Intermittent Energy Restriction for Adolescents With Obesity: The Fast Track to Health Randomized Clinical Trial.

IMPORTANCE

Adolescent obesity requires effective and accessible treatment. Intensive dietary interventions have the potential to be used as adjunctive therapy for behavioral weight management.

OBJECTIVE

To examine the effectiveness of 2 diet therapies, delivered as part of an intensive behavioral weight management intervention, in adolescents with metabolic complications associated with obesity.

DESIGN, SETTING, AND PARTICIPANTS

This multisite, 52-week randomized clinical trial was conducted from January 31, 2018, to March 31, 2023, at 2 tertiary pediatric centers in Australia. Adolescents (aged 13-17 years) with obesity and 1 or more associated complications were included.

INTERVENTIONS

Intensive behavioral interventions, delivered by a multidisciplinary team, comparing intermittent energy restriction (IER) or continuous energy restriction (CER), with 3 phases: very low-energy diet (weeks 0-4), intensive intervention (weeks 5-16), and continued intervention and/or maintenance (weeks 17-52).

MAIN OUTCOMES AND MEASURES

The primary outcome was body mass index (BMI) z score at 52 weeks in the IER vs CER group. Anthropometry, body composition, and cardiometabolic health were assessed at baseline and 52 weeks. The BMI z score and percentiles were determined using Centers for Disease Control and Prevention growth charts. Insulin resistance, dyslipidemia, and elevated hepatic function were assessed.

RESULTS

A total of 141 adolescents (median [IQR] age, 14.8 [12.9-17.9] years; 71 male [50.4%]) were enrolled, 71 in the IER group and 70 in the CER group, and 97 (68.8%) completed the intervention, 43 in the IER group and 54 in the CER group. At week 52, both groups had reduced BMI z scores (estimated marginal mean change, -0.28 [95% CI, -0.37 to -0.20] for IER and -0.28 [95% CI, -0.36 to -0.20] for CER) and reduced BMI expressed as a percentage of the 95th percentile (estimated marginal mean change, -9.56 [95% CI, -12.36 to -6.83] for IER and -9.23 [95% CI, -11.82 to -6.64] for CER). No differences were found in body composition or cardiometabolic outcomes between the groups. Both groups had a reduction in the occurrence of insulin resistance (from 52 of 68 [76.5%] to 32 of 56 [57.1%] in the IER group and from 59 of 68 [86.8%] to 31 of 60 [57.1%] in the CER group) at week 16; however, at week 52, this effect was observed in the CER group only (from 59 of 68 [86.7%] to 30 of 49 [61.2%]). The occurrence of dyslipidemia was unchanged between baseline and week 52 (60 of 137 [42.6%] and 37 of 87 [42.5%], respectively), with a small improvement in occurrence of impaired hepatic function tests (37 of 139 [27.0%] and 15 of 87 [17.2%], respectively). No differences were found in dyslipidemia or hepatic function between groups.

CONCLUSIONS AND RELEVANCE

These findings suggest that for adolescents with obesity-associated complications, IER can be incorporated into a behavioral weight management program, providing an option in addition to CER and offering participants more choice.

TRIAL REGISTRATION

http://anzctr.org.au Identifier: ACTRN12617001630303.