Every so often new diets appear, each one promising the same thing: rapid weight loss without effort. These so-called miracle diets impose very severe calorie restrictions, and usually lead to deficiencies that make them both impossible to sustain in the long term and dangerous to people’s health.
New weight-loss diets appear on the market regularly.Advertised on television programmes and in fashion and food magazines,they all have one thing in common:the promise of rapid weight loss with little or no effort on the part of the dieter.These so-called miracle diets are,in many cases,borne more out of the desire to make a profit than to promote healthy and balanced eating.They impose very severe calorie restrictions – which generally cause mineral and vitamin deficiencies and metabolic changes – and are often monotonous,which make them unsustainable in the long term and dangerous to people’s health.
Prescribed by people outside of the field of nutrition,these diets are characterised by the small amount of calories that they provide.When in this state of semi-fasting,the body reacts by compensating for the loss of energy by increasing the breakdown of body proteins as an alternative source of energy.This results in the loss of muscle mass and in the formation of ketone bodies,which are dangerous to an organism if they are produced over a long period of time.
However,people who follow these diets associate the loss of muscle mass with the success of their chosen diet,as they often see spectacular results on the scales in the first few weeks.This is due to the fact that muscle tissue is rich in water and loses large quantities of liquid in the first phase of the diet (occasionally assisted by the consumption of diuretics),causing the dramatic weight loss.
An additional problem with these “miracle diets” is that when they come to an end they result in the rapid regaining of the weight lost (the rebound effect),leading to the so-called yo-yo phenomenon,which is associated with increased risk.This tendency to regain weight is exacerbated by the fact that these semi-fasting situations trigger powerful neuroendocrine mechanisms that fight against weight loss.These mechanisms include increased metabolic efficiency,energy saving and an increase in appetite.This causes the weight lost to be put back on rapidly as soon as the dieter starts to eat “normally” again; in addition,this regained weight is predominantly stored as fatty tissue.
To summarise,very restrictive diets that are very low in calories,despite the weight loss they may achieve in the short term,constitute an unacceptable health risk as they can:
- Aggravate a person’s metabolic risk.
- Cause protein malnutrition and vitamin and mineral deficiencies.
- Lead to eating disorders (anorexia and bulimia),which are sometimes more dangerous than the excess weight that is trying to be lost.
- Produce negative psychological effects.
- Encourage the rebound effect.
Generally,so-called miracle diets can be grouped into three main categories:
a) Hypocaloric and unbalanced diets:these include the Mayo Clinic diet,the “Half” Diet,the Gourmet Diet and the Zero Diet.These diets cause a rebound effect which translates into an increase in fatty tissue and a decrease in muscle mass.They also cause the metabolism to adapt to the drastic loss of energy intake,essentially by reducing energy expenditure.Aside from generally being monotonous,these diets also result in numerous nutrient deficiencies,especially if they are kept up over a prolonged period of time.
b) Dissociative diets:the Hay or Dissociated Diet,the Shelton Diet,the Hollywood Diet,the Montignac Diet,the Antidiet,etc.These diets are based on the principle that individual foods do not contribute to weight gain in and of themselves,only when they are eaten in specific combinations.These diets don’t limit the amount of energy-giving foods ingested,but aim to prevent their use as energy substrates by dissociating them.
c) Exclusion diets:these are based on eliminating a particular nutrient from the diet.They may be:
i) rich in carbohydrates but exclude lipids and proteins:the Dr Prittikin Diet and the Dr Haas Diet.
ii) rich in protein but exclude carbohydrates:the Scarsdale Diet,the Astronaut Diet,the Hollywood Diet and the Liquid Protein Diet.These cause highly significant renal and hepatic overload.
iii) rich in fats:the Atkins Diet,the Lutz Diet.These are known as ketogenic diets.They can prove very dangerous to a person’s health,causing serious changes to the metabolism (acidosis,ketosis,increase in blood cholesterol,etc.)