[Definitions and epidemiology of childhood obesity V. Nègre]

DEFINITIONS AND EPIDEMIOLOGY OF CHILDHOOD OBESITY. Childhood overweight and obesity are defined using the curves established by the International Obesity Task Force (IOTF). A child is overweight when his BMI is above the IOTF 25 curve (corresponding to a Body Mass Index [BMI] of 25 at the age of 18). He is obese when his BMI is above the IOTF 30 threshold. However, in clinical practice, it is more important to appreciate the evolution of the curve than the level of corpulence itself, as this helps to orientate the diagnosis and better understand the mechanisms of excessive weight gain. Currently, even if a stabilization of the prevalence seems to have been observed between the years 2000 and 2015 in developed countries, this is not the case in the lower income countries. In France, 18% of children are overweight, of which 3 to 4% are obese, with a very marked social gradient. Since 2015, there has been a trend towards a re-increase in severe forms of obesity, particularly among girls and children from families with the greatest socio-economic difficulties. The initial confinement imposed by the Covid-19 pandemic seems to have aggravated this trend.