Very low calorie diets (VLCDs) have emerged as an appropriate option for the treatment of obesity in the patients who have some contraindication to receive pharmacological or surgical treatment. These diets are defined as formulated foods with energy content of between 450 and 800 calories per day, which is the only source of energy and all the essential nutrients required in a weight loss program. The objective of Very low calorie diets (VLCDs) is to induce a rapid weight loss (1.5 to 2.5 kilograms per week), preserving muscle mass, for which a high content of proteins of high biological value is delivered; a minimum of 50 grams of protein and 55 grams of carbohydrates per day must be provided.
What are Very low calorie diets (VLCDs)?
Very low calorie diets are followed in the medical field since 1970 in order to induce rapid weight loss. Most of the recommendations regarding the convenience of their use, if not all, allude to the need to limit them to clinical practice, since it is convenient that the patient is monitored at all times because of the risks involved. The approach to this dietary strategy, especially in cases where its use is prolonged over time.
Low calorie diets or VLCDs are linked to the hospital environment, given the risks involved in monitoring
When are VLCDs used?
In most cases VLCDs are used in the treatment of morbid obesity, with a body mass index higher than 40. Similarly, very low calorie diets are often part of the postoperative treatment of certain interventions. bariatric surgery, especially when they are restrictive. Its short-term effectiveness is contrasted and, in a short period of time, patients confirm rapid weight loss. However, most of the scientific literature attributes to very low calorie diets a low effectiveness in maintaining the weight lost in the medium and long term. In a 2006 review carried out on this topic and published in the Obesity magazine, it is concluded that, although the initial short-term loss of very low-calorie diets is greater than that attributed to diets with a lower energy reduction (the called Low Calorie Diets or LCD), the durability of these losses are not greater. In addition, it is suggested that the use of food substitutes with diets of 1,000 to 1,500 kcal / day is a more effective alternative and less expensive than very low calorie diets, when you want to lose weight.
Most people who manage to maintain the lost weight do not use very restrictive dietary strategies
In 2008, in an article of the same publication, it is affirmed that the large initial weight losses obtained by the individuals who had followed VLCD were not maintained over time, as opposed to what happened to individuals who had resorted to other tools for lose weight based on advice. Most of the people who maintained their weight better after two years were those who chose another system than very low calorie diets.
Mechanism of action
is that by reducing the daily caloric intake to less than 800 calories, lipid metabolism is stimulated as the first energy source and given the high contribution of proteins of high biological value, lean mass can be preserved. On the other hand, the increase in the production of ketones, due to the low intake of carbohydrates induces greater satiety, which manifests itself a few days after the start of the diet.
How they work?
One of the most used ways to achieve a diet with these characteristics is the replacement of meals with liquid protein formulas. These last ones contain proteins of high biological quality and seem to produce greater weight losses, in comparison even to other diets very low in calories. This has been attributed to obese individuals their intake by approximately 40 to 50% (due to the difficulty in estimating portion sizes, macro-nutrient composition, caloric content and meal reminder).
The VLCDs have been used since 1970 to induce rapid weight loss, however, at the beginning of its use serious adverse effects were reported, including deaths associated with its use. This was because the proteins of the first formulas were hydrolyzed collagen, which lacks tryptophan which is an essential amino acid and were deficient in vitamins and minerals. However, since the introduction of formulas with proteins of high biological value (milk, egg, soy), they are considered safe and effective if they are used in well selected obese individuals under medical supervision, and can be used for periods of up to 12 to 16 weeks.
Diets without medical supervision
Despite the warning of their risks, it begins to detect an important use of very low calorie diets away from the clinical setting, so that some people decide to follow this type of treatment without taking into account the risks involved. Sometimes, the opportunity to put them into practice comes from a health professional who provides the nutritional preparations and tells the patient how to administer it, but follows up on an outpatient basis. This dietary option is carried out from meal replacements and not with food as such.
VLCD AND HORMONES, BAD COMBINATION
Sometimes, the interest to lose weight exceeds the reasonable. In the United States, a solution that was proposed more than 50 years ago is becoming increasingly popular. It consists of the administration of human chorionic gonadotropin or hCG and the ambulatory monitoring of diets with a maximum of 500 Kcal / day. In addition, the hCG is provided by medical professionals, along with the necessary syringes so that the interested party can self-administer it in the privacy of their home.
The prescription of hCG is approved in the treatment of infertility and other related uses and, in the United States, doctors can also prescribe it, if necessary, in order to lose weight, although that is not their specific indication. Proponents of this method say that the administration of hCG in someone who is not pregnant has the effect of making the body believe that it is and, in this way, fat burns more quickly, while maintaining or even promotes the growth of muscle mass.
However, as early as 1995, a review study published in the British Journal of Clinical Pharmacology resolved the question of whether or not the diet with hCG actually worked. For this, it carried out the analysis of 14 randomized clinical trials. Of these, only two found that people who received hCG lost more weight and felt less hungry than the rest of individuals with the same 500-calorie diet, who had received a placebo in the form of saline injections. In addition, in one of these two studies (compared to the other 12 who found no difference in weight loss with the use of hCG versus placebo), the main author had clear conflicts of interest.
In response to the questions raised by the popularity of this “diet”, the United States Food and Drug Administration (FDA) has had to reiterate a warning that it made for the first time in the mid-1970s and that obliges that in the hCG packaging it is compulsorily stated that: “It has not been shown that (hCG) increases weight loss, makes the distribution of body fat more ‘attractive’ or reduces hunger and discomfort low-calorie diets. ” In addition, warns that its use can lead to serious side effects: increased risk of blood clots, depression, headaches and increased sensitivity and breast size.
They can only be used for a limited time (up to 12 to 16 weeks), since the adherence decreases with time and the possible adverse effects associated with prolonged use.
However, it is important to mention that these diets have limitations in their use, and are only safe if they are indicated and supervised by professionals with knowledge of the psychological aspects that cause a rapid weight loss. They should be indicated in selected patients, its use being contraindicated in patients with renal and hepatic diseases, cardiac arrhythmias, type 1 diabetes, psychiatric illnesses or eating disorders, breastfeeding, pregnancy, children and the elderly.
In conclusion, VLCDs are effective and safe in only short period of intervention
- OMS. Obesity: Preventing and managing the global epidemic. Report of a WHO consultation. Ginebra, OMS, 1998.
- James WP. The epidemiology of obesity: the size of the problem. J Intern Med 2008; 263(4): 336-52.
- Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults – The Evidence Report. Obes Res 1998; 6 Suppl 2: 51S-209S.