Prevalence of childhood obesity levels off in France

May 15 2008

France may be the first country in the EU to see signs of a levelling off in the national prevalence of childhood obesity, according to the results of two new surveys.

Although the studies show the prevalence of overweight was holding steady, the problem remained worse among the poorest children, where researchers found obesity rates were up to three times higher comparing the lowest socioeconomic group to the highest.

The research, unveiled at the European Congress on Obesity in Geneva, does not explain why the prevalence may be levelling off, but the change comes after the introduction in 2001 of a National Nutrition and Health Programme that includes a comprehensive package of obesity-fighting public health initiatives.

The prevalence of childhood obesity in France is among the lowest in Europe, but as in other countries, it has been increasing in recent years. Overweight rates have been rising faster in children than in adults for the last three decades in France.

Dr Katia Castetbon, head of the Nutritional Epidemiology and Surveillance Unit at the French National Institute for Health Surveillance, said: "The convergence of several studies is encouraging. Public health policy has changed a lot in France since 2000, but we cannot prove that the stabilization is due to these interventions. There has been an increased awareness of the issue of obesity in children and it's possible that this general awareness has had some impact."

Castetbon and her group compared the prevalence of overweight and obesity among 7-9 year olds in 2000 and 2007. In both years, the researchers investigated two random classes from one primary school that was randomly selected in districts across the country. The children were weighed and measured, and their parents completed lifestyle questionnaires.

In the school zones covered in both surveys, the researchers found that 18.1% of the 1,582 children studied in 2000 were overweight, including 3.8% who were obese, and that 15.8% of the 1,014 children studied in 2007 were overweight, including 3.0% who were obese. However, the difference between the percentages in 2000 and 2007 was not statistically meaningful, which means the prevalence is not considered to have changed.

The second study was led by Sandrine Lioret, an epidemiologist in the French Food Safety Agency's Dietary Survey Unit. In 2006-2007, her group conducted a nationally representative survey (INCA-2) of 1,455 children ranging in age from 3 to 17 years old. Height and weight were measured, food consumption was recorded in a 7-day diary and exercise patterns and socioeconomic status were determined by questionnaires. The results were compared with those from a similar survey conducted in 1998-1999 (INCA-1) on 1,127 children in the same age range. The periodic monitoring at the population level of both overweight and its main determinants through the INCA surveys is part of the French national policy to explore the trends in overweight prevalence and its associated risk factors.

The children were divided into three age groups. The prevalence of overweight or obesity among 3-10 year olds was 16.9% in the earlier survey and 14.1% in the later survey. Among 11-14 year olds, the prevalence was 11.7% in the first survey and 15.3% in the second survey; among 15-17 year olds, the prevalence was 14.3% in the earlier investigation and 11.9% in the later survey. As in Castetbon's study, there was no statistically meaningful difference in the percentages between the two surveys in any of the age categories, which means the prevalence did not change.

However, in both studies, there were marked differences between socioeconomic groups, and children from lower socioeconomic backgrounds fared worse.

"In both surveys in our study, rates of overweight were between 2.5 and 3 times higher in children from the lowest socioeconomic level than in those from the highest level, in which parents worked in executive, top management or professional jobs," Lioret said.

Castetbon's findings were similar. "Behind the stabilization there are worrying discrepancies between socioeconomic groups, with lower prevalence being seen among children with executive mothers or fathers than in children from lower socioeconomic backgrounds," she said. "That indicates that more work needs to be done to adapt the approaches to address the needs of these children so that the gap can be narrowed."

Lioret added that it is not clear why children from poorer backgrounds fared worse and that further research is needed to asses which lifestyle factors influence the relationship between socio-economic status and overweight in children. Additional research is also required, she said, to determine whether a low socioeconomic status might be an indirect indicator of other early life factors that influence obesity, such as poor nutrition during pregnancy or breastfeeding patterns.

Professor Jean-Michel Oppert, President-elect of the European Association for the Study of Obesity, who was not part of either study, commented that the early results still showed that obesity was having a major impact on poorer communities, leaving no room for complacency.

"It remains to be seen whether this observed stabilization will last. It's only the first suggestion that it could be levelling off. And the fact that both of these studies found differences between the socioeconomic groups shows the importance of the need to identify the most at-risk groups and develop approaches that are oriented to them," said Prof. Oppert, professor of nutrition at Pitié-Salpêtrière Medical School, University of Paris.

France has been a leader in Europe in introducing public health measures aimed at reducing childhood obesity, including banning vending machines in schools since 2005.

* New data has also been published recently from the Étude nationale nutrition santé (ENNS 2006) which examined for children in similar age groups and found an overall overweight and obesity prevalence of 17.8%, with an overweight and obesity prevalence of 25.3% in boys and 16.5% in girls aged 11-14 years and 16.7% for boys and 16.5% for girls in the 15-17 year age group.