Dynamics of the components of energy intake between Spanish and Mexican preschool children: energy density and food volume in two contexts.

OBJECTIVE: To determine the differences in the dynamics of dietary energy density (ED), food volume (FV) and energy intake (EI) between two groups of healthy children, in normal conditions, from Spain and Mexico. METHODS: Crossectional study which analyses the habitual diet of two healthy children groups, 1-4 years old, from Reus (Spain, n = 203) and Guadalajara (Mexico, n = 147). Dietary intake was assessed using the 24-hour recall. Anthropometric data were also obtained. We estimated Z-score of weight, height and BMI, and EI (kcal/day), ED (kcal/g), FV (g/day), El/kg body weight (kcal/kg/day) and FV/kg body weight (g/kg/day). RESULTS: The Spanish children consumed significantly more cereals (p < 0.05), vegetables, meat, fish and eggs than the Mexican children (p < 0.001), while the latter consumed significantly more sweets (p < 0.001). The mean El/kg body weight was 107.7 ± 36.2 kcal/kg/day in the children from Reus, and 102.4 ± 38.8 kcal/kg/day in the children from Guadalajara, without significant differences. While the ED was significantly higher (p < 0.001) in the Spanish sample (1.41 ± 0.35 kcal/g) that in the Mexican one (1.19 ± 0.37 kcal/g), we observed the contrary on FV per kilogram of weight: it was significantly (p < 0.001) greater in Mexicans (91.0 ± 36.1 g/kg/day) than in Spanish (79.5 ± 27.5 g/kg/day). CONCLUSION: In two populations with different contexts, the balance between energy intake and energy requirements is achieved in different ways, allowing energy intake per unit of weight and growth to be adequate. Future studies are needed to clarify the factors of a possible alteration of this equilibrium through time, in such a way, that it would probably contribute to the development of overweight and obesity in several environments.

Dynamics of the components of energy intake between Spanish and Mexican preschool children: energy density and food volume in two contexts / Dinámica de los componentes de la ingesta energética entre niños preescolares de España y México: densidad energética y volumen alimentario en dos contextos

Objective: To determine the differences in the dynamics of dietary energy density (ED), food volume (FV) and energy intake (EI) between two groups of healthy children, in normal conditions, from Spain and Mexico. Methods: Crossectional study which analyses the habitual diet of two healthy children groups, 1-4 years old, from Reus (Spain, n = 203) and Guadalajara (Mexico, n = 147).Dietary intake was assessed using the 24-hour recall. Anthropometric data were also obtained. We estimated Z-score of weight, height and BMI, and EI (kcal/day), ED(kcal/g), FV (g/day), EI/kg body weight (kcal/kg/day) and FV/kg body weight (g/kg/day). Results: The Spanish children consumed significantly more cereals (p < 0.05), vegetables, meat, fish and eggs than the Mexican children (p < 0.001), while the latter consumed significantly more sweets (p < 0.001). The mean EI/kg bodyweight was 107.7 ± 36.2 kcal/kg/day in the children from Reus, and 102.4 ± 38.8 kcal/kg/day in the children from Guadalajara, without significant differences. While the ED was significantly higher (p < 0.001) in the Spanish sample(1.41 ± 0.35 kcal/g) that in the Mexican one (1.19 ± 0.37kcal/g), we observed the contrary on FV per kilogram of weight: it was significantly (p < 0.001) greater in Mexicans(91.0 ± 36.1 g/kg/day) than in Spanish (79.5 ± 27.5 g/kg/day).Conclusion: In two populations with different contexts, the balance between energy intake and energy requirements is achieved in different ways, allowing energy in take per unit of weight and growth to be adequate. Future studies are needed to clarify the factors of a possible alteration of this equilibrium through time, in such away, that it would probably contribute to the development of overweight and obesity in several environments (AU)

