The shifting trends in body weight perception, where fewer people now perceive themselves as overweight, could reduce the effectiveness of public health interventions aimed at tackling obesity, finds a study.

The study involving more than 745,000 adolescents from 41 countries across Europe and North America identified an increase in the number of teenagers who underestimate their body weight, making them feel it unnecessary to lose excess weight and lead a healthy life.

The findings, published in the journal Child and Adolescent Obesity, also demonstrated a noticeable decrease in those who overestimate their weight.

"During this impressionable age, body weight perception may influence a young person's lifestyle choices, such as the amount and types of food they eat and their exercise habits," said lead author Anouk Geraets, from the Department of Social Sciences, at the University of Luxembourg.

"So it's concerning that we're seeing a trend where fewer adolescents perceive themselves as being overweight -- as this could undermine ongoing efforts to tackle increasing levels of obesity in this age group. Young people who underestimate their weight and therefore do not consider themselves to be overweight may not feel they need to lose excess weight and, as a result, they may make unhealthy lifestyle choices," Geraets said.

A person's perception of their body weight may not accurately reflect their actual weight. A discrepancy in body weight perception (BWP) may either be an underestimation (where actual weight is higher than perceived weight) or an overestimation (where actual weight is lower than perceived weight).

In the study, the researchers found underestimation of weight status increased, and overestimation of weight status decreased over time among both sexes, with stronger trends for girls. Correct weight perception increased over time among girls, while it decreased among boys.

The team stated that the increased underestimation and decreased overestimation of weight status over time for girls may be explained by the emergence of an athletic and strong body, as a new contemporary body ideal for both sexes.

"This study has clinical and public health implications. The increase in correct weight perception and the decrease in overestimation may have a positive effect on unnecessary and unhealthy weight loss behaviours among adolescents, while the increase in underestimation might indicate the need for interventions to strengthen correct weight perception," Geraets said.