The negative effects of bullying are already known to reach far into adulthood, but a new study published in the journal Psychosomatic Medicine suggests that it might even affect our waistlines.

First, researchers studied data from an older, long-running study including over 2,000 twin children born in the UK from 1994 to 1995. The children were tracked from birth until they were 18 years old, allowing the researchers to compare rates of becoming obese and overweight (via measurements of body mass index, or BMI) among children who reported being bullied and those who hadn’t. They found that children who had been bullied over a long period of time, meaning they were chronically bullied during elementary and middle school, were 70 percent more likely to be overweight at age 18 than their non-bullied counterparts. Though bullied children were more likely to come from a struggling home or have mental health issues, the connection between bullying and weight continue to exist after accounting for these and other factors, such as genetic history.

“Bullying is commonly associated with mental health problems, but there is little research examining the physical health of bullied children,” said senior author Dr. Andrea Danese of King's College London in a statement. “Our study shows that bullied children are more likely to be overweight as young adults, and that they become overweight independent of their genetic liability and after experiencing victimization.”

Overall, 20 percent of non-bullied children became overweight by the age of 18, compared to 29 percent of chronically bullied children. Children who were only bullied in elementary school were also more likely to become overweight, but not to the same degree. That further suggests that bullying itself can directly raise the risk of becoming overweight, the researchers said. Bullied children overall were also more likely to have a higher waist-hip ratio, another measurement of obesity.

Previously, the researchers had studied children born in the 1960s and found a similar connection between bullying and weight by the time they reached their 40s. This time, they were also able to account for known genetic factors of obesity while studying children born in an era when rates of obesity have greatly risen.

“Although we cannot definitively say that bullying victimization causes individuals to become overweight,” explained the study's lead author Jesse Baldwin, a research student at King’s College, “ruling out alternative explanations, such as genetic liability, strengthens the likelihood that this is the case.”

Baldwin and her colleagues now hope their research can further highlight the importance of protecting children from bullying.

“As well as preventing bullying, our findings emphasize the importance of supporting bullied children to prevent them from becoming overweight, which could include interventions aimed at promoting exercise and healthy eating,” Baldwin said. “Our data suggest that such interventions should start early in life.”

Source: Baldwin J, Arseneault L, Odgers C, et al. Childhood Bullying Victimization and Overweight in Young Adulthood: A Cohort Study. Psychosomatic Medicine. 2016.