Kim Kardashian, 42, is no stranger to diet controversy, but her 2022 weight loss for the Met Gala prompted concern from experts who said the “extreme” tactics could be unhealthy. She followed a strict carb-cutting diet to lose 16 pounds (7kg) in three weeks.

Kardashian told Vogue she lost 16 pounds in a matter of weeks by cutting out sugar and carbs, “just the cleanest veggies and protein”. She also said she ran on a treadmill and wore a sauna suit to further shed weight.

But rapid weight loss isn’t sustainable and may not help with fat burning, especially long term, a dietitian told Insider.

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Cardio and carb-cutting may result in weight loss initially, much of which may be water weight, but can often lead to rebound weight gain known as “yo-yo dieting” that may worsen health issues over time.

For healthy weight loss, a goal of about one or two pounds per week is what experts recommend, ideally through making small, achievable changes to lifestyle and daily habits.

2. Rebel Wilson: the Mayr Method

However, in April, despite multiple reports confirming her use of the Mayr Method, Wilson took to social media to deny ever using the diet. “This was never my diet, please stop writing this stuff,” she wrote over a screenshot of a British tabloid’s reporting of her weight loss method.

It’s possible that the news was picked up when Wilson visited Vivamayr clinic in 2019, per People.

The diet is based on the theories an Austrian doctor developed about health 100 years ago. The Mayr Method, named for Dr. Franz Xaver Mayr, is a complex set of habits that has become the basis of treatment at Vivamayr, a chain of luxury wellness and medical spas beloved by celebrities.

But experts say the Mayr Method is a mix of good advice and pseudoscience nonsense.

For instance, the diet emphasises “mindful eating” or slowing down to enjoy the experience of your food, which can be a great way to get in tune with your appetite and avoid overeating. However, the diet’s instruction to chew each bite at least 40 times is excessive, according to dietitians.

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Similarly, the Mayr Method’s principles of cutting out caffeine, sugar and dairy, not snacking between meals or eating raw food after 4pm aren’t science based.

The diet’s so called “high alkaline” foods like fruits and veggies are healthy, but because they’re nutrient-dense, not because they actually balance your pH level, experts have said.

3. Chris Hemsworth and David Harbour: intermittent fasting

Intermittent fasting, or limiting your meals to a specific window of time each day, has become a popular diet to speed weight loss and reduce the risk of chronic illness. Celebrities have picked up the diet to help transform their bodies for specific roles.

“Everyone thinks of him in Thor, being big and muscly, but this was the big accomplishment for me,” Zocchi said. “We implemented intermittent fasting, along with lower calories, and it was crazy how much that worked.”

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“It really did work for me. I don’t know if it’s just code for starvation but it’s basically like … I was hungry a lot of the time,” he told GQ.

The evidence behind intermittent fasting is mixed, despite its popularity. It may help people lose weight by reducing overall calories, but a 2020 study found intermittent fasting may not boost weight loss in every instance, and may be more likely to cause muscle loss.

4. Chris Pratt: the Daniel Diet

Men’s Health reported in 2019 that Chris Pratt, 43, embarked on a fast called the Daniel Diet, which is inspired by the Bible. Daniel Dieters only eat fruits, vegetables and unleavened bread for 21 days straight, with the overall goal of regaining focus on Christ-centred teachings, according to the Daniel Diet website.

Like other restrictive diets, the diet relies on the idea that the body needs to detoxify itself. But a special eating plan isn’t necessary to make this happen.

However, according to the US Department of Health and Human Services (HHS), diets that severely restrict calories or the types of food you eat usually don’t lead to lasting weight loss. Moreover, they may not provide all the nutrients you need.

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5. Shailene Woodley: clay

Known for her roles in Divergent, The Fault in Our Stars and Big Little Lies, Shailene Woodley, 30, has said she swallows a half teaspoon of clay in eight ounces of water each morning for its supposed detoxifying attributes.

“Clay is one of the best things you can put in your body,” she told a beauty blog, Into the Gloss. Woodley allegedly heard about it from a taxi driver and said it “binds to other materials in your body” to help you get rid of “negative isotopes”.

This is a bogus medical claim; your kidneys and liver don’t need help processing toxins. Clay might have trace amounts of some beneficial minerals, like iron and calcium, but there are better ways to obtain them (for instance, by eating foods rich in those minerals like spinach, broccoli, kale and nuts).

6. Miranda Kerr, Jessica Alba and Blake Lively: juice cleanse

Juice cleanses have become synonymous with celebrity diet culture. These cleanses are meant to flush the body of toxins and act as a dietary “reset”, even though they aren’t science-backed weight-loss methods.

Whether the cleanse involves forgoing meals altogether or replacing select meals with juice, the concept of a juice cleanse doesn’t match up with human biology. The body has a built-in detox system that gets rid of toxins sans pricey sugar water.

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“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,” registered dietitian Rachael Hartley said.

Restricting calories so severely could certainly result in weight loss, but at the cost of feeling perpetually tired, hangry (hungry and angry) and being unable to keep the diet up for more than a week’s time. If you tried for longer, you’d likely become nutrient deficient, experts said.

7. Gwyneth Paltrow: goat milk cleanse

“In those days [biblical times], when a healer learned of a worm infestation, they would put the patient in a tub of milk until the worms would come out to drink – parasites love milk!” Lancaster said.

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Not only is this advice lacking evidence, but drinking raw dairy could also lead to foodborne illness – and subsequent hospitalisation.