Objetivo: Determinar las diferencias en la dinámica de la densidad energética (DE), volumen de alimentos (FV) e ingesta energética (IE), entre dos grupos de niños sanos, en condiciones de vida habitual, de España y México. Metodología: Estudio transversal que analiza la dieta habitual de niños sanos, entre 1-4 años, originarios de Reus (España, n = 203) y Guadalajara (México, n =147). La ingesta dietética fue evaluada con el recordatorio de 24 horas. Se valoraron algunos parámetros antropométricos. Se calculó puntuación-Z para el peso, talla e IMC, y la IE (kcal/día), DE (kcal/g), FV (g/día),IE/kg de peso corporal (kcal/kg/día) y FV/kg de peso corporal (g/kg/día).Resultados: Los niños españoles presentaron una mayor ingesta de cereales (p < 0,05), verduras, carne, pescado y huevo, que los mexicanos (p < 0,001), mientras que estos últimos tuvieron una mayor ingesta de azúcares (p <0,001). La media de IE/kg de peso fue de 107,7 ± 36,2kcal/kg/día en niños de Reus, y 102,4 ± 38,8 kcal/kg/día en niños de Guadalajara, sin diferencias significativas. Mientras la DE fue significativamente mayor (p < 0,001)en los españoles (1,41 ± 0,35 kcal/g) que en los mexicanos(1,19 ± 0,37 kcal/g), observamos lo contrario en FV/kg de peso: este fue significativamente mayor (p < 0,001) en los niños mexicanos (91,0 ± 36,1 g/kg/día) que en los españoles(79,5 ± 27,5 g/kg/día).Conclusión: En dos poblaciones con contextos diferentes, el equilibrio de la IE se logra por diferentes vías, permitiendo un aporte energético por unidad de peso y crecimiento adecuados. Se precisan futuros estudios que aclaren los factores mediante los cuales este equilibrio se altera a través del tiempo, y que quizá, contribuye al desarrollo de sobrepeso u obesidad, en diversos entornos (AU)

The prevalence of metabolic syndrome in Latin America: a systematic review.

OBJECTIVE: To assess the available data on the prevalence of metabolic syndrome (MS) in Latin-American countries. DESIGN: Systematic review. Searches were carried out in PubMed, ISIWeb, SCielo and Redalyc, using 'metabolic syndrome x' and 'prevalence' as keywords for titles and/or abstracts. Articles selected were cross-sectional studies in Latin-American countries, whose main objective was to study MS and whose study population is described below. MS must be determined using Adult Treatment Panel III criteria. Twelve studies with these criteria were selected, one of which was multi-centric. SETTING: Latin America. SUBJECTS: Apparently healthy subjects aged 18-65 years (including young adult, mature adult and elderly populations) of both genders. RESULTS: The general prevalence (weighted mean) of MS in Latin-American countries was 24·9 (range: 18·8-43·3) %. MS was slightly more frequent in women (25·3 %) than in men (23·2 %), and the age group with the highest prevalence of MS consisted of those over 50 years of age. The most frequent components of MS were low HDL cholesterol levels (62·9 %) and abdominal obesity (45·8 %). Similar outcomes were obtained from the multi-centre study on Latin-American populations analysed. CONCLUSIONS: The present review brings us closer to an understanding of the prevalence of MS in Latin-American countries. However, it is not possible to know the full scope of the problem, partly because data from some countries are not available, and because the methodological differences among the studies published up to the present limit a joint analysis of their results.

Equation to estimate body weight in elderly Mexican women using anthropometric measurements.

INTRODUCTION: Body weight is useful for many medical and nutritional procedures. When it is difficult or impossible to measure body weight in hospitalized/institutionalized elderly, it can be estimated through equations based on anthropometry generated in other countries, although their validity in other contexts has been poorly studied. OBJECTIVES: To create and validate an equation for estimating body weight for both, hospitalized and nursing home residents Mexican elderly women (institutionalized) using anthropometric measurements. METHODS: A validation study was carried out in elderly women (> or = 60 years old), admitted to the Geriatrics Service of the Hospital Civil de Guadalajara "Fray Antonio Alcalde" during February-April 19th (n = 43) and April 20th-June 2005 (n = 29), and elderly women residing in three nursing homes in the Metropolitan Area of Guadalajara evaluated during June 2003-June 2004 (n = 23). Subjects were weighed using a scale which was adapted to their clinical situation and were anthropometrically assessed. In the first sample, we generated a new equation using multiple regression analyses. Then, the equation was validated in the other two samples. We also estimated weight using Chumlea's equations: in all samples, estimated and actual weights were compared between each other through a paired t-test. A p < 0.05 was considered as significant. RESULTS: Mean ages in each sample were: 84.3 +/- 7.3, 84.4 +/- 9.1, and 84.2 +/- 8.5 years, respectively. Mean actual weights were: 48.2 +/- 13.5, 48.1 +/- 10.1, and 55.0 +/- 12.3 kg, respectively. The resulting equation was: estimated weight = (1.599* knee height) +(1.135* mid arm circumference) + (0.735*calf circumference) + (0.621* tricipital skinfold thickness)-83.123 (R2 = 0.896, p < 0.001). In hospitalized women, there were no significant differences between estimated and actual weight (sample 1:D-0.02 +/- 4.3 kg, p = 0.976; sample 2: D-0.7 +/- 4.2 kg, p = 0.352). In female nursing homes residents (institutionalized women) weight was significantly overestimated (1.9 +/- 3.2 kg p < 0.01), but the mean difference was smaller than the ones found using Chumlea's equations. CONCLUSIONS: The developed equation predicted accurately hospitalized elderly women's body weight in our context. In institutionalized elderly women, weight was significantly overestimated. It would be useful to derive equations for different settings.uals who present normal body weight.

