nausea, vomiting, anxiety, mood changes, high blood pressure, abnormal heartbeats, strokes, seizures, heart attacks, and death. Diet pills can also interact with other drugs you may be taking in strange ways, so it's important to check with your doctor before you start popping one.

A diet rich in iodine can help keep your thyroid gland humming along healthily.

Foods that are iodine-rich are typically healthful additions to a diet, like seaweed, cheese, milk, eggs, iodized salt, and fresh saltwater fish.

A condition called hyperthyroidism — an overactive thyroid— can lead to weight loss. But trying to hack your way into good health, by eating a diet extremely high in iodine or popping supplements, is a dangerous strategy.

Not only can hyperthyroidism lead to troubling side effects like muscle fatigue, it can prompt a rapid irregular heartbeat, trouble sleeping, diarrhea, trouble breathing and swallowing, and in some cases, death. What's more, getting too much iodine can actually set certain people up for developing hypothyroidism, which slows down metabolism.

It's best to stick to a more balanced plan, incorporating iodine rich foods into your diet, not relying on those foods (or untested iodine supplements) as one's sole sustenance.

The diet suggests that eating low-acid foods, or more alkaline foods, will help the body obtain a more neutral state and prevent disease. That means dieters can't eat most dairy products and produce like tomatoes because they are considered too acidic.

Experts say there isn't really a way to change the pH level of the body, though. Also, no studies have proven that acid in the blood, stomach, or urine can cause cancer like the diet suggests.

HCG stands for human chronic gonadotropin, which is a hormone that is typically at high levels in the body during early pregnancy. The diet was invented in 1954 by a British doctor and only allows 500 calories per day, which is well below the recommended amount.

The diet is also supplemented with HCG, usually in the form of oral drops or sprays, although when the diet was first invented, an HCG injection was administered.

Studies on the HCG diet have found that the weight loss people experience has nothing to do with the HCG hormone, but simply with the scary small number of calories dieters consume.

The diet was named after its creator, Pierre Dukan, and involves eating a high-protein and low-carb diet in order to lose weight. There are various phases to the diet, and one includes a day where you eat only protein.

Experts have said the diet is restrictive, unsafe, and that there is no proof it is effective for weight loss.

Many people mistakenly believe this diet was developed at General Motors in the 1980s as a weight loss plan for employees, but that's not true.

"We’ve concluded it’s an urban myth," GM spokesman Tom Wilkinson told The New York Times. "It’s a fairly unconventional diet, and in the 1980s G.M. was the most conventional of companies."

The GM diet is a bizarre plan, whoever did come up with it.

The one week diet kicks off with a day of only fruit (heavy on the melons), followed by another that's purely vegetables, starting out with a baked potato for breakfast.

Then the diet moves on to more variety. Both fruit and vegetables are allowed on day three, and then only bananas, milk and soup on the fourth day. Finally dieters round out the week on a more savory note with beef and tomatoes on day five; beef and vegetables on six; and brown rice, veggies, and juice on day seven. No one said this diet made any sense.

Consuming nothing but water will of course lead to weight loss, but doing so can lead to serious nutrient deficiencies, since the diet is essentially a fast.

Although drinking water is important, you must also eat regular balanced meals to stay healthy.

Instead of cabbage soup, Sacred Heart dieters eat a special soup recipe that contains stewed tomatoes, beef broth, carrots, celery, and a few other ingredients. No one is quite sure where the diet originated, but people use it to lose weight quickly, even though science has shown these types of crash diets are unsafe and typically result in the dieter gaining weight back.

People who have type O blood, for example, are supposed to eat a high-protein diet, while people with type A blood shouldn't eat any meat, according to the diet plan. Depending on your blood type, the diet could severely restrict what you can eat, which could lead to nutrient deficiencies.

A 2013 review of the diet found no proof that it works.

Terry Dubrow catapulted to fame on the TV show "Botched," and he and his wife, Heather, starred in "The Real Housewives of Orange County."

They're leveraging that fame to tout a diet plan that is essentially a version of intermittent fasting, a regimen in which dieters spend up to 16 hours a day fasting, confining their eating to an eight-hour window.

