Abstract
This paper examines body mass index (BMI) trajectories among children from different race/ethnic and maternal nativity backgrounds in the United States and England from early- to middle-childhood. This study is the first to examine race/ethnic and maternal nativity differences in BMI trajectories in both countries. We use two longitudinal birth cohort studies—The Fragile Families and Child Wellbeing Study (n = 3,285) for the United States and the Millennium Cohort Study (n = 6,700) for England to estimate trajectories in child BMI by race/ethnicity and maternal nativity status using multilevel growth models. In the United States our sample includes white, black, and Hispanic children; in England the sample includes white, black, and Asian children. We find significant race/ethnic differences in the initial BMI and BMI trajectories of children in both countries, with all non-white groups having significantly steeper BMI growth trajectories than whites. Nativity differences in BMI trajectories vary by race/ethnic group and are only statistically significantly higher for children of foreign-born blacks in England. Disparities in BMI trajectories are pervasive in the United States and England, despite lower overall BMI among English children. Future studies should consider both race/ethnicity and maternal nativity status subgroups when examining disparities in BMI in the United States and England. Differences in BMI are apparent in early childhood, which suggests that interventions targeting pre-school age children may be most effective at stemming childhood disparities in BMI.
Similar content being viewed by others
Introduction
Childhood obesity has increased dramatically in the United States during the past two decades [1], especially among black and Hispanic children and children with immigrant backgrounds [2–6]. A similar increase in obesity rates has occurred in England, almost doubling between 1995 and 2007, [1, 7] although overall rates of obesity are still lower than they are in the United States [8]. In the United States, several studies that examine body mass index (BMI) trajectories document a pattern where school-age children of immigrants gain weight faster than their counterparts with native-born mothers [3, 4, 6]. However, another study using cross-sectional obesity rates at both 9 months of age and 4 years of age did not find these differences [5]. In England, evidence also suggests that Asian children and black children with immigrant mothers are at risk for overweight in middle childhood compared to white children of native-born mothers [9]. In this study we use two nationally representative birth cohort studies to describe and compare trajectories in children’s BMI during early and middle childhood with a special focus on disparities by race, ethnicity and maternal nativity.
Our analysis extends prior research in several ways. First, we estimate BMI trajectories beginning at age three. Whereas prior trajectories research on the children of immigrants typically begins when children enter school, growing evidence suggests that BMI gaps emerge much earlier for some subgroups [10]. Research has also shown that certain patterns of BMI growth in early childhood (e.g. starting out below average and gaining weight rapidly) are more predictive of later life obesity and related health problems than other growth patterns [11, 12]. Second, we examine immigrant/native disparities in obesity along with racial and ethnic disparities. This approach allows us to compare children with immigrant backgrounds not only to children of native-born whites, which is the most common comparison group in past research, but also to children of native-born parents from the same race/ethnic group. Finally, we extend our analysis to include England, in addition to the United States.
Including England has several advantages. First, no study of this kind has been done in England with nationally representative data. Second, including England allows us to examine a broader range of racial, ethnic and maternal nativity groups than has been examined in previous research. Third, despite universal access to health care, the health differentials between ethnic groups (Asians and black African/Caribbeans) and whites in England are of a similar magnitude as the differentials found in the United States for a variety of health outcomes [13, 14]. Finally, while immigrant groups in England are very different from the Hispanic immigrant majority in the United States, immigrants in both countries tend to be low skilled and of low socio-economic status [15]. A comparison of children’s BMI trajectories in these two countries may provide substantial insight into whether children from various racial and ethnic minority backgrounds experience a higher or lower risk of obesity trajectories, whether this risk varies by nativity status, and whether overall patterns vary by country.
Methods
Data
This study relies on two national birth cohort studies that follow children from birth to middle childhood: the Fragile Families and Child Wellbeing Study (FFS) for the United States and the Millennium Cohort Study (MCS) for England. Both studies are based on probability samples and both contain very rich longitudinal information on children and their families. In addition, these studies are particularly well-suited for comparison due to the sampling time frames and the consistency of age at follow-up. The FFS and MCS are publicly available and deidentified data sources. The FFS follows 4,898 children born in large US cities between 1998 and 2000 and is representative of urban births [16]. The FFS oversamples non-marital births and includes a large number of race and ethnic minorities. Mothers and fathers were interviewed in the hospital soon after the birth, and follow-up interviews were conducted when the children were age 1, 3, 5, and 9 years. The FFS sample of immigrant and native-born mothers is similar to the national population as reported in vital statistics, despite being representative of urban births only (available upon request). Weight and height were measured at the 3, 5 and 9 year waves.
