Early life growth trajectories and future risk for overweight.

OBJECTIVE: Standard approaches have found that rapid growth during the first 2 years of life is a risk factor for overweight in later childhood. Our objective was to test whether growth velocity, independent of concurrent size, was associated with overweight using a nonlinear random-effects model that allows for enhanced specifications and estimations. METHODS: Longitudinal data from a birth cohort in Mexico (n=586) were used to estimate growth trajectories over 0-24 months for body mass index (BMI), length and weight using the SuperImposition by Translation and Rotation (SITAR) models. The SITAR models use a nonlinear random-effects model to estimate an average growth curve for BMI, length and weight and each participant's deviation from this curve on three dimensions-size, velocity and timing of peak velocity. We used logistic regression to estimate the association between overweight status at 7-9 years and size, velocity and timing of BMI, length and weight trajectories during 0-24 months. We tested whether any association between velocity and overweight varied by relative size during 0-24 months or birth weight. RESULTS: SITAR models explained the majority of the variance in BMI (73%), height (86%) and weight (85%) between 0-24 months. When analyzed individually, relative BMI/length/weight (size) and BMI/length/weight velocity during 0-24 months were each associated with increased odds of overweight in late childhood. Associations for timing of peak velocity varied by anthropometric measure. However, in the mutually adjusted models, only relative BMI/length/weight (size) remained statistically significant. We found no evidence that any association between velocity and overweight varied by size during 0-24 months or birth weight. CONCLUSIONS: After mutual adjustment, size during 0-24 months of life (as opposed to birth size), but not velocity or timing of peak velocity, was most consistently associated with overweight in later childhood.

Emerging disparities in overweight by educational attainment in Chinese adults (1989-2006).

OBJECTIVE: To test whether a disparity in overweight by socioeconomic status (SES; represented by educational attainment) has emerged among men or women during a recent 17-year period in China. METHODS: Data from the China Health and Nutrition Survey (CHNS), a panel study including 7314 women and 6492 men, are used to longitudinally track the body mass index (BMI) and odds of overweight by educational attainment among Chinese adults (baseline age 18-50) from 1989 to 2006 to determine whether individuals of low (secondary school) educational attainment experienced a disproportionately faster increase in BMI or odds of overweight (BMI≥25) over time. The unadjusted mean BMI and prevalence of overweight by education are presented. Sex-stratified, random-effects models are used to estimate the associations, and interactions by birth cohort are included. FINDINGS: Overweight prevalence doubled for women and tripled for men. In 1989, among women, the odds of overweight were not different for those of high versus those of low educational attainment; however, by 2006, the odds of overweight were significantly lower for those with the highest education in both the younger (odds ratio (OR) 0.22 (CI 0.11, 0.42)) and the older (OR 0.27 (CI 0.10, 0.72)) birth cohorts. The reverse trend is seen for men, who also begin with no difference in odds of overweight by SES, but by 2006, the OR for the highest versus the lowest education group was 3.4 (CI 1.82, 6.18). CONCLUSIONS: Over 17 years, low SES has become associated with higher BMI and odds of overweight among Chinese women, whereas high SES remains a risk factor for overweight among Chinese men.

Is the burden of overweight shifting to the poor across the globe? Time trends among women in 39 low- and middle-income countries (1991-2008).

BACKGROUND: Overweight prevalence has increased globally; however, current time trends of overweight prevalence by social class in lower income countries have not been fully explored. METHODS: We used repeated cross-sectional, nationally representative data from the Demographic and Health Surveys on women aged 18-49 years with young children (n=421,689) in 39 lower-income countries. We present overweight (body mass index ≥ 25 kg m⁻²) prevalence at each survey wave, prevalence difference and prevalence growth rate for each country over time, separately by wealth quintile and educational attainment. We present the correlation between nation wealth and differential overweight prevalence growth by wealth and education. RESULTS: In the majority of countries, the highest wealth and education groups still have the highest prevalence of overweight and obesity. However, in a substantial number of countries (14% when wealth is used as the indicator of socioeconomic status and 28% for education) the estimated increases in overweight prevalence over time have been greater in the lowest- compared with the highest-wealth and -education groups. Gross domestic product per capita was associated with a higher overweight prevalence growth rate for the lowest-wealth group compared with the highest (Pearson's correlation coefficient: 0.45). CONCLUSIONS: Higher (vs lower) wealth and education groups had higher overweight prevalence across most developing countries. However, some countries show a faster growth rate in overweight in the lowest- (vs highest-) wealth and -education groups, which is indicative of an increasing burden of overweight among lower wealth and education groups in the lower-income countries.