# A Mediterranean lifestyle obesity prevention intervention in preschoolers at risk: MELI-POP Study—a randomized controlled trial

## TL;DR

A Mediterranean lifestyle intervention helped reduce body fat in preschool girls at risk of obesity, but not in boys.

## Contribution

First RCT testing a Mediterranean lifestyle intervention in preschoolers at risk of obesity, using detailed body composition measures.

## Key findings

- The intervention significantly reduced BMI and fat mass index in girls but not in boys.
- No significant changes in cardiovascular risk factors were observed between groups.
- Results suggest sex-specific effects of lifestyle interventions on body composition in young children.

## Abstract

This study aimed to determine whether a Mediterranean lifestyle intervention, including diet and physical activity (PA), influences body composition and cardiovascular risk factors in preschoolers at risk of obesity due to family history. A parallel RCT was conducted in three Spanish cities, enrolling 206 children aged 3.0–6.9 years with normal weight or overweight and at least one parent with overweight or obesity. Participants were recruited from health centers, hospitals, and schools, and randomly assigned to either a Mediterranean lifestyle intervention or a control group. The intervention included provision of fish and olive oil, monthly nutrition education, and twice-weekly PA sessions, while the control group received general child health advice unrelated to diet or exercise. After 12 months, 170 children completed the study (17.5% dropout). Outcomes included BMI, fat mass index (FMI), and respective z-scores (primary), as well as waist-to-height ratio, blood pressure, lipid profile, glucose, and insulin (secondary). At baseline, no significant differences were observed between groups. Per-protocol analysis showed significant differences in BMI and FMI (kg/m2 and z-score) between the intervention and control groups among girls, but not among boys. Intention-to-treat analysis confirmed these findings in girls, showing significant changes in BMI (− 0.68 kg/m2) and BMI z-score (− 0.34) compared with the control group. In both per-protocol and intention-to-treat analyses, no significant between-group differences were observed in changes in cardiovascular risk factors.

Conclusion: A Mediterranean lifestyle intervention may benefit body composition changes in preschool girls at risk of obesity; larger studies are needed to confirm these sex-specific results.

Trial registration: ClinicalTrials.gov: NCT04597281. Date of register: 28–09-2020.https://www.clinicaltrials.gov/study/NCT04597281?id=NCT04597281&rank=1What is Known:• Mediterranean diet-based interventions have shown benefits in reducing BMI and obesity in children and adolescents. While many studies focus primarily on BMI, fewer have reported detailed body composition measures or explored potential sex-specific effects.What is New:• This is the first randomized controlled trial evaluating the effectiveness and efficacy of a Mediterranean lifestyle prevention intervention—including diet and PA—in preschool children at risk of obesity. Including FMI and the FMI z-score enables more specific characterization of adiposity-related changes, which complement BMI-based outcomes.

What is Known:

• Mediterranean diet-based interventions have shown benefits in reducing BMI and obesity in children and adolescents. While many studies focus primarily on BMI, fewer have reported detailed body composition measures or explored potential sex-specific effects.

What is New:

• This is the first randomized controlled trial evaluating the effectiveness and efficacy of a Mediterranean lifestyle prevention intervention—including diet and PA—in preschool children at risk of obesity. Including FMI and the FMI z-score enables more specific characterization of adiposity-related changes, which complement BMI-based outcomes.

The online version contains supplementary material available at 10.1007/s00431-026-06844-3.