The MCS is a nationally representative sample of 18,818 children born in the United Kingdom in 2000–2002 [17]. The first interview was conducted when the child was 9 months and the follow-up interviews were at ages 3, 5, and 7 years. Within England, the survey oversamples disadvantaged areas and areas with a high proportion of ethnic minority residents. For this paper, we exclude Scotland, Wales, and Northern Ireland from the sample, as these countries combined include <150 non-white respondents.
Measures
Body Mass Index
Body mass index is calculated from weight and height measurements for children at ages 3, 5, and 9 in the United States and ages 3, 5, and 7 in England. Raw BMI has been shown to be preferable for measuring adiposity change compared to other BMI measures such as Z-scores and percentiles [18]. It is also frequently used in other studies examining BMI trajectories among children with immigrant backgrounds [3, 4, 6]. For the descriptive analysis, BMI is categorized according to age in months and gender percentiles according to the Center for Disease Control and Prevention (CDC) guidelines. We use the CDC 85th percentile to designate children that are overweight.
Nativity Status and Race/Ethnic Subgroups
In both the MCS and the FFS data, all children are born within England or the United States. We use mothers’ country of birth to determine whether the mother is native- or foreign-born. In the text, we refer simply to nativity for parsimony. We combine mothers’ nativity status with ethnicity to create four separate nativity/race/ethnic categories in the United States and six separate categories in England. In the United States the groups are white native-born, black native-born, Hispanic native-born, and Hispanic foreign-born. The sample size was too small to separately examine foreign-born whites and blacks. In England separate groups of native- and foreign-born coincide with each of the following race and ethnic groups: white, Asian (Pakistani, Bangladeshi, and Indian), and black (Caribbean and African).
Control Variables
Our analysis controls for several variables that are expected to be associated with child’s BMI growth trajectories and race, ethnicity, and nativity. These variables include mothers’ education, age at birth, parity, and whether child was low birthweight (<2,500 g). To measure education we use a dichotomous indicator to distinguish between mothers with ‘high’ and ‘low’ education. In the United States ‘low education’ equals having a high school diploma or less and ‘high education’ equals having some college or more. In England, the measure picks up a similar level of skill by categorizing mothers who have completed O-levels or less as ‘low education’, and those mothers who have completed A-levels or the vocational equivalent or higher as ‘high education’ [19]. Mothers’ marital status at delivery is included in all of the models to adjust for the oversampling of unmarried mothers in the FFS data. We estimated additional models that included a number of other typical child obesity model covariates, such as income, breastfeeding, and maternal employment (available upon request), but these sensitivity analyses did not impact the findings.
Statistical Methods
We use the Stata 13 SE statistical package to estimate growth curve models for children’s BMI trajectories by race/ethnicity/nativity subgroups in both countries [20]. This type of modeling has been used extensively in the literature on nativity and BMI in the United States. The growth model simultaneously estimates a BMI intercept and slope for each child across age (level 1). It also estimates of how these intercepts and slopes differ by each child’s race, ethnicity and nativity (level 2). We present tables with two separate models for each country—one without controlling for covariates and one controlling for covariates. We also include figures that further illustrate the differences in initial BMI at age 3 and trajectories in BMI for the different groups within each country.
Results
Table 1 presents sample characteristics by race/ethnicity and maternal nativity status for the two countries. The sample varies for each of the four subgroups in the United States and for each of the six subgroups in England. As compared with their white counterparts, native-born black mothers in the US are younger, less likely to be married, and less educated than native-born whites; their children are also twice as likely to be low birthweight. Native-born Hispanics are similar to blacks in terms of mothers’ age, education and marital status. However, children of native-born Hispanic women have rates of low birthweight that are similar to the rates of white women. Finally, foreign-born Hispanics are closer to whites with respect to mothers’ age and marital status, but further from whites with respect to education. Most notably, the children of Hispanic immigrant mothers have very low levels of low birthweight, which are lower than the children of native-born white mothers.
