Body mass index in children and adolescents according to age and pubertal stage

Abstract

Objective: To evaluate the dependence of body mass index (BMI) values on pubertal stage in subjects similar in age. Design, subjects and measurements: Height and weight were recorded cross-sectionally in school subjects from three provinces in central Italy. The subjects were subdivided into three groups: (1) 4271 school subjects (2125 males and 2146 females; 8.5 ± 15.5 y old), in whom the pubertal development was also recorded, were selected to subdivide BMI values according to pubertal stage and age; (2) 6345 females (10.5 ± 14.5 y old), who were asked whether or not they had had their ®rst menstrual period, were selected to subdivide BMI values according to age in pre-menarche and post-menarche girls, separately; and (3) 1919 females (10.5 ± 14.5 y old), who had presented their menarche within the previous 6 months, were selected to subdivide short-term postmenarche BMI values according to age. Results: The medians and interquartile ranges of BMI varied according to age and pubertal stage. Kruskall ± Wallis test performed in subjects similar in age demonstrated that signi®cant differences existed among the medians of BMI values of subjects at different pubertal stages in 12 ± 14-y-old males (P`0.05), and in 11 ± 14-yold females (P`0.001). The difference also proved to be signi®cant between stage I and stage II (P`0.05) in 10-y-old females, but not in 10 ± 11-y-old males. The Kruskal ± Wallis test performed in subjects similar in pubertal stage demonstrated that signi®cant differences among the medians of BMI at different ages existed only in females at stages II and III. A signi®cant positive trend was observed in both genders according to pubertal stage for BMI values of subjects similar in age (z-test for trend, P`0.01). On the contrary, a negative age trend proved to be signi®cant in females at stages I (P`0.01), II (P`0.01) and III (P`0.001), but not in males when the subdivision of BMI was made according to age in subjects similar in pubertal stage. BMI values were signi®cantly higher in post-menarche girls as compared to pre-menarche girls similar in age (P`0.001). However, at partial regression analysis BMI values were in¯uenced by pubertal stage and, to a lesser extent, by age, but not by menarcheal status. An inverse association between short-term post-menarche BMI and age was observed, with the highest values in girls presenting menarche at 11 y of age (P`0.05). The negative trend was demonstrated at the z-test for trend (P`0.001). Conclusions: BMI values depend on pubertal degree of maturation, especially in girls. This in¯uence should be taken into account when BMI is evaluated in adolescents.

Prevalence of overweight and obesity among Bahraini adolescents: a comparison between three different sets of criteria

“…90th percentile of subscapular skinfold). As a result, when these cut-offs were applied to the data set, participants with BMI values at or above the 85th percentile and with high subcutaneous fat were shifted from the overweight category to the obese category, resulting in lower estimates of overweight and higher estimates of obesity than those determined by other standards such as those of Must et al (1991) and Cole et al (Daniels et al, 1997;Bini et al, 2000). In the present study however, pubertal staging was not performed due to some cultural constraints.…”

Identifying adolescents with high percentage body fat: a comparison of BMI cutoffs using age and stage of pubertal development compared with BMI cutoffs using age alone

“…Falorni et al (1998) and Bini et al (2000) both used the LMS method of Cole (1990) to create Z-score distributions for BMI in Italian children. The data set of Falorni et al (1998) was created from measurements collected in the period 1993-97 in more than 30 000 children and adolescents aged 3-18 y from whom Z-scores for age were derived.…”

“…As more mature boys and girls have higher BMI values than their less-developed counterparts of similar age (O'Dea & Abraham, 1995;Bini et al, 2000), the use of agespecific cutoffs for BMI in adolescents ignores the potentially important contribution of puberty (Bini et al, 2000). In turn, it seems possible that these more mature children may have an increased chance of being erroneously classified as overweight.…”

“…These studies have generally reported that while BMI has reasonable efficacy for identifying children who are truly lean, it appears to be relatively insensitive at identifying children who are truly fat. However, because BMI values vary according to degree of sexual maturity in adolescents of the same chronological age (Bini et al, 2000), it is possible that a knowledge of both chronological age and pubertal status is required for the appropriate identification of obesity. To our knowledge, no studies appear to have established whether or not this is true.…”

“…Thus, the aim of this study was to ascertain whether BMI cutoffs developed according to both age and pubertal stage of development (Bini et al, 2000) were superior at classifying children as obese according to their percentage body fat compared with BMI cutoffs calculated on the basis of chronological age alone (Falorni et al, 1998).…”