One reason the Dubrow plan may be effective is that it keeps people from mindlessly snacking all day. But fasting also has the potential to increase ketone levels in the body, which can be a problem, especially for Type-1 diabetic patients, who are at risk of developing diabetic ketoacidosis if the body starts running out of insulin.

The couple claim that 100 adults who tried the diet for six months under the Dubrows' supervision lost 33 to 86 pounds. But rapid weight loss doesn't always last, and yo-yo dieting can have serious consequences for your heart.

Gundry has authored two books on dieting, along with a cookbook. His latest, "The Plant Paradox," villainizes plant proteins called lectins, which are in lots of foods, including grains, beans, tomatoes, and potatoes.

Kelly Clarkson loves this eating regimen, but experts in nutrition do not.

"There are some studies on lectins since the 1970s, but they are very inconsistent, and a lot of them are in very isolated environments like in test tubes or animals," Ariana Cucuzza, a dietitian nutritionist at the Cleveland Clinic, told Live Science, adding that translating the results of those studies to humans could "be very confusing" and that "people don't really know how it affects us."

Dieters eat three meals per day and each must consist of 43% protein, 22.5% fat, and 34.5% carbohydrates and are supposed to drink at least four cups of water daily. The Scarsdale diet is meant to be done for one or two weeks straight and says dieters can lose up to 20 pounds during that time.

Losing that amount of weight so quickly is unsafe and can result in weight gain following the diet.

In medieval times, when water was often suspect, people opted to hydrate with ales, and load up their plates with lots of bread and potatoes, often skipping breakfast.

It's not clear if anyone has actually tried to maintain this diet long-term in modern times, but one writer who tried medieval dieting out for a week and a half for Atlas Obscura found she "didn't even get that drunk" and actually enjoyed incorporating more rich broths and stews into her diet, while forgoing sugar.

At the time, a peasant's diet was much healthier than a king's, relying more on plant proteins and nutritious phytochemicals for sustenance instead of subsisting on the rich meats that can prompt gout in high doses.

"The medieval diet was very fresh food," food historian Food historian Caroline Yeldham told the BBC. "There were very few preserves so everything was made fresh and it was low in fat and low in salt and sugar."

Doctors likewise suggest that the grainy, low-nutrient medieval plan isn't totally flawed, as long as you're working out like a peasant and not a king.

Kim Kardashian has attributed the diet to her weight loss in the past. It requires dieters to go through multiple phases, like cutting carbohydrate intake to 20 grams per day during phase one.

That means carbohydrates make up just 10% of a dieter's daily calories, when most nutritional guidelines recommended getting 45% to 65% of your daily calories from carbs, according to the Mayo Clinic. Cutting carbohydrates so quickly and so severely can initially cause fatigue, constipation, headaches, and other adverse side effects.

Atkins ranked 37 out of 41 diets in US News & World Report's annual ranking, largely because the diet's weight loss effects come from it causing a diuretic response, not from instilling healthy and sustainable eating habits.

The keto diet could be considered the OG of fad diets. William Banting, a London funeral director, accidentally discovered his own meaty version of the plan in the 1860s and authored a wildly popular how-to booklet, losing a total of over 50 pounds on his "Banting Diet".

On a well-planned ketogenic diet, people get 70-80% of their daily calories from fat, another 20-25% from protein sources, and consume very few carbohydrates. Keto dieters are thus known for filling up on ketogenic-friendly staples like cauliflower, eggs, cheese, and meat, while avoiding grain-based breads, pastas, and other high-carb foods including apples and carrots.

Ketogenic diets can be also doctor-recommended under the right circumstances; it's a well-established way to help control Type 2 diabetes, and the plan has for nearly 100 years been used to reduce instances of childhood epileptic seizures.

But if people aren't careful about how they approach it, the fatty routine can be disastrous.

Relying too much on protein-packed foods like red meat and cream, while not getting enough essential nutrients from plants can cause dieters to raise up their odds of developing health problems like gout while putting extra stress on the kidneys.

It typically takes around five days for a person's body to enter the ketosis fat-burning state, and this diet shouldn't ever be treated as a quick-fix yo-yo plan for a little extra flab.

"You need to be committed," cancer researcher David Harper, who's been on a keto diet himself for six years, previously told Business Insider.