We also observed differences across race/ethnic/nativity groups in England. Asian mothers tend to be younger than whites, whereas black mothers tend to be older. Foreign-born mothers are slightly older than their native-born counterparts. Marriage is higher among Asian mothers and lower among black mothers, as compared with whites, with foreign-born mothers having a slightly higher prevalence of marriage than native-born mothers. Rates of low birthweight are substantially higher among Asian and Black mothers (regardless of nativity status) and substantially lower among foreign-born whites, as compared with native-born whites. Finally, whereas levels of education are similar for native-born mothers in England, they differ dramatically among foreign-born mothers, with foreign-born whites twice as likely to have high levels of education as foreign-born Asians and Blacks.
Overweight Rates and Mean BMI
Table 2 presents overweight rates (percentages) and BMI levels (means) for children at age 3 in the United States and England. Not surprisingly, in the US, children born to Hispanic mothers (both native-born and foreign-born) have overweight rates that are 1.5 times higher than children born to white and black mothers. Children born to Hispanic mothers also have the highest mean BMI.
In England, Asian children show lower levels of overweight than children born to white mothers, with minimal difference between native- and foreign-born mothers. In contrast, Black children have higher rates of overweight than children of other ethnicities, particularly children of black immigrant mothers who have the highest rates of overweight. A similar pattern can be seen in mean BMI by subgroup.
Growth Trajectories
Results from the growth model analysis are presented in Table 3. The first model adjusts for marital status at birth only. The second model adjusts for the other control variables. Although the coefficients change slightly when the control variables are included in the model, the general pattern for intercepts (baseline) and trajectories (growth) stays largely the same.
The intercept coefficients represent the race/ethnic/nativity differences in baseline BMI at age 3. The reference group is native-born whites in both countries, and all continuous variables are centered at the mean. In the US (model 2), BMI at baseline is significantly higher for both native- and foreign-born Hispanics as compared to native-born whites, but this difference is not present between the two Hispanic groups. Blacks actually have slightly lower BMI at baseline than whites, though this difference is not statistically significant. Growth trajectories in the US follow a similar pattern with native- and foreign-born Hispanics experiencing steeper trajectories than the trajectories of native-born whites. We find no difference in the change in BMI between the Hispanic children of foreign-born mothers and US-born mothers. All Hispanic children start out heavier at age 3 and have a more rapid and statistically significant increase in BMI than white children. Black children at age 3 have a BMI that is very similar to that of white children; but, like Hispanics, their BMI increases at a significantly faster rate than whites.
In England (models 3 and 4), children of both native- and foreign-born Asians have significantly lower BMI at age 3 than children of native-born whites, with slightly lower levels among children of foreign-born mothers. Black children of native- and foreign-born mothers are similar to whites. In England, we see divergent patterns in growth by race/ethnic and nativity subgroup. The BMI slopes of Asian children, with native- and foreign-born mothers, are steeper than the slopes of native-born whites. Black children of native-born mothers have an even steeper slope than children born to Asian mothers. Strikingly, the rate of weight gain is highest for children of foreign-born blacks. While there appears to be little effect of mother’s foreign-born status on the BMI trajectories among Hispanic children in the United States, in England we find an immigrant disadvantage for blacks and a slight immigrant advantage for Asian children. Overall, Asian children of both native- and foreign-born mothers start out thinner than white children of native-born mothers at age 3 but gain weight at a faster rate that is statistically significant. The BMI level of Asian children will likely surpass that of whites if the growth rate remains the same. Black children of native-born mothers start out heavier than black children of foreign-born mothers at age 3, but children with foreign-born mothers gain much faster. The rate of growth between native- and foreign-born whites is the same.
