Popular weight loss diets (fasts, mono diets, the Dukan diet, and others) – are they really healthy?

Popular weight loss diets – are they safe for your health?

People aiming to achieve their desired body weight often get interested in diets that promise quick and spectacular results. This appeals to many who dream of rapid weight loss. But are these dietary approaches really beneficial for health? In reality, their effects may be short-lived, and their long-term impact on the body – harmful.

It’s important to remember that the best method for losing excess weight is to adopt healthy eating habits and incorporate physical activity. Alternative diets can cause adverse health effects. Although they promise fast results, they often lead to weakened immunity, nutrient deficiencies, or metabolic issues.

Examples of weight loss diets

Popular weight loss diets that are not safe for health include:

• detox diets,

• fasting,

• mono diets,

• high-protein diets (e.g. the Dukan diet),

• low-carb diets (e.g. ketogenic diets).

Detox diets

Detox diets are often used as the first stage of a weight loss plan. However, this approach lacks scientific basis.

Every day, your body naturally eliminates metabolic waste through processes involving the liver, kidneys, lungs, and skin. You can support these cleansing processes by following a healthy, balanced diet – there’s no need for restrictive detox regimens, which can be dangerous.

Foods commonly recommended on detox diets (e.g. vegetables, fruits, juices, soups) are beneficial and can be incorporated into your regular diet – but they should not be the sole basis of it.

The promise of fast results draws many people to detox diets. But in practice, they may do more harm than good.

Fasting

Fasting involves temporarily giving up food. Many people believe that fasting has cleansing or alkalizing properties. However, the body already has natural regulatory mechanisms for such processes, making these diets unnecessary.

Fasting and prolonged periods without food can lead to drops in blood sugar levels, which may trigger increased appetite – especially for high-carb and high-fat snacks.

Such extremely low-calorie diets lack essential nutrients, which may pose serious health risks. Although fasting and detox diets can lead to weight loss, the results are usually short-term.

Mono diets

Mono diets are typically based on one or a few ingredients. Examples include the cabbage diet, oatmeal diet, apple diet, or rice diet.

Some versions allow a limited number of other foods, but the overall diet remains highly restrictive and eliminates many valuable nutrients.

Low-calorie diets

Diets that focus on a narrow selection of foods often provide far too few calories and are not tailored to individual needs.

Using a diet with an excessive calorie deficit can cause rapid weight loss – but this is misleading. Why?

• Low-calorie diets reduce glycogen stores, and with them, significant water weight is lost.

• Weight loss is also due to intestinal emptying.

Long-term use of these diets can lead to muscle loss and the yo-yo effect once the diet ends.
Diets with severe calorie restriction and limited food variety can also cause vitamin and mineral deficiencies. These may result in symptoms such as fatigue, poor health, or skin issues.

Although the short-term results may seem satisfying, it’s important to consider the long-term effects.

High-protein diets (the Dukan diet)

The most well-known high-protein diet is the Dukan diet. This approach significantly limits carbohydrate intake (especially from grains) in favor of proteins and fats.

The Dukan diet places emphasis on the selection and preparation of foods. The author recommends primarily eating meat (poultry, veal, and beef), fish and seafood, and dairy products.

This diet should not be recommended for weight loss for several reasons:

• A high-protein diet puts strain on the kidneys and liver.

• Long-term use may result in vitamin and mineral deficiencies.

The Dukan diet lacks foods essential for proper nutrition – such as grains (bread, groats, rice), vegetables, fruits, seeds and nuts, and legumes.

Side effects may include headaches and feeling unwell.

Low-carb diets (keto diet)

Low-carb diets (especially the most restrictive version – the ketogenic diet) continue to be popular.

They are associated with rapid weight loss, improved mood, and reduced hunger. People often report greater satiety while following a ketogenic diet.

The ketogenic diet is characterized by high fat intake (>50% of total energy) and very low carbohydrate intake (5–10% of total energy or <50 g carbs per day).

The aim is to switch the body’s primary energy source from glucose (carbohydrates) to ketone bodies (from fats).

Cutting out carbs automatically limits the range of allowed foods – including sweets – which contributes to weight loss.

However, the ketogenic diet may cause numerous side effects, such as:

• “keto flu” symptoms,

• dehydration,

• loss of appetite,

• serious vitamin and mineral deficiencies.

Long-term use of this diet carries the risk of disturbances in carbohydrate and lipid metabolism. It may also lead to gastrointestinal issues like constipation.

Nutrition organizations recommend the ketogenic diet only for treatment-resistant epilepsy. Some specialists suggest it for Alzheimer’s disease or metabolic syndrome, and some athletes also try it. However, there is no strong evidence supporting its effectiveness in these cases.

A low-carb diet may be considered in specific individual cases but should only be introduced under close supervision by a dietitian or doctor.

People with kidney, liver, or pancreatic diseases should never follow such a diet.
And remember – this is not a lifelong nutritional model.

The most popular weight loss diets – which ones to avoid

The promises made by popular weight loss diets are appealing, but their results are usually short-lived. These approaches are rarely beneficial to long-term health or maintaining a healthy weight.

Some of these diets – such as keto – might be considered under medical supervision in certain cases. However, they are not suitable for everyone.

It’s important to approach popular weight loss diets critically and base your decisions on current scientific knowledge. If you want to lose weight, the best step is to consult a dietitian or use an app like Peater.

With the app, you can set your goal (e.g. weight loss) and choose a diet tailored to your needs. You’ll also have access to a chat with a dietitian whenever you need help. You’ll receive a personalized meal plan to help you shed excess weight – if that’s your goal. But most importantly, you’ll have the confidence that your diet is healthy and balanced.