Equation to estimate body weight in elderly Mexican women using anthropometric measurements / Ecuación para estimar peso corporal en ancianas mexicanas a partir de medidas antropométricas

Introduction: Body weight is useful for many medical and nutritional procedures. When it is difficult or impossible to measure body weight in hospitalized/institutionalized elderly, it can be estimated through equations based on anthropometry generated in other countries, although their validity in other contexts has been poorly studied. Objectives: To create and validate an equation for estimating body weight for both, hospitalized and nursing home residents Mexican elderly women (institutionalized) using anthropometric measurements. Methods: A validation study was carried out in elderly women (≥ 60 years old), admitted to the Geriatrics Service of the Hospital Civil de Guadalajara "Fray Antonio Alcalde" during February-April 19th (n = 43) and April 20th-June 2005 (n = 29), and elderly women residing in three nursing homes in the Metropolitan Area of Guadalajara evaluated during June 2003-June 2004 (n = 23). Subjects were weighed using a scale which was adapted to their clinical situation and were anthropometrically assessed. In the first sample, we generated a new equation using multiple regression analyses. Then, the equation was validated in the other two samples. We also estimated weight using Chumlea's equations: in all samples, estimated and actual weights were compared between each other through a paired t-test. A p < 0.05 was considered as significant. Results: Mean ages in each sample were: 84.3 ± 7.3, 84.4 ± 9.1, and 84.2 ± 8.5 years, respectively. Mean actual weights were: 48.2 ± 13.5, 48.1 ± 10.1, and 55.0 ± 12.3 kg, respectively. The resulting equation was: estimated weight = (1.599* knee height) +(1.135* mid arm circumference) + (0.735*calf circumference) + (0.621* tricipital skinfold thickness)-83.123 (R2 = 0.896, p < 0.001). In hospitalized women, there were no significant differences between estimated and actual weight (sample 1:D-0.02 ± 4.3kg, p = 0.976; sample 2: D-0.7 ± 4.2 kg, p = 0.352). In female nursing homes residents (institutionalized women) weight was significantly overestimated (1.9 ± 3.2 kg p < 0.01), but the mean difference was smaller than the ones found using Chumlea's equations. Conclusions: The developed equation predicted accurately hospitalized elderly women's body weight in our context. In institutionalized elderly women, weight was significantly overestimated. It would be useful to derive equations for different settings.uals who present normal body weight (AU)

