Some 21% of obese 13-year-olds in Ireland consider themselves to be the right size or very/a bit skinny, a new report has found.

According to the latest report from the Growing Up in Ireland study, the findings suggest ‘a certain level of misperception' when it comes to how young teens view their own weight status.

Growing Up in Ireland: The National Longitudinal Study of Children has been monitoring the development of nearly 20,000 children since 2007 - over 11,000 children who were nine-month-olds at the outset and more than 8,500 children who were nine-year-olds. It is carried out by the Economic & Social Research Institute (ESRI).

This latest report is based on interviews with over 7,400 young people and their families when the children were 13 years old in 2012 and when they were 9 years old in 2007/08.

It found that most 13-year-olds were in good physical health, however 20% were overweight and 6% were obese.

Girls were more likely to be overweight or obese than boys, and girls were also less likely to take part in physical exercise than boys.

Children from lower social classes were also more likely to be overweight or obese, and were also less likely to participate in physical activity and organised sport.

Meanwhile, the report noted that the weight status of children at the age of nine was a good indicator of their weight status at the age of 13. If weight problems were established earlier in childhood, they were difficult, although not impossible, to reverse.

However, by the age of 13, there was a degree of misperception, with 21% of obese 13-year-olds considering themselves ‘just the right size' or ‘very/a bit skinny'.

When it came to families and emotional wellbeing, most 13-year-olds were living in two-parent families and had a good relationship with their parents. However, those from one-parent families and from families in which their mother had lower levels of education were more at risk of experiencing emotional and behavioural problems.

Children appeared to be at an increased risk of experiencing emotional and behavioural problems if their parents had separated when they were between nine and 13 years of age.

When it came to friendship, 37% said they had between three and five friends, while 35% said they had between six and nine friends. In most cases, parents had met all of their child's friends.

Around 10% of the 13-year-olds said they had been bullied, while 2% said they had bullied someone else. Those who had been bullied were, not surprisingly, at an increased risk of experiencing emotional and behavioural problems.

The report also revealed that 9% of 13-year-olds had tried smoking and levels were higher among those from poorer backgrounds. Some 16% had tried alcohol, 3% had tried sniffing glue, while 1% had tried cannabis.

Commenting on the launch of the report, Prof James Williams of the ESRI, said that it highlights some of the key issues relating to this key time in a young person's life, ‘as they face into the many challenges posed by their teenage years'.

"It also underlines the invaluable input which the Growing Up in Ireland project can make to developing policies and interventions to support all young people growing up in modern Ireland," he noted.

Also commenting on the launch, the Minister for Children and Youth Affairs, Dr Katherine Zappone, said that the report ‘serves to remind us how developmental trends evident at 13 are often evident earlier in childhood and can be difficult to reverse'.

"This new data is invaluable and it reinforces our efforts to intervene well and to intervene early, so that we can ensure positive outcomes for all children," she added.