A review of more than 100 studies revealed that girls who are overweight tend to reach puberty earlier than their peers do.

While some researchers have argued attaining puberty early in life makes a person prone to metabolic syndrome and diabetes and Emily Walvoord has found such diseases are not linked to early puberty, but obesity.

Walvoord of Indiana University School of Medicine said that early puberty is one of the many outcomes of obesity and there are clearly other factors that have affected the timing

While childhood obesity is a growing epidemic, she suggested other factors include a possible increase in hormone-disrupting chemicals in the environment and more chronic stress in children’s home.

She said many unanswered questions exist, none more troubling than that of the psychological impact. The long-term effect on adolescents is still not clear. Girls who reach puberty early are more likely to experience negative body image, depression and other mental disorders.

Jane Mendle of University of Oregon said those in her field know the psychological effects of early puberty well. Mendle said girls who mature earlier tend to land in social situations they are not psychologically prepared to handle and due to this reason, they might develop psychological issues during puberty.

However, those mental health issues are associated closely with obesity, so it is difficult to straighten out the cause and effect relationship.

While research on boys and puberty is less compared to girls, researchers of this study believe that the duration of puberty is the deciding factor whether puberty has an emotional influence or not on its onset as in case of girls.