Introducción: El peso corporal es útil para llevar a cabo diversos procedimientos médicos y nutrimentales. Cuando se dificulta o es imposible medir el peso corporal en ancianos hospitalizados/institucionalizados, se puede estimar a partir de ecuaciones basadas en antropometría, generadas en otros países, aunque su validez en otros contextos ha sido poco estudiada. Objetivos: Crear y validar una ecuación para estimar peso corporal, tanto en ancianas hospitalizadas, como institucionalizadas en asilos, usando medidas antropométricas. Métodos: Se llevó a cabo un estudio de validación en ancianas (≥ 60 años), admitidas al Servicio de Geriatría del Hospital Civil de Guadalajara "Fray Antonio Alcalde" en el periodo Febrero-Abril 19 (n = 43) y Abril 20-Junio 2005 (n = 29), y ancianas residentes de tres asilos en la Zona Metropolitana de Guadalajara evaluadas en el periodo Junio 2003-Junio 2004 (n = 23). Los sujetos fueron pesados utilizando una báscula adaptada a su situación clínica y se les realizó una evaluación antropométrica. Con la primera muestra, generamos una nueva ecuación mediante análisis de regresión múltiple. Después, la ecuación se validó en las otras dos muestras. Asimismo, se estimó el peso mediante las ecuaciones de Chumlea: en todas las muestras, se compararon los pesos estimados con el real mediante un t-test pareado. Se consideró una p < 0.05 como significativa. Resultados: El promedio de edad para cada muestra fue: 84.3 ± 7.3, 84.4 ± 9.1, y 84.2 ± 8.5 años, respectivamente. El promedio de peso fue: 48.2 ± 13.5, 48.1 ± 10.1, y 55.0±12.3 kg, respectivamente. La ecuación resultante fue: peso estimado = (1.599* altura talón-rodilla) + (1.135* circunferencia media de brazo) + (0.735* circunferencia de pantorrilla) + (0.621* pliegue cutáneo tricipital)- 83.123 (R2 = 0.896, p < 0.001). En las mujeres hospitalizadas no se encontraron diferencias estadísticamente significativas entre los pesos estimados y el real (muestra 1: D-0.02 ± 4.3 kg, p = 0.976; muestra 2: D-0.7 ± 4.2 kg, p = 0.352). En las ancianas residentes de asilos (mujeres institucionalizadas) el peso se sobreestimó de manera significativa (1.9 ± 3.2 kg p < 0.01), aunque el promedio de las diferencias fue menor que el encontrado con las ecuaciones de Chumlea. Conclusiones: La ecuación desarrollada estimó de manera precisa el peso corporal de las ancianas hospitalizadas en nuestro contexto. En mujeres institucionalizas, el peso fue sobreestimado de manera significativa. Sería útil derivar ecuaciones para diferentes contextos (AU)

Body fat at pubertal genital stage 2: a comparison between Spanish and Mexican boys.

BACKGROUND/OBJECTIVES: To compare body fat mass at the same stage of pubertal maturation, genital stage 2 (G2), in a Spanish and in a Mexican sample of boys. SUBJECTS/METHODS: Data from Spain (n=177) were from a previous longitudinal clinical follow-up and data from Mexico (n=91) from a cross-sectional study. Subjects were grouped according to the presence of G2 at similar ages. Spanish sample was divided into boys with G2 at age 12 (n=60), 13 (n=74) and 14 (n=43). In Mexican sample, 23 boys were at G2 at 12 years, 38 at age 13 and 30 at 14 years. Height, weight, upper arm circumference and four skinfold thicknesses were recorded. Genital development was assessed (Tanner scale). Sum of four skinfolds (SUM), body mass index (BMI), percentage of body fat (%BF) and extremity/trunk skinfold ratio (ETR=(triceps+biceps)/(subscapular+suprailiac)) was calculated. RESULTS: When comparing subjects with different ages at G2 from the same country, or with the same age at G2 from different countries, no significant differences were found in adiposity variables (%BF, SUM), nor in BMI. Nevertheless, there were differences in body fat distribution: ETR was higher in Spanish boys (P<0.001), because of their greater triceps skinfold thickness (P=0.013), and due to the greater trunk fat stores in Mexican boys (P<0.01, subscapular and suprailiac skinfolds). CONCLUSIONS: There is a subcutaneous fat mass store characteristic of G2 in boys, which is not only independent of age, but is also observable in two different populations.

Onset of puberty at eight years of age in girls determines a specific tempo of puberty but does not affect adult height.

AIMS: To analyse the effect of early puberty (onset between 7.5 and 8.5 y) on pubertal growth and adult height in girls, and the implications of this effect for the age limit for normal onset of puberty. METHODS: Longitudinal study in Reus (Spain) of 32 girls with early puberty until they reached adult height. Data from these girls were compared with longitudinal data from girls (116) from the same population with normal onset at 10 (n = 37), 11 (n = 47), 12 (n = 19) and 13 (n = 13)y. We analysed height, target height, adult height, pubertal height increase, duration of pubertal growth, age at menarche and time to menarche. RESULTS: The adult height of girls with early puberty (160.9 +/- 5.4cm) was similar to that of girls with onset at later ages (p = not significant). In these girls, puberty lasted 5.4 +/- 0.7 y and the mean growth during puberty was 31.1 +/- 3.5 cm. As the age of onset of puberty increases, the duration of puberty and mean growth during puberty progressively decreased (p < 0.001). Girls with early puberty reached menarche at a mean age of 10.9 +/- 1.0 y, 3.2 +/- 0.9 y after onset of puberty, and this time span was greater than in the other groups. CONCLUSION: Girls with onset of puberty at 8 y show all the compensatory phenomena related to height at onset, pubertal duration and height increase during puberty. These phenomena cause their adult height to be similar to that of girls who begin puberty at the age of 10 to 13 y.

