Fig. 7

Guide for prospective use of the pubertal-age-adjusted reference for total BMI (kg/m² and kg^0.5/m) and total height (cm) for girls (♀) and boys (♂). Individual age adjustment is made using only the height measurement at the chronological age (C-age) at which puberty started (see upper left traditional C-age-reference for girls and boys) [14], by using the height increase from the individual prepubertal growth curve (as drawn in upper left panel) through the individual measuring points. This measurement is usually corresponding to the time when secondary sex characteristics develop; early breast development stage, B2 in girls (red, upper left panel), or testicular volume increase to 4–6 ml in boys (blue, upper left panel). Individual growth curves are shown for a girl aged 8 years and a boy aged 13-years at the start of puberty [14]. Height and BMI according to C-age and P-age, i.e. the age adjusted to reflect the start of puberty, are shown for an 8-year-old girl and a 13-year-old boy [14]. Height (cm) and BMI (in kg/m² or kg^0.5/m) according to C-age at the onset of puberty, and to P-age, after adjustment for age at onset of the pubertal growth spurt, are depicted as red dots (all panels), based only on age in the height references for each sex, respectively. Corresponding heights and BMIs are then moved to puberty-adjusted age = zero, in the P-age-references shown in the lower panels (left panels for height and right for BMI). Thereafter, all measured heights and BMIs are depicted at ages/times recalculated in relation to the specific onset of puberty in that individual, labelled on the x-axis as ‘Time from onset of growth spurt (years)’. Thus, changes in BMI and height in the years preceding the pubertal growth spurt can be evaluated using the novel references. Note, the BMI increase precedes the height increase in relation to puberty. For corresponding values for weight, see Fig. 7 in Albertsson-Wikland et al. [16]