In a nutshell, the alkaline diet promotes the intake of ‘alkaline’ foods, such as fruit, vegetables, legumes and nuts, and the reduction of ‘acidic’ foods, such as meat, eggs and alcohol, with the aim being to change the body’s PH levels.

“It encourages fruit and vegetable consumption and limits processed foods, but the body regulates pH independently, so the diet's premise is flawed,” says Eli Brecher, a registered associate nutritionist (ANutr) specialising in gut health and host of The Gut 360 podcast. “And, it may lead to unnecessary food restrictions and nutritional imbalances.”

“The fundamental premise that food can significantly change your blood pH is not scientifically supported. Your body naturally maintains pH balance regardless of diet,” agrees qualified nutritional therapist and author Rosie Millen (@missnutritionist).

Not a diet that promotes much variety, the cabbage soup diet consists of eating cabbage soup for a week alongside select additions, such as fruit and milk. Supporters claim to be able to lose up to 10 pounds in just seven days while following it, but these claims are unsubstantiated.

Cabbage is certainly nutritious – it's packed with vitamin C, fibre and antioxidants that support the immune system and digestive health,” explains Rosie. “The diet can lead to fast initial weight loss, but it’s primarily water weight being lost, rather than sustainable fat loss.”

Nor is the weight loss sustained, says Rosie: “It’s far too restrictive to be sustainable or healthy. It deprives your body of the essential nutrients, proteins and healthy fats needed to function properly, and this extreme calorie restriction can lead to muscle loss, metabolism slow down and nutritional deficiencies. Plus, once you return to normal eating, the weight typically returns quickly, creating that frustrating yo-yo effect.”

Also known as human chorionic gonadotropin, HCG is a protein-based hormone produced by the body during pregnancy. It also happens to be the hormone that determines a positive or negative pregnancy test. But, rather than needing to fall pregnant to experience its full benefits, the HCG diet recommends taking hormone injections alongside a reduced calorie intake of approximately 500 calories a day in order to experience its purported weight loss benefits (which can apparently be up to two pounds a day.)

I struggle to find legitimate pros to the HCG diet,” warns Rosie. “While people do lose weight following it, this is due to the extreme calorie restriction (often 500-800 calories daily), rather than any special effect of the HCG hormone. The severe calorie restriction is simply unsafe and unsustainable. It can lead to muscle loss, nutritional deficiencies, gallstones and metabolic damage. The HCG hormone injections or supplements have not been proven effective for weight loss and aren't approved by regulatory authorities for this purpose, either.”

Given Beyoncé is said to have followed a variation of the so-called "Master Cleanse" – which involves drinking a concoction of lemon juice, maple syrup, cayenne pepper and water – it’s hardly surprising that many eager to shed some pounds have looked to follow in her footsteps. “While it may lead to rapid short-term weight loss due to extreme calorie restriction,” says Eli, “it deprives the body of essential nutrients. It can also cause muscle loss, fatigue and dizziness, and may slow metabolism, making long-term weight management harder.”

If you regularly find yourself reaching for the sweet stuff come the post-afternoon slump, you may be tempted to cut out sugar altogether – especially if there are added slimming benefits, too. “Reducing added sugar has legitimate health benefits,” explains Rosie. “It can help stabilise blood sugar levels, reduce inflammation, improve dental health and decrease the risk of chronic diseases like heart disease and type-2 diabetes.”

However,problems can arise when "zero sugar" is taken to the extreme, such as eliminating naturally occurring sugars in fruits, vegetables and dairy. “These foods contain essential nutrients, fibre and antioxidants that are crucial for overall health. Some very strict no-sugar approaches can lead to nutrient deficiencies and an unsustainable, restrictive relationship with food. The key is balance, not complete elimination.”

This eating plan has become popular in part due to the idea that it’s a ‘natural’ way of eating. Also known as the Caveman Diet, it recommends excluding fruit, vegetables, grains, nuts, seeds and legumes in favour of meat, eggs, seafood and select dairy products.While there are undoubtedly benefits to the diet – such as high protein and fat consumption, which can promote satiety, and a reduced intake of processed foods – the diet lacks the fibre, vitamins and antioxidants found in plant foods, and may increase the risk of digestive issues, heart disease and nutrient deficiencies, says Eli.

It’s easy to see why a celery juice diet may appeal – after all, who doesn’t feel pious after downing a vibrant energy-boosting juice in the morning? But, while juices are a fantastic way of boosting your fruit and veg consumption, drinking 475ml every morning – as recommended by supporters of the diet – is more extreme.

“Celery does have some nutritional benefits,” says Rosie. “It's hydrating and low in calories, and contains vitamins K and C, plus potassium and antioxidants. However, despite claims made on social media, celery juice is not the miracle cure it's often portrayed to be – there's limited scientific evidence to support many of the claimed benefits. Plus, relying primarily on celery juice means you’re missing out on essential nutrients, proteins and healthy fats. Juicing also removes any beneficial fibre from the celery.”

The aim of the Whole30 – where foods such as grains, dairy and sugar are eliminated for 30 days before being introduced again – is to identify allergens and sensitivities, but many also follow it in the hopes of shedding some pounds. But, what do nutritionists have to say about it, and is it as 'whole' as it purports to be?

“Whole30 does have some noteworthy benefits,” says Rosie. “It encourages eating whole, unprocessed foods and eliminates common inflammatory foods such as sugar, dairy, grains and alcohol. Many people report improved energy levels, better sleep, clearer skin and reduced bloating.”

However, while not necessarily labelling it as "bad", the Whole30 diet can be restrictive and socially isolating, says Rosie. “The all-or-nothing approach doesn't teach sustainable moderation skills, and the rigid rules can foster an unhealthy relationship with food. Nutritionally, the diet also restricts healthy food groups such as legumes and whole grains, which provide essential nutrients and fibre.”

If fad diets aren’t the magic key to weight loss, what do nutritionists recommend as a long-term and sustainable solution? It all comes down to having a balanced diet that's “rich in whole foods, lean proteins, healthy fats and fibre,” combined with sustainable lifestyle changes, such as regular exercise and mindful eating, recommends Eli.

Rosie also cites hydration, quality sleep, stress management and consistency as being key. “The truth is, none of these fad diets teach us sustainable habits,” she says. “I've always found my clients achieve the best long-term results when they focus on building a balanced, nutrient-dense diet that works with their lifestyle, rather than against it.”

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