Age of pubertal onset affects the intensity and duration of pubertal growth peak but not final height.

This paper analyzed the intensity and duration of height growth during puberty in boys and girls in relation to rhythm of maturation. A longitudinal clinical follow-up between ages of 10 and 20 years, was carried out in a sample of 251 children grouped according to age at pubertal onset: boys (genital stage 2) at the ages of 11 (n = 28), 12 (n = 38), 13 (n = 42), and 14 (n = 27); and girls (breast stage 2) at the ages of 10 (n = 37), 11 (n = 47), 12 (n = 19), and 13 (n = 13). Height was measured annually. Testicular volume and genital development were assessed in boys, and breast development was assessed in girls. There were significant differences (P < 0.001) in height at the age of pubertal onset among maturity groups. Late maturers were taller than early maturers (r = 0.49, P < 0.001 for girls; r = 0.38, P < 0.001 for boys). However, final heights did not differ according to age of onset in either sex. In boys, later onset of puberty was associated with a smaller pubertal height gain (r = -0.60, P < 0.001) and a shorter period of pubertal growth (r = -0.61, P < 0.001). Equally in girls, earlier onset of puberty was associated with a greater pubertal height gain (r = -0.68, P < 0.001) and a longer period of pubertal growth (r = -0.59, P < 0.001). In conclusion, age of pubertal onset does not affect final height attained in both sexes, since there is an inverse compensatory phenomenon in both sexes between height at pubertal onset and the intensity and duration of pubertal growth.

Puberty begins with a characteristic subcutaneous body fat mass in each sex.

OBJECTIVE: To observe whether there exists a characteristic body fat mass at pubertal onset. DESIGN: Longitudinal clinical follow-up (between ages of 10 and 15 y) with an annual visit in a sample of 469 children. They were grouped according to age of purbertal onset: boys with pubertal onset at the ages of 11 (n=59), 12 (n=88), 13 n=89) and 14 y (n=46), and girls with pubertal onset at the age of 10 (n=68), 11 (n=66), 12 (n=37) and 13 (n=16). METHODS: Height, weight, upper arm circumference and four skinfold thicknesses were recorded annually. In boys testicular volume index was measured, and genital development was assessed on the Tanner scale; in girls mammary development was measured also using the Tanner scale. The sum of four skinfolds, body mass index, upper arm fat estimate and percentage body fat were calculated. RESULTS: Boys presented a positive relation between the age of pubertal onset and body mass index (P<0.001), which was not observed in girls. Body mass index thus varied according to the onset of puberty in boys (P<0.001), but not in girls. The sum of four skinfolds, the upper arm fat estimate index and the percentage of body fat mass did not differ according to age of pubertal onset either in girls (P=NS) or in boys (P=NS). The characteristic adiposity of the puberty onset is progressively acquired during the previous years in all the groups. CONCLUSIONS: Puberty seems to begin with a characteristic subcutaneous body fat mass that is independent of the age of onset. This study supports the hypothesis of a close link between maturation and the development of an energy store in the form of adipose tissue in both sexes.

Energy density of the diet, food volume and energy intake by age and sex in a healthy population.

