Weight loss, when needed, can be addressed, among other measures, by means of a diet. There are many diets whose object is to lose weight, generally, in the least possible time. But not all diets are suitable for this purpose, nor are all diets based on science. If a diet is to be effective and not pose a health risk, it must meet certain requirements.

• First, one should seek gradual, progressive and moderate weight loss. In order to achieve this without suffering any nutritional deficiencies, it is generally necessary to consume between 20 to 25 calories per kilogram of real weight.
• For example, a woman weighing 80 kg would need about 1,600 to 1,800 calories, depending on the amount of exercise she does. If you eat less, you may suffer from protein, vitamin and mineral deficiencies that may eventually lead to medical problems and, once again, putting on any weight lost. This last aspect is very common because excessively low calorie diets lead to a loss of muscle protein and reduce the metabolic rate to such a point that a rebound effect is triggered.
• The balanced supply of nutrients is very important to lose weight in a health manner and, therefore, the different nutrients must be shared among different food groups.
  • A certain amount of carbohydrates is required per day for the nervous system (brain, nerves), the heart and blood cells (red cells, white cells and platelets) to function correctly. Approximately 40 to 50% of the calories in a diet should be provided by carbohydrates. Carbohydrates are found in food groups that should always be consumed, such as:
  • Cereals (wheat, oats, rye, barley...) and related products (pasta, bread, breakfast cereals...).
  • Rice.
  • Tubers (potato).
  • Legumes.
  • Greens, vegetables and fruit also contain small quantities of carbohydrates.

Sugary drinks and other sweets also contain carbohydrates (sugar), but are not recommended for weight loss diets.

• Between 10 and 20% of the calories in the diet must be provided by protein. Protein-rich foods include meat, fish, eggs, cheese and nuts.
  • 30-35% will come from fat. This latter nutrient is the one that should be restricted most although many unscientific or little proven diets state otherwise.

It is very important to maintain this balanced distribution of nutrients from different food groups. Consequently, there should be a wide variety of foods in a diet aimed at weight loss.

However, many diets advocated as "miracle diets" are based on only one food type for a week (grapefruit, apricot... diet) or for a given period of time or on the restriction or entire food groups, such as diets without carbohydrates or diets based entirely on protein, for example, or high fat diets, which are those where you can eat unlimited amounts of bacon and foods rich in protein and fats, such as cheese, meat, fatty fish...

The drawbacks of these diets are, as mentioned above, the unbalanced and insufficient intake of nutrients, which eventually leads to effects that are very similar to overly restrictive diets. As we need a certain amount of carbohydrates per day, if these are not included in our diet, we will destroy our muscle mass to generate glucose to feed the cells of out central nervous system, red cells...

On the other hand, a diet that is extremely rich in fat may cause an increase in ketone bodies (acetone) in the blood, which leads to dehydration and other metabolic disorders that in some extreme cases have led to sudden death from arrhythmia; more so if you have any previous cardiovascular risk factor, which is often the case of people suffering from obesity.

In other cases, diets that are extremely rich in fat, that limit the amount of hydrocarbon foods, vegetables and fruit may lead to increased cholesterol and triglycerides in the blood.

More information:

- Legislation

- Total Diet Study

Miracle Diets

Miracle diets: a health risk

Glossary of miracle diet terms

 Press releases:

- Weight loss diets and products

- The AESAN website on miracle diets has already been visited by over 87,300 people

- Over 22,500 people have accessed the Spanish Food Safety and Nutrition Agency website that reports on the dangers of "miracle diets"

- Scientific societies as well as associations of doctors and pharmacists are working with the Health Department to inform citizens about the dangers of "miracle diets”

- Are you trying to lose weight? Check whether your diet is correct or whether it is endangering your health