24/11/2010 3 min

Weight-loss diets: risky practices

The French Agency for Food, Environmental and Occupational Health & Safety (ANSES) today published an expert report on the assessment of risks related to dietary weight-loss practices. The pursuit of slimness and the proliferation of diets that can be followed alone without medical supervision have prompted the authorities to question the risks related to these practices. This report will be submitted to stakeholders for consultation, in order to draw up some recommendations in an opinion to be published in early 2011.

Overweight and obesity, which affect respectively 32% and 15% of people over 18 in France, are a real public health problem requiring treatment by a health professional and in some cases justifying the prescription of a diet under medical supervision. However, dietary weight-loss practices are often adopted, in the absence of overweight or any medical indication, essentially for aesthetic reasons.

The Ministry of Health therefore requested that ANSES assess the risks arising from these practices. The assessment made falls within the scope of the "body image" topic organised by the French National Health and Nutrition Programme (PNNS 2: 2006-2010).

Today's report is the result of a collective expertise process undertaken by a working group made up of scientists and nutrition experts. The work, which was validated by ANSES' Expert Committee on Human Nutrition, was based on a review of the national and international scientific literature, and on hearings.

The expert assessment shows that slimming diets, widely available to the public in stores and via the Internet, and followed without specialist recommendation or supervision, can pose risks of varying severity to health. It highlights the adverse effects on the body, including the bones, heart and kidneys, as well as psychological disturbances including behavioural eating disorders.
Analysis of the scientific data also established that following diets may cause profound changes to the body's energy metabolism. Such changes often then trigger a vicious cycle of weight regain in the more or less long term, and which may be exacerbated.
A major and recurrent consequence of the corresponding dietary deprivations and exclusions, irrespective of the diet followed, is thus paradoxically weight regain or even overweight: the more diets are followed, the more weight regain is facilitated, even more so in the absence of physical activity, which is a crucial factor in stabilising weight.

The main conclusion of this report is that seeking weight loss by dietary means can only be justified medically in the case of actual overweight(1), and that this process must be supervised by specialists - doctors specialising in nutrition, dieticians - capable of recommending the diet best suited to each individual's specific needs. ANSES also stresses that in terms of health, nothing can replace eating a well-balanced and varied diet, and ensuring that daily caloric intakes do not exceed requirements. Furthermore, to reduce the risk of weight gain, changes in eating habits must be accompanied by regular physical activity.

Considering the importance, complexity and sensitivity of this subject, ANSES hopes to enrich the consultation undertaken, by bringing this report to the attention of members of the scientific and medical community, representatives of associations and leaders of professional organisations.

The consultation will continue until 15 January 2011. All information received will be made public and will undergo a detailed analysis by the Agency while it draws up its recommendations.

(1)The international classification defines obesity in women and in men up to the age of 65 according to a BMI (Body Mass Index) equal to or greater than 30 kg/m2.