The proportion of overweight or obese teenagers has increased past 30 years.
At the same time, there is an increasing social focus on weight loss and diets – namely in the form of Public health campaigns against obesity, weight loss extension and fitness industry, and weight-oriented media content – from tv shows to trends on social media.
We know these messages have not translated into a decrease in obesity prevalence, which has remained relative stable in the past 15 years.
What we don’t know, however, is whether diet habits and weight concerns have increased – and what impact this may have had on teens’ mental health.
Our study found that teens born in 2000-2002 (often referred to as “Generation Z”) are more concerned about their weight and weight loss than previous generations.
We also found that Gen Z teens who dieted and thought they were overweight had more symptoms of depression than those who did in previous generations.
Diet and exercise
To conduct our study, we used data from 22,503 adolescents enrolled in three large UK cohorts of the general population.
This included the British Cohort Study of people born in 1970, the Avon Longitudinal Study of Parents and Children, which looked at children born in 1991-92, and the Millennium Cohort Study of children born in 2000-2002.
In 1986, 2005 and 2015, when the participants were 14-16 years old, these studies collected information about weight loss behavior and weight perception in early adolescence.
We found that compared to teens from 1986 and 2005, more teens in 2015 were trying (or had attempted) to lose weight by dieting or exercising, or describing themselves as overweight.
Although this behavior was more common in girls, their prevalence increased more in boys during these 30 years.
We also saw that more teens in this generation are training to lose weight.
This is interesting because we know about it other research that the proportion of young people who engage in physical activity has remained relatively stable.
So while today’s teens don’t necessarily exercise more than previous generations, our findings suggest that teens today are increasingly exercising with the goal of losing or controlling their weight.
Finally, we found that adolescents who tried to lose weight or described themselves as overweight had more symptoms of depression. Especially for girls, these symptoms have become more severe in Gen Z compared to previous generations.
Crucially, however, none of the differences we saw in this study were explained by higher BMI in the more recent cohorts.
Pressure to lose weight and weight stigma are known to be associated with an increased risk of diabetes dissatisfaction with the body and diets.
Our study adds to the existing evidence that weight loss may be the main focus of public health campaigns, causing more harm than good by increasing mental health problems in teens.
Public health campaigns aimed at reducing the prevalence of obesity often target calorie labeling and exercise as a means of achieving or maintaining a healthy weight. Still, there is some evidence that dieting is not effective for long term weight loss.
Obesity is also known to be affected by some social determinants such as coming from a socio-economically disadvantaged background.
Taking weight loss as a personal responsibility, as it has been done so far, is therefore not only ineffective, but also dangerous.
Praising young people for weight loss or showing concern for them, depending on their BMI, ignores the fact that disordered eating behavior and dissatisfaction with the body are associated with negative mental health outcomes at all BMI levels, which we observed in our study.
It is therefore critical that good physical and mental health is promoted over healthy weight and weight loss – and that children are taught to enjoy exercise as a time to learn new skills and to spend time with friends, rather than as a justification to eat.
For anti-obesity campaigns, it will also be important to think about how they can prevent adverse mental health effects or disturbed eating when designed.