The proportion of teenagers who are overweight or obese has risen over the past 30 years. In parallel, there has been an increase in societal focus on weight loss and dieting – namely in the form of “anti-obesity” public health campaigns, the expansion of the weight-loss and fitness industry, and weight-focused media content – from TV shows to social media trends. We know that these messages have not translated in a decrease in the prevalence of obesity, which has remained relatively stable over the past 15 years. However, what we don’t know is whether dieting behaviours and weight concerns have increased – and what impact this might have had on teenagers’ mental health.
Our study found that teenagers born in 2000-2002 (often called “Generation Z”) are more concerned about their weight and losing weight than previous generations. We also found that Gen Z teenagers who dieted and thought of themselves as being overweight had greater symptoms of depression than those who did in previous generations.
Dieting and exercise
To conduct our study, we used data from 22,503 adolescents who took part in three large UK general population cohorts. 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 participants were aged 14-16, these studies collected information on weight loss behaviours and weight perception in early adolescence.
We found that compared to teenagers from 1986 and 2005, more teens in 2015 were trying (or had tried) to lose weight by dieting or exercising, or described themselves as overweight. Although these behaviours were more common in girls, their prevalence increased more in boys over these 30 years.
We also observed that more teens in this generation were exercising to lose weight. This is interesting, because we know from other research that the proportion of young people engaging in physical activity has remained relatively stable. So although today’s teens aren’t necessarily exercising more than past generations, our findings suggest that teens today are increasingly exercising with the aim of losing or controlling their weight.
Finally, we found that adolescents who were trying to lose weight or described themselves as overweight had greater symptoms of depression. For girls in particular, these symptoms have become more severe in Gen Z compared to prior generations.
Crucially though, none of the differences that we observed in this study were explained by higher BMI in the more recent cohorts.
It’s well known that pressures to lose weight and weight stigma are associated with increased risk of body dissatisfaction and dieting. Our study adds to existing evidence that making weight loss the main focus of public health campaigns might create more harm than good by increasing mental health problems in teenagers.
Public health campaigns aimed at reducing the prevalence of obesity often focus on calorie labelling and exercise as means to achieve or maintain a healthy weight. Yet evidence suggests that dieting is ineffective for long-term weight loss.
Obesity is also known to be influenced by a number of social determinants such as being from a socio-economically disadvantaged background. Framing weight loss as a personal responsibility, as it has been done so far, is therefore not only ineffective, but also dangerous. Pressures to lose weight can lead to internalising weight stigma, body dissatisfaction, and disordered eating behaviours, all known to increase mental health as well as physical health problems.
Praising young people for weight loss or showing concerns for them depending on their BMI ignores the fact that disordered eating behaviours and body dissatisfaction are associated with negative mental health outcomes at all levels of BMI, which is what we observed in our study.
It’s therefore crucial that good physical and mental health are promoted above healthy weight and weight loss – and that children are taught to enjoy exercise as a time to learn new skills, and spend time with friends, as opposed to as justification for eating. It will also be important for anti-obesity campaigns to consider how they can prevent adverse mental health outcomes or disordered eating when they’re designed.