Public health campaigns may be responsible for rising weight concerns and mental health issues in teenagers.
The findings come from a new study led by University College London, which analysed data from 22,503 UK adolescents born between 1970 and 2015.
Study participants were asked questions about their dieting and exercise habits, as well as their perception of their own weight. They also filled out questionnaires in order to gauge depressive symptoms.
According to the study, rates of weight misperception and weight-related behaviours in teenagers have steadily increased across generations, with 4 in 10 teenagers reporting weight loss attempts in 2015 – up from 3 in 10 in 2005.
Rates of dieting and exercising to lose weight were also at their highest in 2015 at 44% and 60% respectively, compared with 38% and 7% in 1986.
Girls were found to consistently be more likely to diet to lose weight, but rates among boys had increased as well, along with an increasing desire to gain weight.
"Our findings show how the way we talk about weight, health and appearance can have profound impacts on young people's mental health, and efforts to tackle rising obesity rates may have unintended consequences," said lead study author, Dr Francesca Solmi.
"An increase in dieting among young people is concerning because experimental studies have found that dieting is generally ineffective in the long term at reducing body weight in adolescents, but can instead have greater impacts on mental health. We know, for instance, that dieting is a strong risk factor in the development of eating disorders."
Regarding weight perception, the likelihood for both boys and girls to over-estimate their weight increased between 1986 and 2005, and again between 2005 and 2015, highlighting concerns that increased efforts to lose weight were not necessarily due to increased obesity rates.
An association between depressive symptoms and weight-related behaviours and weight misperception was also reported, with this relationship growing stronger in girls over the three decades.
Dr Solmi added: "Media portrayals of thinness, the rise of the fitness industry and the advent of social media may all partly explain our results, and public health messaging around calorie restriction and exercise might also be causing unintended harm.
"Public health campaigns around obesity should consider adverse mental health effects, and ensure they avoid weight stigma. By promoting health and wellbeing, as opposed to focusing on 'healthy weight', they could have positive effects on both mental and physical health."
A shift in mindset toward exercising was also highlighted in the study, with a growing number of young people seemingly doing so to lose weight rather than for fun, socialising or feeling healthy.
Interestingly, a recent study commissioned by AXA Health actually reported a growing movement toward more enjoyable ways to exercise, shifting away from strenuous 'no pain, no gain' alternatives.
To read the full study, click here.