Materials and Methods The study will compare the effect of 4000 IU vitamin D
supplementation over six months on adipokines (leptin/adiponectin ratio) and insulin
resistance (HOMA index) in school-aged children and adolescents with obesity, against a
similar group receiving 1000 IU of vitamin D. The study will be conducted at the Hospital
Infantil de México Federico Gómez and UMAE Hospital de Pediatría, Centro Médico Nacional
Siglo XXI. This controlled clinical trial features an experimental, randomized,
double-blind design. The study population includes schoolchildren with obesity attending
the Adolescent Clinic at Hospital Infantil de México and outpatient services at UMAE
Hospital de Pediatría.
Sampling and Selection Criteria A non-probabilistic sampling will select children
identified with obesity. Selection criteria include both male and female patients aged 10
to 18 with obesity as per BMI (>95th percentile according to WHO age and sex tables), who
agree to participate, and reside in Mexico City. Exclusion criteria exclude patients with
comorbidities unrelated to obesity, genetic syndromes, those currently receiving vitamin
supplements or pharmacological treatments for obesity, and those with pre-existing
insulin resistance requiring pharmacological treatment.
Treatment Arms Group A will receive 4000 IU of vitamin D daily for six months. Group B,
the control group, will receive 1000 IU daily. Randomization is managed using a software
tool, with treatment assignments sealed in opaque envelopes and administered according to
randomized allocation.
Sample Size and Statistical Analysis Sample size calculations for unpaired group
comparisons anticipate 20 participants per group, adjusting for a 20% dropout rate, based
on differences in the leptin/adiponectin ratio and HOMA index. Statistical analyses will
be performed on both an intention-to-treat and per-protocol basis. Descriptive analysis
will evaluate quantitative variables' distribution using the Kolmogorov-Smirnov test to
determine appropriate statistical tests. Comparative analyses will utilize t-tests or
U-Mann Whitney tests for quantitative variables, and chi-squared or Fisher's exact tests
for categorical data. Mixed-effects regression models will assess changes in dependent
variables over time. Analyses will be conducted using Stata version 14.0, with a
confidence level of ≤0.05.
Procedures and Follow-Up Prior to the intervention, patients will undergo comprehensive
assessments including anthropometry and blood tests. Dietary and physical activity plans
will be provided, tailored to each patient's caloric needs and physical capabilities.
Monthly follow-ups will ensure adherence to the supplementation regimen and monitor any
adverse effects. The final assessment will repeat all initial evaluations to assess
changes after six months of treatment.
Blinding and Data Integrity The study ensures blinding for medical staff, patients,
families, and data collectors. The treatment capsules for both groups will be identical
in appearance to maintain blinding integrity throughout the trial.
Study Conclusion The study concludes with a final collection of anthropometric and blood
sample data after six months, which will be analyzed to determine the effectiveness of
vitamin D supplementation on improving insulin resistance and adipokine levels among
children and adolescents with obesity.
