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Obese boys tended to lag behind boys of normal weight in their pubertal development, according to a large, community-based, racially diverse study.

Based on data gathered from 2005-2010, each boy was measured for height and weight and classified as obese, overweight, or normal weight based on body mass index (BMI). The boys' pubertal development was assessed according to the (1-5), explained , of the University of Michigan in Ann Arbor, and colleagues.

While there wasn't a consistent relationship between weight and onset of puberty, obese boys reached Tanner stage 5 at an average of 15.4 years compared to 14.5 years for overweight boys and 15.2 years for normal weight boys (P=0.001 for both), they wrote in .

However, the authors also reported that overweight, as opposed to obese, boys reached some stages of puberty earlier, suggesting the relationship between body fat and pubertal timing in boys may not be straightforward or linear.

"Our findings represent a unique contribution to our understanding of the complex relationship between boys' puberty, overweight, and obesity," Lee and colleagues wrote. "The relationship between pubertal timing and body fat in boys may be nonlinear, prompting the need for further clinical and mechanistic studies to evaluate pubertal outcomes and hormone levels across a spectrum of weight categories.

"This is important information for pediatricians who are monitoring children for growth and development, because the findings are potentially the opposite of what you see in girls," Lee told 番茄社区app in an email. "In girls, . Pediatricians should consider the possibility that delayed puberty in boys may be due to obesity."

But in an interview with 番茄社区app, , at the Children's National Health System in Washington, commented that the study findings were "puzzling ... the implication that there is a difference between overweight and obesity. It's hard to explain why overweight has one effect and obesity has another."

"It is well known that ," added Kaplowitz who was not involved in the study. "I think the situation in boys is much less clear cut."

Previous studies on weight and puberty in boys have yielded mixed results, noted Kaplowitz, who is the past chair of the American Academy of Pediatrics (AAP) section on endocrinology.

"For the practicing pediatrician, there are not any great implications here except to reinforce that the impact of extra weight on pubertal development is different between girls and boys," Kaplowitz said.

Lee's group analyzed data on more than 3,800 boys, ages 6-16, who were part of the AAP study. Roughly half the boys were white, one-quarter were African American, and one-quarter Hispanic.

They used to classify the participants into three categories:

• Normal weight (BMI 5th to 84th percentile)
• Overweight (BMI ≥85th and <95th percentile)
• Obese (BMI ≥95th percentile)

They found that overweight boys reached Tanner stage 5 at an average of 14.5 years compared to 15.2 years for boys of normal weight (P=0.001). Overweight boys also reached Tanner stage 2 at an average of 9.3 years versus 10 years for normal weight boys (P=0.008).

Obese African-American boys also tended to hit puberty later than their normal weight counterparts, reaching Tanner stage 4 at an average of 13.2 years compared with 12.6 years for normal weight boys (P=0.006).

Lee and colleagues found no significant differences in the timing of puberty according to weight category for Hispanic boys.

"It has been hypothesized that aromatase activity from adipose tissue may lead to excess estrogen production in boys, leading to possible delays in puberty; therefore one might expect a linear association between fat mass and timing of puberty," they stated. "However, given the earlier onset of puberty we found for overweight boys, and the later onset of puberty for obese boys, we speculate that it is possible that greater estrogen production in the obese boys could be suppressing the pubertal process for obese, but not overweight, boys."

Limitations of the study included cross-sectional convenience data from boys seen in a pediatric wellness setting. Also, assessments were not done by pediatric endocrinologists "with more extensive experience in sexual maturity staging." Also, height and weight equipment could not be calibrated because of the large number of participating centers.

But the authors pointed out that previous studies on boys, weight, and puberty have been hampered by small sample sizes, the use of proxy measures of puberty such as timing of the pubertal growth spurt versus Tanner stage, and the lack of multiple measures of puberty.

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