Explaining the Positive Relationship Between Fourth‐Grade Children's Body Mass Index and Energy Intake at School‐Provided Meals (Breakfast and Lunch)

Abstract

BACKGROUND A positive relationship exists between children’s body mass index (BMI) and energy intake at school-provided meals. To help explain this relationship, we investigated 7 outcome variables concerning aspects of school-provided meals—energy content of items selected, number of meal components selected, number of meal components eaten, amounts eaten of standardized school-meal portions, energy intake from flavored milk, energy intake received in trades, and energy content given in trades. METHODS We observed children in grade 4 (N=465) eating school-provided breakfast and lunch on one to 4 days per child. We measured children’s weight and height. For daily values at school meals, a generalized linear model was fit with BMI (dependent variable) and the 7 outcome variables, sex, and age (independent variables). RESULTS BMI was positively related to amounts eaten of standardized school-meal portions (p < .0001) and increased 8.45 kg/m2 per serving, controlling for other variables in the model. BMI was positively related to energy intake from flavored milk (p = .0041) and increased 0.347 kg/m2 for every 100-kcal consumed. BMI was negatively related to energy intake received in trades (p = .0003) and decreased 0.468 kg/m2 for every 100-kcal received. BMI was not significantly related to 4 outcome variables. CONCLUSIONS Knowing that relationships between BMI and actual consumption, not selection, at school-provided meals explained the (previously found) positive relationship between BMI and energy intake at school-provided meals is helpful for school-based obesity interventions.

Secondary analyses of data from 4 studies with fourth-grade children show that sex, race, amounts eaten of standardized portions, and energy content given in trades explain the positive relationship between body mass index and energy intake at school-provided meals

“…First, BMI was positively related to amounts eaten of standardized school-meal portions. This result is intuitive and was also found by Guinn and colleagues [13] with data from a study with a sample of predominantly Black children in a district in Columbia, South Carolina that had implemented offer-versus-serve foodservice (as mentioned in the Introduction). Second, BMI was negatively related to energy content given in food trades.…”

“…Although this result is also intuitive, the relationship between BMI and energy intake received in food trades was not significant after accounting for all other independent variables. Guinn and colleagues [13] found that BMI was negatively related to the percentage of energy intake received in food trades at school meals even after accounting for the other aspects studied in that article.…”

“…Guinn and colleagues [13] found that BMI was positively related to energy intake from flavored milk. Although flavored milk in schools has become a controversial issue due to the added sugar when compared to plain milk, results from this article’s analyses contribute to the body of evidence indicating that consumption of flavored milk, dietary calcium, and/or dairy foods may not be related to obesity [34–38].…”

“…Meal composition was the same whether children paid full price or received meals for free or at a reduced price. Unlike the 2010 publication by Baxter and colleagues [10] and the recent publication by Guinn and colleagues [13], this district had not implemented offer-versus-serve foodservice, so children could not refuse meal components [27]. In other words, for lunch, each child’s meal included an entrée (from two choices), milk, two servings of vegetable or fruit, and bread/grain.…”

“…Results from the Third School Nutrition Dietary Assessment Study showed that offering elementary school children french fries or dessert more than once per week at school lunch was associated with higher BMI [12]. To explain the positive relationship between BMI and energy intake at school-provided meals found in the 2010 publication (mentioned in the previous paragraph), secondary analyses by Guinn and colleagues [13] showed that BMI was (a) positively related to amounts eaten of standardized portions, (b) positively related to energy intake from flavored milk, and (c) negatively related to energy intake received in food trades. However, BMI was not significantly related to the energy content of items selected, the number of meal components selected, the number of meal components eaten, or the percentage of energy content given in food trades [13].…”