Additional analyses with interactions using generational status (1.5 vs. 1st generation) rather than foreign-born status, length of residence, income, and stratified by ethnic group all find the same patterns described above (available upon request). Additionally, sensitivity analysis that examines gender differences in trajectories within each race/ethnic/nativity group show that girls gain slower than boys for children of foreign-born Hispanic mothers in the United States, and that girls gain at a faster rate than boys for children of foreign born black mothers in England. No significant gender differences are present for any other group (available upon request). Finally, we also run the growth models separately for the married and non-married samples, and the patterns in BMI trajectories by race/ethnicity/nativity also hold.
It is worth noting that the different ages at which BMI is measured in the two countries—United States (3, 5, and 9) and England (3, 5, and 7)—may have an impact on our results. Children typically show higher BMI during the toddler years, reduced BMI around preschool/kindergarten years, and then an adiposity rebound around age 6, on average [21]. The overall steeper slopes in the United States may reflect the fact that children age 9 have spent more time in this post-adiposity rebound period than children age 7 in England.
Discussion
In this study we expand our understanding of race/ethnic/nativity differences in body weight trajectories in the United States and England by: (1) examining children’s trajectories beginning in toddlerhood, (2) including a comprehensive analysis of racial and ethnic differences in tandem with nativity differences, and (3) extending the analysis to England using nationally representative data and examining both race/ethnic and nativity subgroups. Overall our findings show significant differences in initial BMI and BMI slope by race/ethnicity in both countries. They also show that the impact of nativity status differs across race/ethnic groups in the two countries. In the United States, Hispanic and black children are on track to be significantly heavier than white children, which is consistent with broad race/ethnic trends, [2] but their respective patterns of gain are very different. Whereas the Hispanic-white gap is apparent at age 3 and continues to widen over time, the Black-white gap does not emerge until after age three (see Fig. 1). In England, Asian children start out much thinner than white children; but they gain weight at an increased rate. If current rates continue, Asian children will catch up to and surpass whites by young adulthood, which is consistent with the literature on ethnic differences in adult obesity in England [22–25]. Black children in England show a similar pattern to blacks in the US: a small and insignificant gap at age 3, followed by a steep gain in BMI after age 3 (see Fig. 2).
We find some evidence of compensatory growth patterns in both countries—children are small at birth and in early toddlerhood and yet gain weight rapidly during childhood—which may predispose children to health risks as adults [12]. Our findings suggest that while a child may appear to be at a healthy weight at age 3, they may be at risk for obesity and obesity-related diseases at later ages. Thus, for black children in the United States and for black and Asian children in England, consideration of the entire child trajectory in BMI is important.
We also find important differences by maternal nativity status, but only in England. These findings differ from US studies using the Early Childhood Longitudinal Study-Kindergarten Cohort that find that children of immigrant mothers have steeper BMI trajectories than children of native-born mothers, [3, 4, 6] but is consistent with the US Early Childhood Longitudinal Study-Birth Cohort study examining cross-sectional differences in child BMI at ages 9 months and 4 years [5]. Whereas in the United States, children of both native-born and immigrant Hispanic mothers show a similar pattern of high BMI at age 3 and steep slopes, in England we observe two distinct patterns. Asian children of foreign-born mothers start out thinner and gain weight at a slower rate than Asian children of native-born mothers. The children of black mothers have the opposite pattern, with children of foreign-born mothers gaining weight at twice the rate of children of native-born mothers. It appears that the influence of nativity on child weight varies substantially by race/ethnicity, and it is important for future research into overweight and obesity among children with immigrant backgrounds to consider this heterogeneity. Future studies that have larger samples of children of immigrants are warranted, particularly studies that allow for disentangling the influence of region of origin and acculturation.
Racial and ethnic minority groups in both countries have early childhood trajectories that suggest that disparities in obesity by race/ethnicity are formed between 3 and 7 years of age (or even earlier for Hispanic children). It appears that in the United States the children of Hispanic mothers (both native- and foreign-born) are most at risk for obesity during the early life course, while in England, black children—particularly children with foreign-born mothers—are most at risk. Due to the unique time period in body weight development examined in our study, we might also be able to surmise that these racial and ethnic minority groups in both countries are experiencing the adiposity rebound at an earlier age than white children. Adiposity rebound at young ages (average age is 6) is associated with significantly higher likelihood of obesity as an adult [21, 26]. Thus, our findings provide further evidence for obesity prevention interventions in early childhood, with a primary focus on reducing disparities by ethnic/nativity groups in both countries [27].
