Seasonal Variability in Weight Gain Among American Indian, Black, White, and Hispanic Children: A 3.5-Year Study

Introduction Several studies have reported that children gain more weight during the summer season. Despite high obesity rates, little research has included American Indian/Alaskan Native children, and few studies have been longitudinal. This observational study examines seasonal weight variability over 3.5 years among ethnically diverse children, including 2,184 American Indian/Alaskan Native children. Methods Children's height and weight were measured before and after the summer from 2012–2015 and analyzed in 2019–2020, including children with ≥2 consecutive measurements (N=7,890, mean age=8.4 [SD=2.8] years). Mixed-effects models tested whether the percentage of the 95th BMI percentile and BMI differed by season (summer versus the rest of the year) and ethnicity. Results American Indian/Alaskan Native (23.7%), Hispanic (19.8%), and Black (17.8%) children had significantly higher baseline obesity rates than White children (7.1%). The percentage of the 95th BMI percentile significantly increased during the summer compared with the percentage during the rest of the year, with the strongest effects for children who were obese (b=2.69, 95% CI=1.35, 4.03, p<0.001) or overweight (b=1.47, 95% CI=0.56, 2.35, p<0.01). In BMI units, summer BMI increase was 0.50 kg/m2 higher (obese model) and 0.27 kg/m2 higher (overweight) than that of the rest of the year. Seasonal effects were significantly less pronounced for American Indian/Alaskan Native children than for White children. Conclusions Children gained significantly more weight during the summer season, with the strongest effects for children who were obese. American Indian/Alaskan Native children had less seasonal variability than White children, but higher overall obesity rates. These data underscore summer as a critical time for obesity prevention among children who are overweight/obese but suggest that seasonal patterns may vary for American Indian/Alaskan Native children.