Can the Mediterranean diet protect against childhood overweight and obesity?

New research shows that children who adhere to the Mediterranean diet, especially consuming nuts and vegetables, may experience lower weight gain, but the overall effects are modest after accounting for initial BMI.

In a recent study published in the journal Pediatric Research, researchers examined how following the Mediterranean diet affects changes in standardized body mass index (zBMI) and children's risk of gaining excessive weight. While adherence to the Mediterranean diet was associated with protection against high zBMI increases, these effects were modest and lost statistical significance after adjusting for baseline zBMI.

Their findings indicate that consuming specific Mediterranean diet foods, such as yogurt or cheese, nuts, and vegetables, can protect children against large zBMI increases, although the overall effect size was small.

Background

Childhood obesity rates have significantly increased worldwide, becoming a major public health issue. In Spain, childhood obesity and overweight have remained above 30% for the last 20 years, with recent data suggesting that nearly 41% of children between six and nine years old are overweight and 17% are obese.

The Mediterranean diet emphasizes a high consumption of plant-based foods, such as fruits, vegetables, legumes, nuts, and whole grains, combined with moderate consumption of fish and dairy, which helps to maintain a balanced diet.

Childhood obesity can continue into adolescence and adulthood. Estimates indicate that 55% of children with obesity may remain obese during adolescence and that 80% of obese adolescents will remain obese into adulthood.

Behavioral, environmental, and genetic factors contribute to obesity; researchers have identified low self-esteem, poor sleep, unhealthy diets, and physical inactivity as risk factors that can be modified to address it. For children, lack of physical activity and unhealthy or obesogenic food are the primary drivers of obesity.

The Mediterranean diet, which is rich in fibers, antioxidants, healthy fats, and plant-based proteins, is a balanced diet that may have benefits for weight management in children and has been shown in some studies to lower body mass index (BMI). However, more evidence is needed to fully understand its impact on childhood obesity.

About the study

The study included 1,389 children between the ages of eight and ten from four municipalities in Spain between 2012 and 2014, with a follow-up after 15 months. The children participated voluntarily and with their parents’ permission.

At the start of the study, their waist circumference, height, and weight were measured, and changes in BMI were used to calculate zBMI. A BMI of greater than one standard deviation was categorized as overweight while a BMI of greater than two standard deviations was considered obese.

The children’s adherence to the Mediterranean diet was assessed using a validated questionnaire that trained researchers administered in schools, with higher scores reflecting greater adherence.

Researchers also used questionnaires to measure physical activity over the past week, time spent watching television, using mobile devices, and playing video games. Socioeconomic status was ascertained based on maternal education.

The statistical analysis involved the use of multiple linear and logistic models to examine the relationship between adherence to the Mediterranean diet and changes in zBMI, accounting for lifestyle factors such as zBMI at the start of the study, screen time, physical activity, school environment, and maternal education.

Findings

At the beginning of the study, 9.4% of the children showed low adherence to the Mediterranean Diet, while 49.5% had medium adherence and 41.2% had high adherence.

During the follow-up, adherence to the diet decreased, as did zBMI. However, physical activity, screen time, and BMI showed increases. During the study, 66 new cases of excessive weight were reported, including 64 overweight cases and 2 obesity cases, but the sample size limited the statistical power of this finding.

Researchers found that certain foods from the Mediterranean diet eaten in specific quantities were linked to a lower likelihood of high zBMI increases, including consuming nuts two or three times each week and cheese or yogurt and cooked or fresh vegetables daily.

The diet is associated with longevity and reduced rates of chronic diseases, including heart disease and cancer, making it one of the healthiest eating patterns globally.

Children who showed high or medium adherence to the diet at the beginning of the study were less likely to experience high increases in zBMI, but these results were not statistically significant after adjustments.

The linear regression showed that as the adherence score to the Mediterranean diet at the beginning of the study increased by one point, zBMI decreased. However, this association weakened and became statistically insignificant after accounting for zBMI at baseline.

There were no significant non-linear relationships between diet adherence and changes in zBMI. However, children with adherence scores between 4 and 10 showed slight decreases in zBMI. No significant relationships were observed between adherence to the diet and the incidence of excessive weight.

Conclusions

Previous studies, including those involving North American and European children, have found associations between adherence to the Mediterranean diet and lower BMI, but research involving Spanish adolescents showed inconclusive results. Though certain foods were linked to a lower probability of high zBMI increases, the overall effect was modest, and similar studies in the past have shown inconsistent results.

While the study’s strengths include its large sample size, prospective design, and dose-response analysis, the researchers noted some limitations. The reliance on self-reported dietary data introduces potential biases due to memory or social desirability errors.

The questionnaire also included general descriptions of foods and did not contain some important components of Mediterranean diets. The study also did not account for energy intake and socioeconomic factors other than maternal education.

More high-quality, long-term studies are needed to provide stronger evidence on the Mediterranean diet's role in reducing childhood overweight and obesity.