Is Obesity Associated With Early Sexual Maturation?
Zvi Laron, MDEndocrinology and Diabetes Research Unit Schneider Children’s Medical Center Tel Aviv University Petah Tikva 49202, Israel
To the Editor.—
I read with interest the article by Dr Wang1 and would like to share with you our experience in a different population, performing a close follow-up study.2 We analyzed in detail the auxology and the appearance and size of pubertal signs compared to weight and skinfolds in boys and girls with simple obesity between the 10 and 16 years old.
All were Israeli-born Jews referred and followed because of simple obesity. The group consisted of 136 boys, 41 girls, and 48 age-matched, randomly selected, healthy boys and 48 healthy girls. Our main statistically significant findings were as follows: At all ages, the obese boys were taller and their bone age more advanced than the controls up to age 14 (P < .01 and .001). There was no difference between the two male groups in the time of appearance and development of axillary or pubic hair, moustache, beard, acne or breaking of the voice, testicular volume, and penile size. The mean overall pubertal score and age of first ejaculation3 were also similar.
The obese girls were taller than the controls up to age 14, with a statistically significant difference between 11 and 13 (P < .001). The bone age was significantly advanced between 9 and 11 years (P < .01), but there was no significant difference in the age of appearance and development of the breasts, pubic hair, genitalia, or age at menarche. There were two additional small groups of obese girls: 8 with obesity and tall stature but without sexual precocity and 12 obese girls with precocious puberty. The degree of obesity in these girls was not different from those with so-called simple obesity, and therefore we concluded that these developmental characteristics were hereditary.
An additional finding was that parents of the obese children were significantly overweight (P < .01) compared with the parents of the controls, supporting the opinion of Schwarz4 that obesity is a hereditary disorder with familial faulty dietary habits. We concluded that our data do not support the hypotheses of a "critical weight factor" determining sexual maturation.
REFERENCES
- Wang Y. Is obesity associated with early sexual maturation? A comparison of the association in American boys versus girls. Pediatrics.2002; 110
:903
–910
[Abstract/Free Full Text] - Laron Z, Ben-Dan I, Shrem M, et al. Puberty in simple obese boys and girls. In: Cacciari E, Laron Z, Raiti S, eds. Obesity in Childhood. London, United Kingdom: Academic Press;1978 :29 –40
- Laron Z, Arad J, Gurewitz R, et al. Age at first conscious ejaculation: A milestone in male puberty. Helv Paediatr Acta.1980; 35 :13 –20[Web of Science][Medline]
- Schwarz F. Growth and development of obese children. In: van der Werff Ten Bosch JJ, Hjaak A, eds. Somatic Growth of the Child. Leiden, The Netherlands: H. E. Stenfert Kroese N.V.;1966 :174 –180
Youfa Wang, MD, PhD
Department of Human Nutrition Division of Epidemiology and Biostatistics University of Illinois Chicago, IL 60612, USA
In Reply.—
Dr Laron compared obese adolescents born in Israel (136 boys and 41 girls) with 96 age-matched, randomly selected, healthy boys and girls between 10 and 16 years old.1 They found that, in general, these obese boys and girls were taller than nonobese adolescents, and their bone age was more advanced during early adolescence, but there were no significant differences in the indicators of sexual maturation (SM) status between the obese and nonobese groups for each gender. Their findings, along with other recent studies, highlight the current controversies regarding the relationship between obesity and SM. We suspect that their study may be limited by the study design and its statistical power due to the relatively small number of nonobese subjects.
