While girls who mature sexually at an early age are more likely to be obese, researchers at the University of Illinois at Chicago report that boys who mature early are less likely to be obese.

Although previous studies have suggested that sexual maturity is linked with obesity in girls, not much was known about how sexual maturity affected boys and their weight.

The gender differences seen in the study between sexual maturity and obesity may be related to differences in biological development, said Dr. Youfa Wang, assistant professor of human nutrition and author of the study published in the journal Pediatrics. In boys, early developers were found to be significantly taller but not heavier than average or late-maturing boys. However, early sexual maturity in girls was linked with both an increase in height and weight.

"This suggests that sexual maturity might have different biological influences on growth in weight and height in boys and girls," said Wang. "During the growth process in boys, more energy may be devoted toward height than to the development of fat tissue, while early-maturing girls are more likely to store extra energy intake as fat tissue."

Researchers looked at childhood obesity by assessing body stature and early sexual maturation in 1,501 boys and 1,520 girls ages 8 to 14 who participated in the Third National Health and Nutrition Examination Survey from 1988 to 1994. Younger and older children were not considered in the analysis.

The children were considered "early maturers" if they reached a certain stage of sexual development earlier than other children in the study. Adjustments were made for age, ethnicity, residence, family income, diet and physical activity.

There is a need for further study into the casual relationship between the timing of sexual maturation and development of obesity as well as the influence of behavioral, social and environmental factors on gender differences, said Wang.

Wang believes further understanding of the link between sexual maturity and obesity has important clinical implications. "It can help refine and develop appropriate measurement references, and it can help guide us in employing more effective methods and resources used in preventing and managing childhood and adolescent obesity."

Other sources: University of Illinois at Chicago