Changing Influences on Childhood Obesity: A Study of 2 Generations
Changing Influences on Childhood Obesity: A Study of 2 Generations
Explanations for the trend of increasing childhood obesity have yet to be identified. The authors examined members of the 1958 British birth cohort (age 7 years, n = 8,552) and offspring (ages 4–9 years, n = 1,889) born to mothers under age 30 years to establish whether risk factors for childhood obesity have changed over time (1965–1991). The authors applied multilevel linear and logistic models that account for within-family correlations in order to examine associations between risk factors and childhood body mass index (BMI; weight (kg)/height (m)) (age- and sex-specific standard deviation scores and overweight/obesity) in the 2 populations. The authors found that the prevalence of overweight/obesity had increased by more than 50% between generations. Parental BMI and full-time maternal employment were both positively associated with offspring BMI in childhood (e.g., an increase of 0.4–0.5 units for maternal employment); these associations had strengthened between generations. There was evidence of a widening social gap in childhood obesity: Indicators of lower socioeconomic position showed either no association or a protective effect in cohort members but were associated with increased BMI in offspring. Prevalences of parental obesity and maternal employment had increased. Socioeconomic factors had improved across generations. Parental obesity, maternal employment, and socioeconomic factors may play an increasing role in the childhood obesity epidemic.
The prevalence of child obesity continues to rise in Britain and elsewhere. An increase in mean triceps skinfold thickness of approximately 10% among 7-year-olds in England and Scotland was documented between 1972 and 1994, and this increase was greater after 1984. The prevalence of overweight/obesity among children aged 2–10 years increased from 22.7% to 27.7% in England between 1995 and 2004. Although some recent evidence suggests that the increase may be slowing down, the high prevalence of child obesity is likely to result in further increases in adult obesity and its associated health consequences.
It is likely that the rapid increase in childhood obesity is mainly driven by environmental changes affecting behavior and lifestyle rather than changes in genetic predisposition, because the increase has occurred over a short period of time, within a relatively constant gene pool. However, few studies have examined changes in potential causal factors that underlie the trend. The prevalence or strength of some influences on the development of childhood obesity may have changed over time. These changes could have contributed to recent trends.
We used data from 2 generations of the 1958 British birth cohort to examine risk factors for childhood obesity in different time periods to gain insight into the possible causes leading to the secular increase. Our study built on previous research from the 1958 cohort, wherein parental obesity and birth weight were found to be associated with the development of obesity, while maternal smoking during pregnancy and social class in childhood were found to be associated with adult obesity. Other studies have suggested a protective effect of breastfeeding against obesity. As yet, the question of whether risk factors for obesity in a cohort generation are evident in the next generation has not been explored. We aimed to establish whether influences on childhood obesity have changed in strength or prevalence between 1958 cohort members and their offspring and whether these changes have contributed to the trend in childhood obesity.
Abstract and Introduction
Abstract
Explanations for the trend of increasing childhood obesity have yet to be identified. The authors examined members of the 1958 British birth cohort (age 7 years, n = 8,552) and offspring (ages 4–9 years, n = 1,889) born to mothers under age 30 years to establish whether risk factors for childhood obesity have changed over time (1965–1991). The authors applied multilevel linear and logistic models that account for within-family correlations in order to examine associations between risk factors and childhood body mass index (BMI; weight (kg)/height (m)) (age- and sex-specific standard deviation scores and overweight/obesity) in the 2 populations. The authors found that the prevalence of overweight/obesity had increased by more than 50% between generations. Parental BMI and full-time maternal employment were both positively associated with offspring BMI in childhood (e.g., an increase of 0.4–0.5 units for maternal employment); these associations had strengthened between generations. There was evidence of a widening social gap in childhood obesity: Indicators of lower socioeconomic position showed either no association or a protective effect in cohort members but were associated with increased BMI in offspring. Prevalences of parental obesity and maternal employment had increased. Socioeconomic factors had improved across generations. Parental obesity, maternal employment, and socioeconomic factors may play an increasing role in the childhood obesity epidemic.
Introduction
The prevalence of child obesity continues to rise in Britain and elsewhere. An increase in mean triceps skinfold thickness of approximately 10% among 7-year-olds in England and Scotland was documented between 1972 and 1994, and this increase was greater after 1984. The prevalence of overweight/obesity among children aged 2–10 years increased from 22.7% to 27.7% in England between 1995 and 2004. Although some recent evidence suggests that the increase may be slowing down, the high prevalence of child obesity is likely to result in further increases in adult obesity and its associated health consequences.
It is likely that the rapid increase in childhood obesity is mainly driven by environmental changes affecting behavior and lifestyle rather than changes in genetic predisposition, because the increase has occurred over a short period of time, within a relatively constant gene pool. However, few studies have examined changes in potential causal factors that underlie the trend. The prevalence or strength of some influences on the development of childhood obesity may have changed over time. These changes could have contributed to recent trends.
We used data from 2 generations of the 1958 British birth cohort to examine risk factors for childhood obesity in different time periods to gain insight into the possible causes leading to the secular increase. Our study built on previous research from the 1958 cohort, wherein parental obesity and birth weight were found to be associated with the development of obesity, while maternal smoking during pregnancy and social class in childhood were found to be associated with adult obesity. Other studies have suggested a protective effect of breastfeeding against obesity. As yet, the question of whether risk factors for obesity in a cohort generation are evident in the next generation has not been explored. We aimed to establish whether influences on childhood obesity have changed in strength or prevalence between 1958 cohort members and their offspring and whether these changes have contributed to the trend in childhood obesity.