Mediterranean Diet May Counteract Genetic Risk for Teen Obesity

Aisha I Abdullah PhD avatar

by Aisha I Abdullah PhD |

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The Mediterranean diet reduces obesity-related metrics in adolescents, but it is not as effective in males who have a high genetic risk for obesity, a study has found.

In female adolescents, the diet significantly lowered body mass index (BMI), waist circumference, and metabolic syndrome, even in participants with a relatively high obesity risk. 

The study, “Interaction Effect of the Mediterranean Diet and an Obesity Genetic Risk Score on Adiposity and Metabolic Syndrome in Adolescents: The HELENA Study,” was published in the journal Nutrients.

Metabolic syndrome is a group of conditions closely associated with obesity, including high blood pressure and insulin resistance, that increase the risk for complications such as type 2 diabetes and heart disease.

In European children, high adherence to Mediterranean diet — which is rich in vegetables, fruits, nuts, beans, and whole grains with moderate consumption of dairy, poultry, and eggs, and limited red meat — has been associated with lower childhood and adolescent obesity and improvements in metabolic syndrome-related factors.

A genetic predisposition for obesity can be determined using an obesity genomic risk score (GRS), which combines the effects of obesity-related genetic variations to predict obesity risk. Specifically, GRS uses data from an individual’s single nucleotide polymorphisms (SNPs), which are genetic variations in a single nucleotide, the building block of DNA. 

Researchers in Spain led an international team that sought to evaluate how an obesity GRS, using 21 SNPs associated with weight and obesity, and adherence to the Mediterranean diet affect obesity and metabolic syndrome in European adolescents. The analysis included data from the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study of 4,356 adolescents, ages 11 to 19 years, from 10 European cities between 2006–2007. The median obesity GRS was 23.

“To our knowledge, no studies have examined the interaction effect between [Mediterranean diet] adherence and an obesity-related [genetic risk score] on adiposity and [metabolic syndrome] in European adolescents,” the investigators wrote.

All participants had genetic, health, and dietary information available. Of the 605 HELENA participants included in the study, the median age was 14.7 years, and 312 (51.6%) were female. Compared with males, female participants had a higher average waist circumference and insulin resistance, a weak response to insulin that may result in high blood sugar. Male participants had higher mean and systolic blood pressure and more severe metabolic syndrome.

Results showed that adherence to the Mediterranean diet had a protective effect on BMI, waist circumference, and metabolic syndrome score in males and females. The diet also had a protective effect on insulin resistance and systolic blood pressure in females, and on mean and diastolic blood pressure in male adolescents. The obesity genetic risk and Mediterranean diet interacted to significantly influence blood pressure in males and insulin resistance in female participants. 

Most of the study participants (82.3%) had an obesity score concentrated in the center of the risk distribution, representing 20–26 obesity-related genetic variations. For this group, high adherence to Mediterranean diet had a protective effect on BMI, waist circumference, and metabolic syndrome, an effect that was stronger in female adolescents. However, the diet’s impact was modulated by obesity GRS such that a higher genetic predisposition for obesity reduced the protective effect of the Mediterranean diet on these factors. 

In males with an obesity-related genetic risk score of 22 or lower (46.8% of total), Mediterranean diet adherence lowered BMI. Significantly, this diet decreased the BMI in 98.1% of female participants (risk score of 27 or lower), suggesting that, in female adolescents, the diet can overcome the effect of obesity genetic risk. 

Diet adherence reduced waist circumference and metabolic syndrome severity in 95.2% of females (risk score of 26 or lower). In males, the diet decreased waist circumference in 19.8% (risk score of 20 or lower) and metabolic severity in 4.8% — risk scores of 18 or lower.

High adherence to Mediterranean diet reduced insulin resistance in 89.4% of female adolescents (risk score of 25 or lower), as well as diastolic blood pressure in 31.4% of males with a risk score of 21 or lower and mean blood pressure in 46.8% of males — risk score of 22 or lower.

“As [metabolic syndrome] and excess of adiposity may occur at any stage from childhood to adulthood, early detection and diagnosis is fundamental to elaborate on health prevention programs among youth to effectively reduce the risk of cardiovascular diseases and [type 2 diabetes],” the researchers wrote. “These observations strengthen the idea of applying genomic information to promote targeted dietary advice.”

Among the limitations of the study, according to the investigators, are the fact that they could only use risk gene spots from the HELENA project, thereby not taking into account rarer variants that may also be important for BMI changes.

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