OBJECTIVE: To assess the changes in energy intake (EI), food intake volume (FV) and energy density (ED) related to age and gender in a population in the Mediterranean area of Spain, and to determine the different role of FV and ED on the consecution of the adequate EI throughout lifespan. SUBJECTS: One thousand and eighty-eight individuals (1-65 y) randomly selected from the population census. DESIGN: Cross-sectional study in which food intake was quantified by 24 h dietary recall, three non-consecutive days. Height and weight measurements were taken in 885 individuals. RESULTS: EI, FV and ED increased progressively (P < 0.001) between 1-2 y and 10-12 y of age in both sexes. At 1-2 y the EI is 5.8+/-1.5 MJ/d, FV 1195+/-275 g/d and ED 4.8+/-0.9 kJ/g. Between 1-2 and 3-4 y, coinciding with an EI that increased up to 7.2+/-1.5 MJ/d, there was an increase in ED up to 6.1+/-0.8 kJ/g (P < 0.001), while the FV did not vary significantly. At the start of puberty, between 7-9 and 10-12 y, when the EI increased to 9.7+/-0.9 MJ/d (P < 0.001) in males, the ED rose to 7.1+/-0.9 kJ/g (P < 0.001) while the FV did not vary significantly. At this age, a significant difference between the genders was observed in the EI (P = 0.04), and in the ED (P = 0.02) but not, as yet, in the FV. During adulthood, a significant trend towards decrease (P < 0.001 in both sexes) was observed in EI and ED. However, FV decreased significantly only in females. CONCLUSIONS: The changes in energy intake that were observed with respect to age and gender were accommodated-for by changes in the ED of the diet rather than by variations in food volume intake. Autoregulation of the ED of the diet, sufficient for energy intake requirement changes, appears to be an essential human capacity for efficient nutrition.

Implications of the weaning pattern on macronutrient intake, food volume and energy density in non-breastfed infants during the first year of life.

OBJECTIVES: To evaluate the implications of the patterns of weaning on the intake of macronutrients, energy intake, food volume and the energy density in healthy infants in the Mediterranean area of Spain. SUBJECTS AND STUDY DESIGN: Cross-sectional study of 120 clinically-healthy, non-breastfed infants at the ages of 4, 6, 9 and 12 months randomly recruited from three pediatric out-patient clinics. Nutrition data were obtained from the infant's food preparer using the 24-hour dietary recall method. RESULTS: Energy intake/kg body weight was within the recommended daily allowance and did not vary significantly with age (423 kJ/kg body weight at 4 months and 443.7 kJ/kg at 12 months). There was a progressive decrease in the intake volume (p < 0.001) in which carbohydrate-rich foodstuffs were the major factors, and an increase in the energy density (p < 0.001) in which the protein-rich items were the principal contributors. Lipid intake diminished progressively (p < 0.01) to a nadir of 26.4% of energy intake at 9 months of age. In each of the meals there was a tendency towards a progressive increase in energy intake with age. This increase was achieved by a significant increase in energy density (p < 0.001 in all meals, except dinner p < 0.05). Conversely, the intake volume of breakfast, lunch and dinner remained essentially unchanged between 6 and 12 months while that of the mid-evening meal decreased markedly. CONCLUSION: Increased energy requirements for growth is achieved, mainly, by an increase in the energy density rather than the intake volume during food-item diversification in the non-breastfed infant. Cereals were the central food item in the weaning diet in our study sample and which adequately compensates, in terms of energy requirement, for the early reliance on the lipids contained in milk.

The duration of puberty in girls is related to the timing of its onset.

OBJECTIVE: To observe the time lapse between the start of puberty and the advent of menarche in groups of girls maturing at different ages. SUBJECTS: A sample of 163 girls subgrouped by pubertal onset at 9 (n = 22), 10 (n = 53), 11 (n = 54), 12 (n = 27), and 13 (n = 7) years of age. DESIGN: Clinical follow-up from 10 to 17 years of age. METHODS: Onset of puberty was defined by the combined observation of mammary development on the Tanner scale and the height curve. The date of menarche was recorded (month and year), and the time lapse was expressed as a function of the date of birth. RESULTS: In the overall study sample, the duration of puberty was 1.96 +/- 0.06 years. For the subgroups of girls starting puberty at 9, 10, 11, 12, and 13 years of age, the time lapse to menarche was 2.77 +/- 0.16, 2.27 +/- 0.16, 1.78 +/- 0.08, 1.44 +/- 0.10, and 0.65 +/- 0.09 years, respectively (p < 0.001). The correlation coefficient (r) between the onset of puberty and its duration was r = -0.62 (p < 0.001), and that of age of pubertal onset versus age of menarche was r = 0.66 (p < 0.001). CONCLUSION: The duration of puberty in girls depends on the timing of its onset; the earlier the onset of puberty the longer its duration.