Overall, the large majority of published studies have shown a close association between obesity and early SM in females, although the results are limited and less consistent for males. The associations have been indicated by both cross-sectional and longitudinal data and by studies conducted since the 1970s. Frisch et al2,3 developed the "critical weight (fat) theory" in the 1970s suggesting that a critical body weight or body fatness is needed for the onset of menarche based on the observation that heavier girls mature earlier. They argued that this theory makes sense from an evolutionary point of view—females need to accumulate adequate body energy reserves for preparing to produce offspring. However, other researchers have questioned this theory and argued that SM influences the accumulation of adipose tissue, or it at least has a greater effect on fatness.4–9
Recently, based on national representative data collected from large samples of American adolescents, both our study and that of Adair and Gordon-Larsen10 show a strong association between SM and obesity. Consistently, we found that earlier maturing girls were much heavier than their counterparts, whereas our study shows that earlier maturing boys were thinner. Studying a large sample of Italian children, Bini et al11 found that children at more advanced SM stages tended to have higher body mass indices (BMIs). They concluded that SM had a greater influence on BMI than age in both genders. However, such cross-sectional studies cannot prove causality, because SM and obesity are measured at the same time point. Longitudinal data are needed to test the causal direction. Increasingly, longitudinal studies confirm the linkage between SM and obesity, but the conclusions regarding the causality are mixed. For example, He and Karlberg13 followed a large cohort of Swedish children and found that higher BMI gain in children (between 2 and 8 years old) was related to an earlier onset of puberty (measured by using age at peak height velocity) in both genders; the impact was 0.13 years for an increase of 1 BMI unit.14 Another study from Spain found that later onset of puberty was associated with higher BMIs in boys but found no association between the two in girls.15 Studies with longer follow-up periods provide evidence showing that girls who had menarche earlier were more likely to become obese adults,7,8 although it is possible that this association may become weaker if the influence of childhood obesity on both SM and adult obesity were controlled for, because overweight adolescents are likely to remain obese as adults.16
A number of hypotheses have been proposed to explain the association between SM and obesity.17 Several hormonal factors may help to explain the linkage. Among them, leptin, a protein made in adiposytes, is of great interest, but emerging evidence suggests that it is a permissive factor, not a trigger, for the onset of puberty.14,17 Further longitudinal research will help advance our understanding of the complex relationships between obesity and SM.
REFERENCES
- Laron Z. Is obesity associated with early sexual maturation [letter]? Pediatrics.2003; 113 :171 –172
- Frisch RE, McArthur JW. Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset. Science.1974; 185
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[Abstract/Free Full Text] - Frisch RE, Revelle R. Height and weight at menarche and a hypothesis of critical body weights and adolescent events. Science.1970; 169
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[Abstract/Free Full Text] - Trusell J. Menarche and fatness: reexamination of the critical body composition hypothesis. Science.1978; 200
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[Free Full Text] - Trusell J. Statistical flaws in evidence for the Frisch hypothesis that fatness triggers menarche. Hum Biol.1980; 52 :711 –720[Web of Science][Medline]
- Scott EC, Johnston FE. Critical fat, menarche, and the maintenance of menstrual cycles: a critical review. J Adolesc Health Care.1982; 2 :249 –226[CrossRef][Medline]
- Bronson FH, Manning JM. The energetic regulation of ovulation: a realistic role for body fat. Biol Reprod.1991; 44 :945 –950[Abstract]
- Garn SM, LaVelle M, Rosenberg KR, Hawthorne VM. Maturational timing as a factor in female fatness and obesity. Am J Clin Nutr.1986; 43
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[Abstract/Free Full Text] - Van Lenthe FJ, Kemper CG, van Mechelen W. Rapid maturation in adolescence results in greater obesity in adulthood: the Amsterdam Growth and Health Study. Am J Clin Nutr.1996; 64
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[Abstract/Free Full Text] - Wang Y. Is obesity associated with early sexual maturation? A comparison of the association in American boys versus girls. Pediatrics.2002; 110 :903 –910
- Adair L, Gordon-Larsen P. Maturational timing and overweight prevalence in US adolescent girls. Am J Public Health.2001; 91 :642 –644[Abstract]
- Bini V, Celi F, Berioli MG, et al. Body mass index in children and adolescents according to age and pubertal stage. Eur J Clin Nutr.2000; 54 :214 –218[CrossRef][Web of Science][Medline]
- Vizmanos B, Marti-Henneberg C. Puberty begins with a characteristic subcutaneous body fat mass in each sex. Eur J Clin Nutr.2000; 54 :203 –208[CrossRef][Web of Science][Medline]
- He Q, Karlberg J. BMI in childhood and its association with height gain, timing of puberty, and final height. Pediatr Res.2001; 49 :244 –251[Web of Science][Medline]
- Karlberg J. Secular trends in pubertal development. Horm Res.2002; 57(suppl 2) :19 –30
- Vizmanos B, Marti-Henneberg C. Puberty begins with a characteristic subcutaneous body fat mass in each sex. Eur J Clin Nutr.2000; 54 :203 –208
- Serdula MK, Ivery D, Coates RJ, Freedman DS, Williamson DF, Byers T. Do obese children become obese adults? Prev Med.1993; 22 :167 –177[CrossRef][Web of Science][Medline]
- Delemarre-van de Waal HA, van Coeverden SC, Engelbregt MT. Factors affecting onset of puberty. Horm Res.2002; 57(suppl 2) :15 –18
PEDIATRICS (ISSN 1098-4275). ©2004 by the American Academy of Pediatrics
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