As the period surrounding the adiposity rebound appears to be at the age that BMI is increasing for blacks in the United States and England, and Asians in England, the early preschool and early school-age years are an important window for policy interventions. Our findings suggest childcare and school-based interventions might be particularly relevant for these groups [28, 29]. Hispanic children in the United States are already at much higher risk than white children at age 3, thus very early interventions might be necessary as well. Evidence is emerging to suggest that maternal health and prenatal influences could also be important intervention points, particularly among groups showing disparities in high BMI and overweight at early ages [30].
As with most studies, this study has some limitations. The first limitation is the inability to further parse out the race/ethnic categories into more fine-grained groups in both the United States and England. Additionally, as with any longitudinal data, both the US and English data reflect sample attrition with each subsequent survey wave. Finally, we can only examine differences in trajectories within each country due to the differences in the final age of BMI measurement (age 9 in United States and age 7 England).
In summary, the similarities in the obesity burden shared by race/ethnic minority groups in both countries implies that England’s lower childhood obesity rate compared to the United States and equal access to health services are not enough to prevent substantial disparities in BMI trajectories. It appears that more targeted interventions are required in both countries. Finally, the results here show that both healthcare-based and education-based interventions need to be accessible to children with immigrant parents—who are less likely to participate in a variety of services—as these children are also at significant risk of obesity [31].
Abbreviations
- BMI:
-
Body mass index
- US:
-
United States
References
OECD (2010). Obesity: Past and projected future trends. In Obesity and the economics of prevention: Fit not fat. OECD Publishing. doi:10.1787/9789264084865-7-en.
Ogden, C.L., Lamb. M. M., Carroll, M. D., Flegal, K. M. (2010). Obesity and socioeconomic status in children and adolescents; United States 2005–2008; NCHS Data Brief No. 51.
Van Hook, J., & Balistreri, K. S. (2007). Immigrant generation, socioeconomic status, and economic development of countries of origin: A longitudinal study of body mass index among children. Social Science and Medicine, 65(5), 976–989.
Balistreri, K. S., & Van Hook, J. (2009). Socioeconomic status and body mass index among Hispanic children of immigrants and children of natives. American Journal of Public Health, 99(12), 2238–2246.
Li, N., Strobino, D., Ahmed, S., Minkovitz, C. S. (2010). Is there a healthy foreign born effect for childhood obesity in the United States? Maternal and Child Health Journal.
Van Hook, J., & Baker, E. (2010). Big boys and little girls: Gender, acculturation, and weight among young children of immigrants. Journal of Health and Social Behavior, 51(2), 200–214.
Stamatakis, E., Zaninotto, P., Falaschetti, E., Mindell, J., & Head, J. (2010). Time trends in childhood and adolescent obesity in England from 1995 to 2007 and projections of prevalence to 2015. Journal of Epidemiology and Community Health, 64(2), 167–174.
Martinson, M. L., Teitler, J. O., Reichman, N. E. (2011) Health across the life span in the United States and England. American journal of Epidemiology. doi:10.1093/aje/kwq325.
Martinson, M. L., McLanahan, S., & Brooks-Gunn, J. (2012). Race/ethnic and nativity disparities in child overweight in the United States and England. The Annals of the American Academy of Political and Social Science, 643, 219–238.
Hamilton, E., Teitler, J. O., Reichman, N. (2011). Mexican American birthweight and child overweight: Unraveling a possible early lifecourse health transition. Journal of Health and Social Behavior, 52(3), 333–348.
Parsons, T. J., Power, C., & Manor, O. (2001). Fetal and early life growth and body mass index from birth to early adulthood in 1958 British cohort: Longitudinal study. BMJ British Medical Journal, 323(7325), 1331–1335.
Barker, D., Eriksson, J., Forsén, T., & Osmond, C. (2002). Fetal origins of adult disease: Strength of effects and biological basis. International Journal of Epidemiology, 31(6), 1235–1239.
Nazroo, J., Jackson, J., Karlsen, S., & Torres, M. (2007). The black diaspora and health inequalities in the US and England: Does where you go and how you get there make a difference? Sociology of Health and Illness, 29(6), 811–830.
