Five diets with the backing of science

Diets constantly come into and go out of fashion.
Diets constantly come into and go out of fashion. / SUR
  • "A diet may go viral but that doesn't always mean it will work," warns nutritionist Rubén Bravo

Dieting never goes out of fashion. What does fluctuate however, is the popularity of certain diets. In 2018, many varieties went viral, often because they were promoted by famous people or influencers on social media. The Royalty style of diet followed by Megan Markle; the intermittent fasting followed by Hugh Jackman; the 800-calorie diet favoured by Jennifer Aniston; or the vegan diet which Brad Pitt follows, are just some of them. The question is, are they all healthy and do experts recommend them?

Six years ago, the European Medical Institute of Obesity (EMIO) published a ranking of the best and worst of the year's most popular diets. To learn about their benefits and negative aspects, they consulted about 20 experts in obesity including doctors, nutritionists, dietitians, psychologists, naturopaths and surgeons, and analysed genuine cases as well as scientific studies and recognised classifications such as the annual list produced by the British Association of Dietitians and the American publication 'US News & World Report'.

The EMIO ranking was so successful that since then this guide to the best and worst diets according to scientific evidence is now published annually.

"The fact that one type of diet becomes popular doesn't mean that it works or that it is healthy," warns Rubén Bravo, an expert in nutrition and spokesman for EMIO, who says that methods of losing weight healthily always involve a gradual loss -no more than 1.5 kilos a week and six kilos a month - and include all food groups to guarantee that the body functions properly. They restrict amounts of the most calorific foods and help to re-educate nutritional habits.


1.Diet with a high density of nutrients

This wins the gold star for diet of the year. It provides proteins with a high biological value, cardio-healthy fats, vitamins, minerals, antioxidants and quality fibre from foods which make you feel full and are free of empty calories. This is combined with a suitable control over carbohydrate consumption and avoids simple sugars with a high glycaemic index. The main advantage is that, apart from the carbohydrates and sugars, there are no strict restrictions on foods.

"It is a very effective type of diet which we often recommend to patients, because it can be personalised," says Andrea Marqués, an expert on nutrition, dietetics and gastronomy at the EMIO. It is especially recommended for menopausal or post-menopausal women because it helps the body to use the fat deposits as a source of energy, something which is normally difficult at this time of their lives. The main inconvenience is adapting to the restriction of sugars and saturated fats, which can cause anxiety at first.

2. The Royalty-style diet

This is in second place on the ranking. "It is mainly based on eating fruits and vegetables, high quality protein such as free-range chicken, fish such as salmon and tuna, nuts and seeds, while trying to avoid too much gluten," explains Andrea Marqués. It is a type of planning which consists of eating healthily, prioritising certain foods which are beneficial for the health and allowing occasional treats such as a glass of wine, a plate of pasta or something sweet for dessert.

This diet is suitable for any patient as long as they adapt their lifestyle habits to it and take into account possible health problems, because it helps them to lose weight progressively and it can be followed relatively easily over time. This is said to be the diet that Meghan Markle favours.

3. Intermittent fasting diet

Third place goes to this plan which, although it is not new - in some places in the world it has been practised since ancient times for cultural or religious reasons, such as Lent or Ramadan - has recently become more popular. Those who practise it introduce periods of abstinence from solid foods as part of their routine, ranging from several hours to full days. It produces a weight loss of between one kilo and a kilo and a half a week, even if on one day you have eaten a more festive or social meal, because this is compensated by the days or hours of fasting.

It is a diet which can be continued quite easily, or even become a way of life. However, "you do need to be quite disciplined about following the diet and take low-intensity exercise on the days of fasting, such as walking, stretching or yoga," says Carmen Escalada, a clinical nutritionist at EMIO. It is also necessary to eat a balanced diet, because there is no point in fasting if it is alternated with bad nutrition. Celebrities who follow this diet: Beyoncé, Ben Affleck, Hugh Jackman and Nicole Kidman.

4. Scandinavian diet

In fourth place, and supported by the WHO, is this diet which has recently been designated one of the healthiest in the world. It is a version of the Mediterranean diet, which has been developed in northern Europe. The main guidelines are to eat vegetables, pulses, seeds, wholegrains, nuts, fish, seafood, red fruits and canola oil in abundance; eggs, cheese, yoghurt and game in moderation; and red meats only very occasionally. It also avoids added sugars, processed foods, additives and fast food.

