Four hundred one (401) boys, from ten different U.S. locations, participated in this study, one of the few studies to have analyzed weight differences in boys and puberty.
The researchers examined the boys' body mass index (BMI) and the onset of puberty within the boys.
Each boy was participating in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development.
BMI measurements were taken at the ages of two, three, 4.5, seven, nine, 9.5, 10.5 and 11.5 years. Puberty was measured based on Tanner genitalia staging.
The researchers found that the boys that were obese (excessively overweight) are twice as likely, when compared to boys with normal weights, to not have started puberty by the age of 11.5 years.
Specifically, the study found that 14% of obese boys had not started puberty when the study ended, while only 7% of normal-weight boys had not started puberty at that same time.
Page two continues with quotes from the lead author of the recently-conducted study, Dr. Joyce Lee.
According to the abstract to their paper: 'Boys in the highest BMI trajectory (mean BMI z score at age 11.5 years, 1.84) had a greater relative risk of being prepubertal compared with boys in the lowest BMI trajectory (mean BMI z score at age 11.5 years, -0.76) ....'
The researchers of this study concluded, 'The relationship between body fat and timing of pubertal onset is not the same in boys as it is in girls. Further studies are needed to better understand the physiological link between body fat and timing of pubertal onset in both sexes.' [Abstract]
U.S. pediatric endocrinologist Joyce M. Lee (from the University of Michigan, Ann Arbor), the lead author of the study, stated, "With the epidemic of childhood obesity, there's concern this is going to have a negative effect on growth and development.' [ABC News]
The results of the study are published in the February 2010 issue of the journal Archives of Pediatric and Adolescent Medicine under the title 'Body Mass Index and Timing of Pubertal Initiation in Boys' (Arch Pediatr Adolesc Med, Feb 2010; 164: 139-144).
Along with Dr. Joyce Lee (who is also associated with the Division of Pediatric Endocrinology, Child Health Evaluation and Research Unit at the University of Michigan), its other authors are Niko Kaciroti (University of Michigan), Danielle Appugliese (Boston University), Robert F. Corwyn (University of Arkansas), Robert H. Bradley (Arizona State University), and Julie C. Lumeng (University of Michigan).
Page three discusses why Dr. Lee and her associates are uncertain about the specific cause of obese boys having a delayed onset of puberty.
Because so few studies have been made on obese boys and puberty, it remains unclear why this association exists in boys (obese boys have an 'delayed' onset of puberty over normal weight boys) but not in girls (obese girls have an 'earlier' onset of puberty over normal weight girls).
Further studies on boys and puberty will need to be undertaken to find the cause of this delayed puberty in obese boys.
Lee concludes, "I think the fact that obesity could affect how they currently grow and develop could be of greater concern to parents because that affects them in the short term.' [ABC News]
Plot the height and weight of your children at: Growth Charts for Boys and Girls.
Check out information for body mass index (BMI) at the U.S. Centers for Disease Control and Prevention (CDC) website About BMI for Children and Teens.