Obesity in childhood is linked to the lowering age of puberty, according to a recent study.

Researchers from Plymouth University Peninsula Schools of Medicine and Dentistry found that a child who is heavier at age five tends to have lower levels of a protein called sex hormone-binding globulin - a hormone whose levels are initially high in childhood but decline significantly before puberty, in essence 'allowing' puberty to happen --throughout childhood and reaches puberty sooner. The tendency was more striking in girls than in boys.

"Here we have found compelling evidence that hormonal effects of obesity, and associated inflammation, affect levels of SHBG and hence the age when puberty commences," researcher Jonathan Pinkney said in a statement. "As a higher proportion of youngsters around the world have become obese, so has the age of puberty dropped. We now know that the relation between these issues is more than coincidental."

For the study, researchers analyzed data from the Earlybird longitudinal measurement of 347 schoolchildren in Plymouth, UK, aged five to 15 years.

Their findings suggested that a combination of hormonal disturbances that are associated with weight gain and obesity, together with inflammation, might be the biological mechanism that explains the observed relationship between weight gain and the declining age of puberty.

Researchers said they do not know what increasing body weight is associated with early puberty, especially in girls, but one possible explanation for this is that humans, like all mammals, require large amounts of energy to reproduce. Throughout most of evolution, "a well-nourished state would have greatly favored successful pregnancy in a world with high perinatal mortality. Conversely, a state of poor nutrition and low body weight, is disadvantageous to reproduction, and slows down reproductive maturation or leads to infertility," researchers said in the study.

"These findings have significant implications for children's development and public health around the world. Reduction in the age of puberty, as a result of early weight gain, expedites physical and psychosocial development at a younger age, and this potentially means an earlier ability to reproduce as well as poorer long term adult health. The observed effects on puberty are another reason to take action against childhood obesity," Pinkney said.

The findings were recently published in the Journal of Clinical Endocrinology and Metabolism.