An endless stream of diets promises to improve health and shift the balance.
But taking it apart, which will actually make you slimmer without harming your long-term health, can seem nearly impossible.
Here, MailOnline asks two leading dietitians which regimens are actually best for maintaining a healthy lifestyle…
The keto diet involves cutting out most carbohydrates and adding a large amount of fat, keeping your blood sugar levels at a safe but low level, which encourages the body to burn fat for energy, which is known as ketosis.
Keto
It’s a regimen praised by A-list celebrities including Kim and Kourtney Kardashian, Halle Berry and Gwyneth Paltrow.
The ketogenic diet, also known as the keto diet, involves cutting out almost all carbohydrates and adding a large amount of fat and protein to each meal.
As a result, bread, rice and pasta are completely excluded, as are sweets, chocolate and pastries. Even dairy, fruits and vegetables are limited.
It has been shown to aid weight loss and lower blood sugar levels in type 2 diabetics. according to Dr. Duane Mellor, a dietitian at Aston University in Birmingham.
“It has the advantages of being low in sugar and filling thanks to the proteins,” he said.
The diet aims to force the body to burn fat for energy instead of glucose – a process known as ketosis.
This fat-burning effect of the diet is why it is marketed as good for weight loss, says Rob Hobson, registered nutritionist and author of Unprocess Your Life.
Plus, the high fat content can reduce appetite and promote weight loss, he says.
However, the diet – similar to Atkins and Dukan’s approaches – is notoriously difficult to maintain. Followers need less than about 40 grams of carbohydrates and 75 grams of protein per day for ketosis to occur.
Furthermore, cutting back on plant-based foods could lead to nutritional deficiencies, Mr Hobson warns.
“The initial phase of this diet also brings unwanted symptoms such as headaches, fatigue and irritability,” he said. ‘The low fiber content of this diet may affect digestion.’
Dr. Mellor warns that the high-fat diet could theoretically increase the risk of cardiovascular disease.
However, this can be offset if those who follow the diet successfully lose weight, as this reduces the chance of developing the condition, he says.
Carnivore
It will come as no surprise that dietitians are not fond of a diet that only eats meat, eggs and cheese and no fruit or vegetables.
The incredibly restrictive approach known as the carnivore diet stems from the belief that our ancestors ate mainly meat and that today’s diets, which are typically high in carbohydrates, increase the risk of health problems.
It has been promoted online by commentator Jordan Peterson and Shawn Baker, an American orthopedic doctor who believes the diet can help treat anxiety, obesity, diabetes and even arthritis.
The carnivore diet is a version of the Keto diet because without carbohydrates the body will burn fat.
Benefits of a high-protein diet include feeling full longer because the nutrient takes longer to digest than carbohydrates.
However, Dietitians do not recommend the carnivore approach.
‘This diet eliminates plant foods and limits it to animal foods only, so it is restrictive,’ Mr Hobson said. ‘It’s not a diet I would recommend.
‘The high protein content can help with feelings of satiety and increase feelings of fullness, and it is clear that protein has many roles in the body.
‘I think there is an opportunity to lose weight, given the likelihood that you would eat fewer calories. But this will probably be short-lived.’
Because the diet excludes all fruits, vegetables, grains and legumes, the body will be deficient in essential sources of fiber, vitamins and minerals, explains Mr Hobson.
Adults should eat 30 grams of fiber a day to lower the risk of heart disease, stroke and type 2 diabetes, the NHS says.
The restrictive carnivore diet is promoted online by the likes of Jordan Peterson and Shawn Baker, an American orthopedic doctor, who believes the diet can help treat anxiety, obesity, diabetes and arthritis
Not only is it bad for gut health, but if followers eat processed meat in excessive amounts they can also increase their risk of cancer, warns Dr Mellor.
Health chiefs recommend eating no more than 70 grams of sausage, bacon or ham a day to reduce the risk of bowel cancer.
Like the keto diet, the carnivore diet may be impossible to maintain in the long term, says Mr Hobson.
“Consuming large amounts of meat and dairy products can lead to eating large amounts of saturated fat, which can increase cholesterol levels and other risk factors for heart disease,” he said.
‘Then there are the practical aspects of maintaining this diet, which can be difficult in social circumstances.’
Vegan
It’s one of the biggest health trends of the past decade and is hailed as one of the best diets.
Veganism means cutting out all meat, dairy and eggs and eating plenty of fruits, vegetables, whole grains, legumes, nuts and seeds.
Advocates say they can get all the nutrients they need by eating fortified foods and supplements to get enough calcium, iron and vitamin B12, which are difficult to get in large enough amounts while being plant-based.
‘Vegan diets can be healthy for both us and the planet, they can be nutrient-rich and packed with fibre, vitamins and minerals,’ says Dr Mellor.
‘The downside is that it takes a little more planning to be healthy, as it may lack nutrients such as vitamin B12, vitamin D, iron and iodine, which need to be taken in to ensure a vegan diet is balanced and healthy.
‘Even if you want to eat vegan, it is important to mix protein sources so that you get the full range of amino acids they contain.’
According to the NHS, the Mediterranean has been linked to reducing the risk of heart disease, some cancers, type 2 diabetes and even dementia.
Mr Hobson says the high fiber diet is not only good for your gut, but has also been linked to a reduced risk of heart disease, type 2 diabetes and some cancers.
However, he warns that the rise of vegan chocolate, fast food and meat alternatives means there is ‘many more opportunities for vegans to be less healthy’.
These options are ultra-processed and high in salt, sugar and fat, he says.
Mediterranean
Instead of eating pasta and pizza, the Mediterranean diet includes an abundance of fresh fruits, vegetables and healthy brain foods like fish and olive oil.
It has long been hailed as the secret behind why Italians and Spaniards live long, healthy lives and have low rates of obesity and diet-related diseases.
It has been linked to a reduced risk of heart disease, some cancers and type 2 diabetes.
That is why it is one of the most recommended medications by dietitians.
Mr Hobson even goes so far as to say it is the ‘perfect diet’, with research showing it is a ‘gold standard way of eating’.
He adds that it includes a wide variety of foods and that the diet also accommodates a plant-based way of eating.
‘I would be most inclined to recommend a Mediterranean diet as the scientific evidence for this approach is the strongest,’ said Dr Mellor.
But he warns against eating too much pasta, bread and risotto and opting for grains and barley instead.
He said: ‘A traditional Mediterranean diet is based on available fresh and minimally processed foods. If we try to follow this, we might opt for the less healthy versions with added fat, salt and sugar.
‘For example, adding a garlic bread to your lasagna.
‘I would encourage people to think about simple dishes made from plants, such as salads and vegetables, and adapt these to foods that are locally available, such as eating pearl barley instead of risotto rice.’