Steinsbekk is the first author of a study from NTNU, investigated how children with high BMI perceive their own body size. The results have now been published in the journal Frontiers in Psychology.

"To put it simply, first we have to acknowledge that we have a problem before we can do something about it. This also applies to parents: if they don't recognize that their children have a weight problem, they won't seek help for it," said Associate Professor Silje Steinsbekk 

The study is based on data from the Norwegian research project Tidlig Trygg i Trondheim, a longitudinal population-based study that looks at the risk and protective factors contributing to children's psychological and social health.

The project has followed up with nearly a 1000 children and their parents every other year since the children were four years old. Researchers are also studying what factors promote good health habits and what contributes to the development of obesity, inactivity and poor eating habits.

"We investigated how the children estimated their own body size and compared this to how their estimates changed from age 6 to 8 and age 8 to 10. We also looked at what could explain the developments," said Steinsbekk.

The children were shown 7 pictures of girls and boys with known BMI and asked which picture looked the most like them. The researchers then calculated the difference in BMI between the figure identified by the children and the children's own BMI based on measured height and weight.

"That way, we got a measure of how big the difference between actual body size and estimated body size was", said Steinsbekk. It is important to note that age and gender need to be taken into account when assessing whether children are overweight or obese.

Biggest children underestimated the most often. Generally, the researchers found that children more often underestimated than overestimated the size of their body, although the majority made accurate estimates. Boys were more likely to underestimate their own body size than girls.

Steinsbekk said "We also found that the higher the children's BMI, the more they underestimated their size over time." The largest children thus underestimated their body size the most and showed an increased degree of underestimation over time (that is, from 6 to 8 and from 8 to 10 years old). 

However, this can have some advantages. "It is reasonable to imagine that underestimating protects you from acknowledging that your body is bigger than you want, and that can be quite practical," said Steinsbekk.

"Denial may be a favorable defense mechanism, but it can also be an obstacle to making necessary changes," said Steinsbekk. "For children, the parents' acknowledgment of the problem is what's most important. Parents are the ones who need to make the necessary adjustments to promote good health."