Teitler, J. O., Reichman, N. E., Nepomnyaschy, L., & Martinson, M. (2007). A cross-national comparison of racial and ethnic disparities in low birth weight in the United States and England. Pediatrics, 120(5), e1182–e1189.
Tienda, M. (2005). Growing up in the United Kingdom and the United States: Comparative contexts for youth development. In M. Rutter & M. Tienda (Eds.), Ethnicity and causal mechanisms (pp. 21–49). NY: Cambridge University Press.
Reichman, N. E., Teitler, J. O., Garfinkel, I., & McLanahan, S. S. (2001). Fragile families: Sample and design. Children and Youth Services Review, 23(4/5), 303–326.
Plewis, I., Calderwood, L., Hawkes, D., Hughes, G., & Joshi, H. (2004). Millenium Cohort Study: Technical report on sampling (3rd ed.). London, United Kingdom: Institute of Education.
Cole, T. J., Faith, M. S., Pietrobelli, A., & Heo, M. (2005). What is the best measure of adiposity change in growing children: BMI, BMI%, BMI z-score or BMI centile? European Journal of Clinical Nutrition, 59(3), 419–425.
Jackson, M. S., Kiernan, K., & McLanahan, S. (2012). Immigrant-native differences in child health: Does maternal education narrow or widen the gap? Child Development, 83(5), 1501–1509.
Singer, J. D., & Willett, J. B. (2003). Applied longitudinal data analysis. New York: Oxford University Press.
Rolland-Cachera, M., Deheeger, M., Bellisle, F., Sempe, M., Guilloud-Bataille, M., & Patois, E. (1984). Adiposity rebound in children: A simple indicator for predicting obesity. The American Journal of Clinical Nutrition, 39(1), 129–135.
Jebb, S. A., Rennie, K. L., & Cole, T. J. (2004). Prevalence of overweight and obesity among young people in Great Britain. Public Health Nutrition, 7(03), 461.
Wardle, J., Brodersen, N. H., Cole, T. J., Jarvis, M. J., & Boniface, D. R. (2006). Development of adiposity in adolescence: Five year longitudinal study of an ethnically and socioeconomically diverse sample of young people in Britain. BMJ, 332(7550), 1130–1135.
Balakrishnan, R., Webster, P., & Sinclair, D. (2008). Trends in overweight and obesity among 5–7-year-old white and South Asian children born between 1991 and 1999. Journal of Public Health, 30(2), 139–144.
Harding, S., Maynard, M. J., Cruickshank, K., & Teyhan, A. (2008). Overweight, obesity and high blood pressure in an ethnically diverse sample of adolescents in Britain: The Medical Research Council DASH study. International Journal of Obesity, 32(1), 82–90.
Rolland-Cachera, M., Deheeger, M., Maillot, M., & Bellisle, F. (2006). Early adiposity rebound: Causes and consequences for obesity in children and adults. International Journal of Obesity, 30, S11–S17.
Kumanyika, S., & Grier, S. (2006). Targeting interventions for ethnic minority and low-income populations. Future of Children, 16(1), 187–207.
Story, M., Kaphingst, K. M., & French, S. (2006). The role of schools in obesity prevention. Future of Children, 16(1), 109–142.
Story, M., Kaphingst, K. M., & French, S. (2006). The role of child care settings in obesity prevention. Future of Children, 16(1), 143–168.
Barker, D. J. P. (2013). The developmental origins of chronic disease. In N. Landale, S. McHale, & A. Booth (Eds.), Family and child health (pp. 3–11). NY: Springer.
Borjas, G. J. (2011). Poverty and program participation among immigrant children. Future of Children, 21(1), 247–266.
Acknowledgments
This research was funded in part by Grant T32HD001763 from the National Institutes of Health.
Conflict of interest
None.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Martinson, M.L., McLanahan, S. & Brooks-Gunn, J. Variation in Child Body Mass Index Patterns by Race/Ethnicity and Maternal Nativity Status in the United States and England. Matern Child Health J 19, 373–380 (2015). https://doi.org/10.1007/s10995-014-1519-7
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10995-014-1519-7