International waist circumference percentile cut-offs for central obesity in children and adolescents aged 6-18 years by Xi, B, Zong, X, Kelishadi, R, Litwin, M, Hong, YM, Poh, BK, Steffen, LM, Galcheva, SV, Herter-Aeberli, I, Nawarycz, T, Krzywińska-Wiewiorowska, M, Khadilkar, A, Schmidt, MD, Neuhauser, H, Schienkiewitz, A, Kułaga, Z, Kim, HS, Stawińska-Witoszyńska, B, Motlagh, ME, Ruzita, AT, Iotova, VM, Grajda, A, Ismail, MN, Krzyżaniak, A, Heshmat, R