Time spent in school was shown to have a beneficial impact on students' weight, especially for students who were overweight or obese. However, these results are alarming because weight gain during elementary school occurs primarily during the relatively short span of summer break.

The results indicate that an obesity prevention program where health professionals assist teachers by integrating healthy messages into existing curriculum was effective in reducing zBMI compared to the SH condition.

Objective: To examine seasonal variation in weight gain across elementary school (kindergarten-5th grade) among children who are healthy weight, overweight, or obese and from different racial and ethnic groups. Methods: The sample included 7,599 ethnically diverse students ages 5-7 years at baseline (Caucasian: 21.1%, Black: 36.2%, Hispanic: 26.0%, Asian 16.7%). Heights and weights were measured by school nurses at the beginning and end of each school year from kindergarten through the beginning of 5th grade. Results: Beginning the summer after 1st grade, all children demonstrated a pattern of standardized BMI (zBMI) increases during the summer (0.04 to 0.09) and zBMI decreases across the school years (20.06 to 0.00; P < 0.0001). Hispanic children and children who were overweight and obese exhibited this pattern in kindergarten while children of other ethnicities and with a healthy weight did not (P < 0.0001). Conclusions: Beginning the summer after 1st grade, a consistent pattern of relative weight gain during the summer months (D in BMI percentile 5 1.04) and weight loss during the school year (D in BMI percentile 5 20.34) emerged. This pattern appeared earlier for children who were overweight, obese, or Hispanic. These findings suggest a need to better understand the causes of the problematic increases in weight during the summer.

The NSLP has been widely criticized; however, conducting a comparison in this manner demonstrates advantages to children obtaining school lunches. Although it was beyond the scope of this study to examine diet quality (e.g., actual intake and nutrient/caloric density), these results provide compelling evidence that lunches brought from home should be an area of emphasis for research and intervention.

BackgroundLittle is known about patterns in the transition from healthy weight to overweight or obesity during the elementary school years. This study examined whether there were distinct body mass index (BMI) trajectory groups among elementary school children, and predictors of trajectory group membership.MethodsThis is a secondary analysis of 1651 elementary school children with complete biannual longitudinal data from kindergarten to the beginning of 5th grade. Heights and weights were measured by trained school nurses using standard procedures at the beginning and end of each school year for 11 consecutive assessments. Group-based trajectory clustering and multinomial logit modeling were conducted.ResultsWhen using BMIz score, six trajectory groups were identified revealing substantial consistency in BMIz score across time. When using a categorical variable separating overweight/obese children (BMI ≥ 85%ile) from the rest, five developmental trajectories (persistently non-overweight/obese weight: 51.1 %; early-onset overweight/obese: 9.2 %; late-onset overweight/obese: 9.7 %; becoming healthy weight: 8.2 %; and chronically overweight/obese: 21.8 %) were identified. When using a categorical variable separating obese children (BMI ≥ 95%ile) from the rest, three trajectories (persistently non-obese: 74.1 %, becoming obese: 12.8 %; and chronically obese: 13.2 %) were identified. For both cutoffs (≥ BMI percentile 85 % or 95 %), girls were more likely than boys to be classified in the persistently non-overweight and/or obese group (odds ratios (OR) ranged from 0.53 to 0.67); and Hispanic children and non-Hispanic Black children were more likely to be chronically overweight and/or obese than non-Hispanic White children (OR ranged from 1.57 to 2.44). Hispanic children were also more likely to become obese (OR: 1.84) than non-Hispanic White children when ≥ BMI percentile 95 % was used.ConclusionsBoys, Hispanic and non-Hispanic Black children were at higher risk of being overweight or obese throughout their elementary school years, supporting the need for obesity treatment. Post kindergarten and post second grade summer months were times when some children transitioned into overweight/obesity. It will be important to identify which behavioral factors (e.g., diet, physical activity, sedentary behaviors, and/or sleep) predisposed children to becoming overweight/obese, and whether these factors differ by time (Kindergarten versus second grade). If behavioral predisposing factors could be identified early, targeted obesity prevention should be offered.