The main aim of the present study was to examine the association between the Dietary Inflammatory Index (DII®) and academic performance in children.

School-based cross-sectional study. The DII was calculated based on dietary information obtained from a single 24h dietary recall. Academic performance was assessed by school records provided by the administrative services (i.e. Maths and Language).

Porto area (Portugal).

A total of 524 children (277 girls) aged 11·56 (sd 0·86) years.

The DII was associated with academic indicators (standardized β values ranging from −0·121 to −0·087; all P<0·05). Significant differences were found between quartiles of the DII (P<0·05); children in the fourth quartile had significantly lower scores in all academic indicators compared with children in the first quartile (score differences ranging from −0·377 to −0·292) after adjustment for potential confounders.

The inflammatory potential of diet may negatively influence academic performance. Children should avoid the consumption of a pro-inflammatory diet and adhere to a more anti-inflammatory diet to achieve academic benefits.

To examine the association between obesity and food group intakes, physical activity and socio-economic status in adolescents.

A cross-sectional study was carried out in 2008. Cole's cut-off points were used to categorize BMI. Abdominal obesity was defined by a waist circumference at or above the 90th percentile, as well as a waist-to-height ratio at or above 0·500. Diet was evaluated using an FFQ, and the food group consumption was categorized using sex-specific tertiles of each food group amount. Physical activity was assessed via a self-report questionnaire. Socio-economic status was assessed referring to parental education and employment status. Data were analysed separately for girls and boys and the associations among food consumption, physical activity, socio-economic status and BMI, waist circumference and waist-to-height ratio were evaluated using logistic regression analysis, adjusting the results for potential confounders.

Public schools in the Azorean Archipelago, Portugal.

Adolescents (n 1209) aged 15–18 years.

After adjustment, in boys, higher intake of ready-to-eat cereals was a negative predictor while vegetables were a positive predictor of overweight/obesity and abdominal obesity. Active boys had lower odds of abdominal obesity compared with inactive boys. Boys whose mother showed a low education level had higher odds of abdominal obesity compared with boys whose mother presented a high education level. Concerning girls, higher intake of sweets and pastries was a negative predictor of overweight/obesity and abdominal obesity. Girls in tertile 2 of milk intake had lower odds of abdominal obesity than those in tertile 1. Girls whose father had no relationship with employment displayed higher odds of abdominal obesity compared with girls whose father had high employment status.

We have found that different measures of obesity have distinct associations with food group intakes, physical activity and socio-economic status.

There are no percentile curves for BMI, waist circumference (WC) or waist-to-height ratio (WHtR) available for Portuguese children and adolescents. The purpose of the present study was to develop age- and sex-specific BMI, WC and WHtR percentile curves for a representative sample of adolescents living in the Portuguese islands of Azores, one of the poorest regions of Europe, and to compare them with those from other countries.

Cross-sectional school-based study. Weight, height and WC were objectively measured according to standard procedures. Smoothed percentile curves were estimated using Cole's LMS method.

Azores, Portugal.

Proportionate stratified random sample of 1500 adolescents, aged 15–18 years.

Results showed some sex differences in the shape of the BMI curves: in girls, the upper percentile values tend to decrease by the age of 16 and 17 years; whereas in boys, the upper percentiles tend to be flat between 15 and 16 years and then increase until the age of 18 years. In both sexes, the upper percentile values of both WC and WHtR decreased slightly by the age of 16 years and then increased steeply. In both sexes, the Azorean values for the 50th and 90th WC percentiles were higher than those reported for adolescents from the majority of other countries.

The reference curves presented herein provide baseline data for the long-term surveillance of Azorean adolescents, as well as for national and international comparisons.