Intermittent fasting proves effective for adolescent obesity

Intermittent energy restriction (IER), already popular in adults in forms such as the 5:2 diet, may be a useful option in helping obese adolescents manage their weight, Australian research suggests.

A study of 12-17 year-olds with a median BMI of 34.9 at The Westmead Children’s Hospital found IER was acceptable to young people and led to improvements in BMI and measures of cardiovascular risk.

The teens were started on a very-low-energy diet (VLED) three days per week with food provided, and a prescribed healthy eating plan for the remainder of the week.

After eight weeks, they had to provide their own food but remained on the same protocol of three VLED days per week.

During weeks 13-26 of the uncontrolled study, the adolescents could choose to whether to remain on IER at one, two or three days per week or swap over to just the prescribed healthy eating plan. Most (23 of 30 teens) elected to continue with IER.

Participants were also supported with face-to-face visits through the study period and phone, email or SMS support.

The study found significant improvements in BMI at 12 weeks, with reductions in BMI %95 percentile of 5%, which  were maintained at 26 weeks. Waist to height ratio also reduced at 12 weeks and body fat percentage reduced between 12 and 26 weeks.

The amount of weight loss appeared sufficient to kickstart metabolic change.

Plasma triglycerides were significantly reduced at 26 weeks compared to baseline (-0.33 mmol/L) however other lipids and blood pressure were unchanged. Fasting blood glucose levels increased.

Arterial wall thickness and endothelial function improved between baseline and 12 weeks and in the case of arterial wall thickness was maintained at 26 weeks.

Dietary adherence was good with adolescents reporting more dietary restraint and less emotional eating over the study period.

Participants reported the main challenge was going out with friends while on the diet but most were able to swap VLED days to accommodate school, social and family events. Most felt the diet could be maintained long term.

“Findings from this study support our hypothesis that IER is an effective dietary intervention which can lead to reductions in BMI and cardiometabolic risk,” the study authors wrote in the Journal of Nutrition.

“Adolescents also reported that the dietary plan was acceptable, appreciating the relative flexibility that IER provides. Together these results add to the adult literature on the use of IER, indicating that it may be an alternative eating plan for adolescents with obesity.”

Senior author and dietician Associate Professor Sarah Garnett told the limbic adolescents liked the way they could fit the IER into their family and social lives however it may not be for everyone.

“This is just one dietary intervention. It’s often something the adolescents are quite interested in because it’s had a huge amount of publicity with the 5:2 diet and Michael Mosley,” she said.

Those who withdrew from the study were typically more obese and reported reduced general wellbeing compared to study completers.

She added that such a program would ideally be done under the supervision of a dietician to check the ongoing nutritional adequacy of the diet.


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