A 52-week randomized clinical trial found that intermittent energy restriction produced comparable weight loss and cardiometabolic improvements to continuous energy restriction in adolescents with obesity-associated complications.
Key findings:
- Both groups achieved significant reductions in BMI z-score at 52 weeks (IER: -0.28; 95% CI, -0.37 to -0.20; CER: -0.28; 95% CI, -0.36 to -0.20)
- No significant differences were found between groups in body composition or cardiometabolic outcomes
- Insulin resistance improved in both groups at 16 weeks but was maintained only in the CER group at 52 weeks
- More participants withdrew from the IER group (28/71, 39.4%) compared to CER (16/70, 22.9%)
The study was conducted from 2018 to 2023 at two tertiary pediatric centers in Australia. Participants had a median age of 14.8 years, and 50.4% were male. Inclusion criteria required obesity (BMI ≥30) and at least one cardiometabolic complication such as prediabetes, insulin resistance, or dyslipidemia.
Baseline characteristics of the study population included:
- Mean weight: 100.42 kg (SD 16.50)
- Mean BMI: 35.39 (SD 4.17)
- Mean waist circumference: 107.45 cm (SD 11.61)
- Mean body fat percentage: 46.09% (SD 5.23)
- Family history of obesity: 68.8%
- Family history of diabetes: 83.0%
- Participants taking metformin: 14.2%
Demographic data showed that 82.9% were born in Australia, 47.5% reported one or both parents not born in Australia, and 40.4% reported speaking a language other than English at home. Additionally, 1.4% identified as Aboriginal or Torres Strait Islander.
The cardiometabolic profile at baseline revealed:
- Mean systolic blood pressure: 119.5 mm Hg (SD 10.5)
- Mean diastolic blood pressure: 68.1 mm Hg (SD 9.3)
- Median total cholesterol: 166 mg/dL (95% CI 166-178)
- Median HDL-C: 42 mg/dL (95% CI 42-46)
- Median LDL-C: 112 mg/dL (95% CI 112-124)
- Median triglycerides: 115 mg/dL (95% CI 115-133)
- Median fasting glucose: 88 mg/dL (95% CI 88-90)
- Median insulin: 22 μIU/mL (95% CI 23-29)
Prevalence of cardiometabolic complications at baseline included:
- Dyslipidemia: 42.6%
- Elevated liver enzymes: 27.0%
- Insulin resistance: 81.6%
- Elevated fasting glucose (100.90-124.32 mg/dL): 8.0%
Intervention details:
- Phase 1 (weeks 0-4): All participants followed a 3350 kJ/d (800 kcal/d) very low-energy diet using meal replacements
- Phase 2 (weeks 5-16):
- IER group: 2500-2950 kJ (600-700 kcal) 3 days/week alternating with 4 days of healthy eating
- CER group: Daily energy prescription of 6000-8000 kJ/d (1430-1900 kcal/d) based on age
- Phase 3 (weeks 17-52): Continued assigned diet or transitioned to weight maintenance if goal weight achieved
Intervention adherence data showed that 75.2% of participants attended > 9 scheduled visits, with no significant difference in dietitian attendance between groups.
Results at 52 weeks included:
- BMI reduction: IER -1.62 (95% CI, -2.39 to -0.85); CER -1.53 (95% CI, -2.25 to -0.81)
- Fat mass index reduction: IER -1.59 (95% CI, -2.36 to -0.83); CER -1.45 (95% CI, -2.12 to -0.79)
- 5% BMI95 reduction: 35.0% IER vs 27.8% CER
- 10% BMI95 reduction: 15.0% IER vs 14.8% CER
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15% BMI95 reduction: 17.5% IER vs 18.5% CER
Estimated marginal mean change in BMI95 was -9.56 (95% CI, -12.36 to -6.83) for IER and -9.23 (95% CI, -11.82 to -6.64) for CER. Waist circumference reduction at 52 weeks was -3.77 cm for IER and -3.26 cm for CER.
Body composition changes showed a fat-free mass index change at 52 weeks of +0.13 (95% CI, -0.19 to 0.44) for IER and -0.05 (95% CI, -0.33 to 0.22) for CER.
Blood pressure outcomes revealed that 27.7% had persistent elevated blood pressure, 24.4% had resolution of elevated blood pressure, 10.0% developed elevated blood pressure, and 37.7% maintained normal blood pressure throughout the study.
Adverse events were reported in 47.5% of participants, with 96 total events occurring in 67 participants. In the IER group, 13 participants had 1 event and 10 had 2-6 events, while in the CER group, 21 participants had 1 event and 12 had 2-5 events. Eight serious adverse events occurred across 6 participants, with two possibly related to the intervention. Two participants were withdrawn due to mental health concerns.
The study faced limitations due to the COVID-19 pandemic, with 35.5% of participants enrolled before 2019 and completing before the pandemic, while 49.6% were recruited after 2020. Recruitment was extended by 2 years due to pandemic-related delays.
The findings suggested that IER may be a viable alternative to CER in adolescent weight management programs, offering similar improvements in weight and cardiometabolic outcomes over a 52-week period.
Conflict of interest disclosures can be found in the study.