In 2012, around 21 percent of American teenagers aged 12-19 years were obese.
According to the Centers for Disease Control and Prevention (CDC), around 21 percent of American adolescents aged 12-19 years were obese in 2012, compared with 5 percent in 1980.
While poor diet and lack of physical activity are key contributors to obesity, studies have indicated there may be other factors at play, such as family history of the condition.
Researchers have also suggested that the hormone spexin - believed to be involved in the regulation of the body's energy balance and fat mass - plays a role in obesity; previous studies have identified reduced levels of the hormone among obese adults.
Dr. Seema Kumar, of the Mayo Clinic in Rochester, MN, and senior author of this latest research, notes that their study is the first to investigate the role of spexin among obese teenagers.
5.25 times greater obesity risk for teens with lowest spexin levels
For their cross-sectional study, the researchers analyzed spexin levels in the blood samples of 69 teenagers aged 12-18 years, of whom 51 were obese and 18 were a normal weight.
The teenagers were allocated to one of four groups, dependent on their spexin levels.
The results of the study revealed that obese teenagers had lower levels of spexin than those of normal weight.
Compared with teenagers who had the highest levels of spexin, those with the lowest levels of the hormone were found to have a 5.25 times greater obesity risk.
Previous studies of spexin among adults have identified an association between levels of spexin and fasting blood sugar levels, but no such link was found in this study.
Dr. Kumar says these findings indicate that spexin may be involved in weight gain that begins at an early age.
"It is noteworthy that we see such clear differences in spexin levels between obese and lean adolescents.
Since this is a cross-sectional study, more research is needed to explore the physiological significance of spexin, how it may be involved in the development of childhood obesity and whether it can be used to treat or manage the condition."
Dr. Seema Kumar