Seasonal variability in body mass index change among children enrolled in the Pediatric Obesity Weight Evaluation Registry: A step in the right direction.

BACKGROUND: Research has shown children disproportionately gain excess weight over the summer months (vs. school months), with stronger effects for children with obesity. However, the question has not been investigated among children receiving care in paediatric weight management (PWM) programs. OBJECTIVE: To test for seasonal variability in weight change among youth with obesity in PWM care enrolled in the Pediatric Obesity Weight Evaluation Registry (POWER). METHOD: Longitudinal evaluation of a prospective cohort from 2014 to 2019 among youth in 31 PWM programs. Change in percentage of the 95th percentile for BMI (%BMIp95) was compared by quarter. RESULTS: Participants (N = 6816) were primarily ages 6-11 (48%), female (54%), 40% non-Hispanic White, 26% Hispanic and 17% Black, and 73% had severe obesity. Children were enrolled on average 424.9 ± 401.5 days. Participants reduced their %BMIp95 every season, but compared with Quarter 3 (July-September), reductions were significantly greater in Q1 (Jan-March, b = -0.27, 95%CI -0.46, -0.09), Q2 (April-June, b = -0.21, CI -0.40, -0.03), and Q4 (October-December, b = -0.44, CI -0.63, -0.26). CONCLUSION AND RELEVANCE: Across 31 clinics nationwide, children reduced their %BMIp95 every season, but reductions were significantly smaller during the summer quarter. While PWM successfully mitigated excess weight gain during every period, summer remains a high-priority time.

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.