"This is more of a healthy form of eating and a lifestyle model than a diet which achieves rapid results," says Carmen Escalada. The plan, which is suitable for everybody, results in a weight loss of between 500g and a kilo a week, and improves parameters such as cholesterol, blood sugar and hypertension. Its main disadvantage is that food shopping will cost more.

Celebrities who follow this diet: Sigrid Agren, Mathilde Goehler and Mini Anden.

5. Controlled vegan diet

This excludes all foods of animal origin: meats, fish, seafood, eggs, dairy products and honey. Those who follow it don't normally do so to lose weight but as a way of helping the environment, but it can also reduce body mass in a healthy way. It has also been shown to improve parameters such as cholesterol, blood pressure and obesity.

"Because this diet imposes numerous restrictions, it is important to follow it with the support and advice of a specialist dietician-nutritionist," says Carmen. The disadvantages are the cost of shopping and the need to take a vitamin B12 supplement.

Celebrities who follow this diet: Alicia Silverstone, Natalie Portman and Brad Pitt.


1. The 800 calorie diet

It is monotonous and lacks nutrients, so it is therefore insufficient to maintain the body of a physically active adult. "It is top of the EMIO ranking for the least-recommended diets due to its popularity among women and teenagers and its versatile and chameleon-like character," explains Estefanía Ramo, a nutritionist at the Institute. You can lose between five and seven kilos a week, but at the cost of numerous risks for health, such as vitamin and mineral deficiencies, low blood pressure and sugar levels, hunger and anxiety. Those who follow this diet burn fewer calories than normal, as the basal metabolism is reduced, and it encourages a rebound effect.

Celebrities who follow this diet: Kylie Minogue, Renée Zellweger and Jennifer Aniston.

2. The diet of detox teas and slimming coffees

This diet consists of consuming slimming teas and coffees with the aim of losing around five kilos in a week. There is a wide range of products high in caffeine or tannin, in the form of capsules or infusions or based on herbs which are said to have other effects associated with weight loss, such as metabolism activators, appetite inhibitors, toxin eliminators, energisers, laxatives or diuretics, anti-cellulites, fat burners etc.

Although it appears to work in the short term, by consuming fewer calories than the body needs, the reduction would be through losing water, never fat, through the dehydration which could occur by having to urinate more during the day. It can have a major rebound effect and pose a risk to health. In the long term, those following this diet could even end up weighing more than they did before.

Celebrities who follow this diet: Kim Kardashian, Demi Lobato and Gwyneth Paltrow.

3. The blood group diet

This originated in the 1980s and is based on the premise that "some foods may be good for some people but toxic for others". Its followers believe that as well as helping to lose weight, it can prevent illnesses.

According to this diet, every blood group benefits from following a diet determined through evolutionary inheritance. So people with blood group O, which is considered the oldest - although that has recently been disproven - should eat a diet high in animal proteins, typical of the hunter-collector. A vegetarian diet is recommended for blood group A, dairy products for group B and a mixture of the diets for group A and group B for those whose blood group is AB. So far, no scientific study has supported this theory, which experts consider "a miracle diet that tries to cheat people and is based on unproven claims," insists nutritionist Sonia Peinado.

Celebrities who follow this diet: Demi Moore, Kate Winslet and Miranda Kerr.

4. Ketogenic diet or keto diet

This was the most searched-for diet on Google in 2018. Its objective is to lose a considerable amount of weight fast, around 12 kilos in a month. It involves reducing carbohydrate consumption. Limiting the consumption of these macro-nutrients can affect the correct functioning of the body and lead to constipation, diarrhea, asthenia and muscle cramps, among other problems. On the other hand the abuse of proteins, its 'star' nutrient, can lead to an increase in uric acid and raise the probabilities of suffering from gout.

It is considered dangerous for people with cardiac illnesses, because a diet high in fat can compromise the functioning of the heart, and it is not advisable for people with liver problems because they have difficulty in metabolising fats.

Celebrities who follow this diet: Halle Barry, Jennifer López, Megan Fox and Adriana Lima.

5. Diet of nutritional supplements with slimming effects

This produces a series of effects associated with weight loss: suppression of appetite, improved digestion, regulation of blood sugar levels and optimises the metabolism. "It is important to underline that this is based on nutritional supplements which do not replace, but complement, certain things in a diet which is supervised by a professional," says Mireia Elías, an expert in dietetics and sports nutrition at the EIMO. It must be accompanied by healthy eating and regular physical exercise.

Celebrities who follow this diet: Princess Eugenie and Prince Harry both used it before their respective weddings.