Children as young as ten are making themselves vomit in order to lose weight and the problem is more common in boys than girls, according to a study of nearly 16,000 school pupils published online early, ahead of print publication, by the Journal of Clinical Nursing.
The findings have prompted researchers to issue a warning that self-induced vomiting is an early sign that children could develop eating disorders and serious psychological problems, such as binge eating and anorexia.
They also believe that self-induced vomiting can be tackled by making sure that children get enough sleep, eat breakfast every day, eat less fried food and night-time snacks and spend less time in front of a computer.
Thirteen per cent of the 8,673 girls and 7,043 boys who took part in the research admitted they made themselves sick to lose weight. But the figures were much higher in younger children, with 16% of 10-12 year-olds and 15% of 13-15 year-olds vomiting. The figures fell to 8% in 16-18 year-olds.
The study of 120 schools, carried out for Taiwan's Ministry of Education, also found that 16% of the boys made themselves sick, compared with 10% of the girls.
"Our study, which was part of a wider research project on health and growth, focused on children who said that they had tried to lose weight in the last year" says lead author Dr Yiing Mei Liou, Director of Clinical Practice of the School of Nursing at National Yang-Ming University, Taiwan.
"It showed that self-induced vomiting was most prevalent in adolescents who had a sedentary lifestyle, slept less and ate unhealthily.
"Obesity is a growing problem in industrialised countries and is an increasingly important medical, psychosocial and economic issue. It's estimated that obesity among children and teenagers has nearly tripled over the last three decades and international studies have revealed worrying trends.
"For example, a study by the US Centers for Disease Control and Prevention, published in 2010, found that 4% of students had vomited or taken laxatives in the last 30 days to lose or stop gaining weight. And a South Australian study published in 2008 said that eating disorders had doubled in the last decade."
The Taiwan study found that 18% of the underweight children used vomiting as a weight-loss strategy, compared with 17% of obese children and 14% of overweight children. Normal weight children were least likely to vomit (12%).
A number of factors were associated with high levels of self-induced vomiting. For example, more than 21% of the children who vomited ate fried food every day, 19% ate desserts every day, 18% ate night-time snacks every day and 18% used a computer screen for more than two hours a day.
When the researchers carried out an odds ratio analysis, they found that using a computer screen for more than two hours a day increased the vomiting risk by 55%, eating fried food every day by 110% and having night-time snacks every day by 51%. They also found that children were less likely to make themselves sick if they slept more than eight hours a night and ate breakfast every day.
"Our study found that children as young as ten were aware of the importance of weight control, but used vomiting to control their weight" concludes Dr Liou. "This reinforces the need for public health campaigns that stress the negative impact that vomiting can have on their health and encourage them to tackle any weight issues in a healthy and responsible way.
"The findings also suggest that self-induced vomiting might serve as an early marker for the development of obesity and/or other eating and weight-related problems."
Prevalence and correlates of self-induced vomiting as weight-control strategy among adolescents in Taiwan. Liou et al. Journal of Clinical Nursing. Online early ahead of print publication. (June 2011). DOI: 10.1111/j.1365-2702.2011.03739.x