Following feedback from stakeholders on the report of its expert committee, ANSES has published an opinion on weight-loss diets

Following a consultation phase, ANSES has published its Opinion on weight-loss diets

On 25 November 2010, ANSES published an expert report on the risks related to dietary weight-loss practices. Given the importance, complexity and sensitivity of the issue, the Agency wished to submit The report to members of the scientific and medical communities, representatives of associations and managers of professional organisations in order to be able to take into account any additional scientific information before drafting its Opinion.

Approximately ten contributions were received. These came mainly from scientific societies and study groups (the National Federation of Medical Nutrition Associations, the Ethics and Health Group [Group Ethique et Santé], study groups on obesity and overweight), consumer associations (Famille de France), diet promoters and professional guilds.

In the light of these contributions, ANSES has now issued its Opinion, which expresses its final conclusions and makes recommendations. In addition to the Opinion, the Agency has also published the contributions received as well as its own clarifications in response to the remarks made by stakeholders.

Weight-loss diets are not without risk

The Agency's Opinion reaffirms the conclusions of its report, namely that following diets for the purpose of slimming is not without risk, especially for vulnerable population groups (adolescents, pregnant women, the elderly, etc). The risk of more or less serious health effects should not be neglected.

This collective expert appraisal in fact revealed, after a review of the scientific literature, that the weight-loss diets widely promoted in stores and on the Internet can involve clinical, biological, behavioural and psychological risks when they are undertaken without consulting a specialist or without follow-up supervision.

An analysis of the scientific data also confirmed that following diets can cause profound changes to the body's energy metabolism. Such modifications are often the cause of a vicious circle including the regaining of weight - often more than initially - in the medium- or long term. Therefore, one of the major, recurring consequences of depriving oneself of food or excluding certain foods, irrespective of the diet involved, is paradoxically, that individuals often regain the weight lost or even become increasingly overweight: the more one diets, the more one is likely to become overweight, particularly if there is a lack of physical activity, which is essential for stabilising body weight.

The main conclusion of The report (PDF) is that the attempt to lose weight by dieting can only be justified from a medical point of view if the patient is actually suffering from overweight (1) and that such diets should be supervised by specialists - doctors specialising in nutrition, dietitians - who are best qualified to recommend a diet suitable for each individual. ANSES would like to remind the public that, as far as health is concerned, there is no substitute for a well-balanced, varied diet, while ensuring that the daily caloric intake does not exceed the body's needs. Furthermore, in order to reduce the risk of gaining weight, any change in eating habits must be combined with regular physical activity.

The background to The report (PDF)

Overweight and obesity, which affect respectively 32% and 15% of French people over 18 years of age, are a pressing public health problem requiring treatment by a health professional and which may justify following a diet under medical supervision. However, in many cases, weight-loss diets are adopted simply for aesthetic reasons, even though the individual on the diet is not overweight and has no medical reasons for doing so.

ANSES was therefore asked by the Ministry of Health to assess the risks involved in such practices. The assessment was conducted within the framework of the overall "body-image" issue, as part of the National Health and Nutrition Programme (PNNS2: 2006-2010). This report (PDF) concludes the collective expertise process undertaken by a working group made up of scientists and nutrition experts. The work, validated by the ANSES expert committee on human nutrition, was based on a review of French and international scientific literature and on hearings.

(1) The International classification defines obesity in women and in men up to the age of 65 years as a BMI (body mass index) equal to or greater than 30 kg/m2.