Abstract and Introduction

Abstract

Introduction Socioeconomic status may influence childhood obesity prevalence and children’s fitness level. The purpose of this study was to assess the association between family income and children’s physical fitness level and obesity prevalence for 8 racial/ethnic groups.

Methods Data for 1,617,400 fifth-, seventh-, and ninth-grade children who took a physical fitness test from 2010 through 2012 in California were used in this cross-sectional study. Multiple linear and log-binomial regressions were used to test whether low family income (as indicated by eligibility for National School Lunch Program) was associated with physical fitness level or obesity prevalence. Differences were tested by race/ethnicity while adjusting for age and sex. Fitness score was measured on a scale from 0 (least healthy) to 6 (most healthy).

Results Average fitness score was 4.45 (standard deviation, 1.47). Prevalence of obesity was 20.3%, and 56% of children were classified as having lower family income. Lower family income (vs higher) was associated with lower fitness score (coefficient = −0.57; 95% confidence interval [CI], −0.62 to −0.53). Lower-income children had higher prevalence of obesity (relative risk = 1.81; 95% CI, 1.72–1.89) compared with higher-income children. These inverse associations were seen among American Indian, Asian, Pacific Islander, Filipino, Hispanic/Latino, African American, and white children and among children who were identified as being of 2 or more races/ethnicities.

Conclusion Children with lower family incomes tend to have less healthy physical fitness status and have higher risk of obesity than children with higher family incomes. This information can be used to help set policies and provide programs aimed at improving fitness and decreasing obesity risk among low-income children.

Introduction

Childhood obesity and physical inactivity are major public health concerns; 32% of US children are either overweight or obese, and only 37% of students meet the physical activity recommendations of at least 60 minutes on at least 5 days per week.^[1,2] Obese children have higher risk of obesity in adulthood,^[3] which is associated with comorbidities.^[4] Physical inactivity is an independent risk factor for obesity and cardiovascular disease among children.^[5]

Socioeconomic status (SES) may play a role in both childhood obesity prevalence and children’s physical fitness levels. Low SES can be a barrier to physical activity and healthful eating,^[6–8] and children who regularly perform high-intensity activity tend to be more physically fit.^[9] Previous studies have reported that children of low SES have higher risk of obesity than children of high SES.^[6,7] Fewer studies have examined the effect of SES on physical fitness. Although racial/ethnic disparities in obesity have been reported,^[1,10] few studies have examined the relationship between SES and obesity within racial/ethnic groups. Data from the US National Health and Nutrition Examination Survey (NHANES) indicated that SES is associated with lower risk for obesity only among white children.^[11] However, in that study, children with a range of ages (2–19 years) were grouped together; the sample size was only moderately sized after stratifying by race and sex; and only white, African American, and Hispanic populations were included.

We used data from children and adolescents from 8 racial/ethnic groups in California to assess the association between family income and 1) children’s physical fitness level, 2) children’s body mass index (BMI) z-score, and 3) childhood obesity. We hypothesized that children living in lower-income families would have lower physical fitness levels and higher risk for obesity and that the magnitude of the association may differ among racial/ethnic groups. On the basis of previous literature,^[1,10] we hypothesized that the associations would be stronger for boys than girls.