Underweight and overweight among children and adolescents in Tuscany (Italy). Prevalence and short-term trends

Introduction. The recent increase in both childhood obesity and adolescent anorexia nervosa in developed countries has underlined the important consequences that these trends may have on public health, as there is an increased risk that these conditions may become chronic diseases in adulthood. Therefore, it is necessary to monitor prevalence rates and trends in thinness and overweight (including obesity) among children and adolescents at different levels: international, national and sub-national. Since 2001/2002, a nutritional surveillance system has been implemented in the Tuscany Region to estimate the nutritional status and lifestyles of children and adolescents. The main objectives were to assess the prevalence of thinness, overweight and obesity among Tuscan children and adolescents and to provide baseline information on the prevalence of thinness, for the first time calculated according to the new international definitions, for geographical comparisons and descriptions of time trends. Methods. Independent cross-sectional sample surveys were conducted in 2002, 2004 and 2006 in Tuscany, North-Central Italy. Data were collected from stratified two-stage cluster samples of children aged 9 years (n = 3,048 in 2002 and n = 1,430 in 2006) and of adolescents aged 11-13-15 years (n = 1,066, n = 1185 and n = 1,160 in 2004 and n = 1,189, n = 1,211 and n = 1,178 in 2006, respectively). Weights and heights of primary school children were measured by means of standardized methods, while those of adolescents were self-reported. Decimal age was calculated from the date of birth to the date of measurement. Body Mass Index classes were calculated according to the International Obesity Task Force standards. Instead of the term underweight in children, we used the term thinness, which the World Health Organization uses to mean low Body Mass Index for age in adults and adolescents. According to Cole 's recently published cut-offs for thinness, we divided our Body Mass Index values below 18.5 into three grades. Results. This study presents data on the prevalence of different grades of nutritional status (thinness, normal weight, overweight and obesity) among Tuscan school-aged children from primary to high school (9-11-13-15-y-old), assessed by means of Body Mass Index, according to international definitions. From 2002 to 2006 the prevalence of thinness among children aged 9 years decreased from 4.6% to 4.2%, and the prevalence of normal weight from 63.7% to 62.4%; the prevalence of overweight (including obesity) rose from 31.7% to 33.4%. From 2004 to 2006, among pre-adolescents aged 11 years, the prevalence of thinness declined from 11.0% to 10.1%; the prevalence of normal weight rose from 68.4% to 70.2%, and the prevalence of overweight declined from 20.7% to 19.6%. Among adolescents aged 13 years, the prevalence of thinness declined from 9.8% to 8.0%; the prevalence of normal weight rose from 73.5% to 74.0%, and the prevalence of overweight from 16.8% to 17.9%. Among adolescents aged 15 years, the prevalence of thinness declined from 9.8% to 8.7%, and the prevalence of normal weight from 77.0% to 71.6%, while the prevalence of overweight rose from 13.3% to 19.7%. The 2006 data showed that the trend in the prevalence of overweight (including obesity) tended to decrease with age for both sexes, though more markedly in girls (from 34.0% at 9-y of age to 12.2% at 15-y of age) than in boys (from 32.8% at 9-y of age to 22.8% at 13-y of age to 27.5% at 15-y of age). By contrast, the prevalence of thinness increased with age in girls (from 4.9% at 9-y of age to 14,1% at 15-y of age), while boys presented a similar low prevalence at 9 and 15-y of age (3.3% and 3.1%), doubling the values at 11 and 13-y of age (7.5% and 6.5%). The trend in the prevalence of normal weight increased with age from 62.4% at 9-y of age to 74.0% at 13-y of age and to 71.6% at 15-y of age. Boys displayed a higher prevalence than girls only at 9-y of age (63.9% vs. 61.0%). Discussion. The results of this study allow us to analyze data from the nutritional surveillance system in Tuscany using recent definitions of Body Mass Index cut-off points among children, pre-adolescents and adolescents. As a rule, the trend in the prevalence of overweight (including obesity) among girls from 9-y to 15-y-old strongly decreased, while the prevalence of thinness increased. In boys, this decrease was less marked and the prevalence of thinness displayed an irregular trend, with an increment from 9-y to 11-y-old and a decrease from 13-y to 15-y old. The trend in the prevalence of normal weight increased with age, with a higher prevalence among boys than girls.