Intermittent fasting matches calorie restriction for weight loss in teens living with obesity

Intermittent fasting is just as effective as traditional calorie restriction for weight loss in teenagers with obesity, according to a new Australian study.

The findings, published in JAMA Pediatrics, suggest that both dietary methods can also improve underlying mental health issues such as depression and disordered eating.

The randomised clinical trial, known as the Fast Track to Health trial, followed 141 adolescents aged 13 to 17 living with obesity over the course of 52 weeks. It found that both intermittent energy restriction (IER) and continuous energy restriction (CER) led to significant reductions in body mass index (BMI) and improvements in cardiometabolic health.

By the end of the year-long study, both diet approaches resulted in a similar reduction in BMI, with IER leading to a drop of 1.62 and CER achieving a 1.53-point decrease. Additionally, around one-third of the teens in both groups reached a five per cent reduction in BMI.

"This is the first randomised clinical trial to evaluate intermittent fasting in adolescents, and the findings provide teens with more choice beyond traditional calorie restriction," said lead researcher Dr. Natalie Lister from the University of Sydney. "In Australia, there are limited treatment options for adolescents living with obesity, and this study offers another viable pathway."

The trial also explored the impact of these diets on mental health. Both intermittent fasting and calorie restriction were associated with reductions in self-reported depression and eating disorder symptoms. Interestingly, the intermittent fasting group showed longer-lasting improvements in binge eating compared to the calorie-restriction group.

Of the participants, 17 adolescents (12.1 per cent) required additional support for mental health concerns during the trial, with two individuals being withdrawn due to serious mental health-related adverse events. One teen developed atypical anorexia nervosa after rapid weight loss and restrictive behaviors, while another experienced a resurgence of prior body image issues.

Dr. Lister highlighted the importance of ongoing support for adolescents, noting that dietary interventions, while effective, must be carefully managed. "Doctors should be aware that adolescents with high weight may present with cardiometabolic complications usually seen in adults. Continuous support from a dietitian is essential to improve both weight and cardiometabolic health."

The study found significant reductions in insulin resistance for both diet groups at week 16, with continued improvement in the calorie-restriction group by week 52. Other health markers, such as dyslipidemia and liver function, also improved in both groups.

While the study shows promise, the researchers stress the need for further long-term data beyond the 12-month intervention period to fully understand the clinical implications of these diets.