The prevalence of childhood overweight and obesity continues to increase among youth [1
]. In efforts to reduce childhood obesity, many health-promoting interventions targeting modifiable risk factors, such as diet and physical activity, have been employed but have shown varying degrees of success [2
]. While it is important to modify such risk factors, there may be environmental risk factors, such as seasonal periods, that are also important. Currently, the context of how seasonal periods affect weight status among children is not well understood. Some point to the in-school environment as an especially obesogenic time. With in-school cafeterias and vending machines, children have access to many competitive foods that are not required to meet USDA nutrition standards that federally subsidized meals are required. Children are also given little time to engage in physical activities as P.E. classes and recess are being cut [4
]. Others point to the out of school environment as an at risk time for weight gain. At home, children engage in a large amount of screen time [6
], frequent convenient stores and fast food restaurants that serve energy-dense/nutrient poor foods [7
], and are monitored less by parents as the need increases for both parents or guardians to have full-time employment [4
To determine if the in or out of school time contributed more to childhood overweight, Von Hipple and colleagues compared gains in body mass index (BMI) among kindergarten and 1st grade children during the school and summer vacation months [4
]. During the school year, kindergarten and 1st grade children’s BMI increased by 0.02 units and 0.033 units per month respectively, while during the summer vacation months the average increase more than doubled, with an average increase of 0.076 units per month [4
]. Another study with middle and upper elementary American Indian children found somewhat similar results. Investigators reported that over the summer vacation, 3rd and 5th grade girls BMI and weight significantly increased, and 4th grade boys BMI significantly increased. Overweight and obese children also experienced a significantly higher gain in their BMI compared with their normal weight peers [8
]. Together, these studies suggest that children are at greater risk for gaining extra weight during unstructured, out of school months.
Another unstructured-out-of-school time, albeit shorter in length compared with summer recess, is the holiday break, which typically spans from early December to early January. Adults commonly believe they gain 5 pounds during these months, however studies have shown actual weight gain is typically much less [8
]. This time may be especially important to monitor children’s weight due to changes in eating and physical activity patterns that often accompany the holidays. It is generally agreed that during this time more holiday foods are eaten, which tend to be calorically dense. Bad weather conditions can also encourage children and families to stay in-doors and engage in more sedentary activities. In the study previously mentioned, Smith and colleagues evaluates changes in BMI during this time, and found that a small but significant increase in BMI was observed among fifth grade children [8
]. It is important to note however, that this study used a homogenous group of American Indian children, making it difficult to generalize to children belonging to other racial groups.
While previous studies indicated a trend towards higher weight gains during the unstructured-out-of-school month, no studies reported children’s BMI-percentile (BMI-%) as an indicator of weight status. Evaluating ‘excess’ or ‘extra’ weight gain can be difficult among children since they are naturally growing, and absolute BMI does not account for normal growth as well as BMI-% [9
]. The purpose of this study was to evaluate gains in height, weight, and BMI during the holidays, and compare these results with childrens BMI-% to control for normal growth. Since previous research found differences among genders and normal and overweight children, differences between these groups were also explored.