Background: Since populations are becoming increasingly multi-ethnic, the use of local or international charts is a matter of debate. This study aimed to evaluate how the choice of cut-off thresholds affected prevalence of underweight (UW), overweight (OW), obesity (OB) in 1200 11–12-year Italian adolescents, and how their somatic growth depended on parental origin.

Methods: The height, weight and body mass index were expressed as standard deviation score (SDS) using Italian (ISPED-2006) and UK (UK-1990) charts. The classification of UW/OW/OB was computed with the IOTF international cut-offs, and thresholds were identified as centiles corresponding to BMI values of 18.5/25.0/30.0 kg/m² at 18-year in ISPED-2006 or UK-1990 references.

Results: About 30% participants had non-Italian parents, above all from North-Africa and Romania. Referring to the UK-1990 charts, all groups showed negative mean SDS for height, and positive SDS for weight and BMI. Referring to the ISPED-2006 charts, all mean SDS were negative. Percentage of UW individuals was higher in accordance with ISPED-2006 than with UK-1990 charts, whereas percentages of OW/OB were higher with UK-1990 than ISPED-2006 charts. The results obtained using IOFT cut-off s were similar to UK-1990 cut-off s. These results were due to the different shape of age-dependent cutoff centiles. Independently by the parental origin, the percentages of adolescents classified as OW/OB were closer to the expected values using the ISPED-2006 then the UK-1990 cut-off s. The results suggested the use of the Italian references for adolescents with immigrant parents.