Genetic and environmental contributions to weight, height, and BMI from birth to 19 years of age: an international study of over 12,000 twin pairs.

OBJECTIVE: To examine the genetic and environmental influences on variances in weight, height, and BMI, from birth through 19 years of age, in boys and girls from three continents. DESIGN AND SETTINGS: Cross-sectional twin study. Data obtained from a total of 23 twin birth-cohorts from four countries: Canada, Sweden, Denmark, and Australia. Participants were Monozygotic (MZ) and dizygotic (DZ) (same- and opposite-sex) twin pairs with data available for both height and weight at a given age, from birth through 19 years of age. Approximately 24,036 children were included in the analyses. RESULTS: Heritability for body weight, height, and BMI was low at birth (between 6.4 and 8.7% for boys, and between 4.8 and 7.9% for girls) but increased over time, accounting for close to half or more of the variance in body weight and BMI after 5 months of age in both sexes. Common environmental influences on all body measures were high at birth (between 74.1-85.9% in all measures for boys, and between 74.2 and 87.3% in all measures for girls) and markedly reduced over time. For body height, the effect of the common environment remained significant for a longer period during early childhood (up through 12 years of age). Sex-limitation of genetic and shared environmental effects was observed. CONCLUSION: Genetics appear to play an increasingly important role in explaining the variation in weight, height, and BMI from early childhood to late adolescence, particularly in boys. Common environmental factors exert their strongest and most independent influence specifically in pre-adolescent years and more significantly in girls. These findings emphasize the need to target family and social environmental interventions in early childhood years, especially for females. As gene-environment correlation and interaction is likely, it is also necessary to identify the genetic variants that may predispose individuals to obesity.

Sex differences in the association between sleep duration, diet and body mass index: a birth cohort study.

Sex differences in the effects of sleep duration on dietary intake and eating behaviours were examined prospectively in relation to overweight/obesity at ages 6 and 7. Using data from a representative sample (QLSCD 1998-2010) of children born in the province of Québec (Canada), 1106 children were followed to age 6 and 1015 to 7years. Average nocturnal sleep duration was surveyed annually from 2.5-6years, food-frequency and eating behaviour questionnaires were administered at age 6, and body weight and height were measured at 6 and 7years. Associations were examined longitudinally and mediation examined with adjustments for potential confounders. In boys and girls, shorter sleep duration patterns were associated significantly with less favourable dietary intakes at 6years: boys consumed vegetables and fruits less frequently and meats/alternatives more frequently than boys with longer sleep patterns; and girls consumed vegetables, fruits and milk products less frequently and soft-drinks more frequently than girls with longer sleep patterns. However, boys with shorter sleep patterns were also more likely to eat at irregular hours or to eat too much/fast at 6years. These behaviours, and not dietary intake, mediated an inverse association between sleep duration and overweight/obesity in boys. Sleep duration did not associate with any problem eating behaviours or overweight/obesity in girls. Shorter sleep in early childhood appears to associate with problematic eating behaviours in boys and diet quality in both sexes, regardless of an association with overweight/obesity. This is important for public health and should be considered in relation to other diet-related diseases.

Higher intakes of energy and grain products at 4 years of age are associated with being overweight at 6 years of age.

This study examined dietary factors associated with overweight in a population-based sample of 6-y-old children. Analyses of data from the Québec Longitudinal Study of Child Development (QLSCD) included a representative sample (n = 1014) of children born in 1998 in the province of Québec, Canada. Dietary intake was measured by using a 24-h dietary recall administered at 4 y of age. Weight and height were measured using a standard protocol at 6 y. Using logistic regression, higher daily energy intake at 4 y was significantly related to overweight at 6 y. After adjustment for confounding and overweight at 4 y, the relationship remained significant among girls (P = 0.04) but became marginally significant among boys (P = 0.07). Additionally, boys who consumed ≥5 servings of grain products/d at 4 y were more likely to be overweight at 6 y compared to those who did not [adjusted OR = 3.20 (95% CI): 1.72-5.97]. The association attenuated somewhat after adjustment for overweight at 4 y [OR = 1.82 (95% CI): 0.894-3.71; P = 0.09]. The findings provide support for the revisions made in the Canadian dietary guidelines for young children, which now recommend 4-7 servings of grain products daily for children aged 4-8 y rather than the excessive 5-12 servings of previous recommendations.

Household food insecurity and childhood overweight in Jamaica and Québec: a gender-based analysis.

BACKGROUND: Childhood overweight is not restricted to developed countries: a number of lower- and middle-income countries are struggling with the double burden of underweight and overweight. Another public health problem that concerns both developing and, to a lesser extent, developed countries is food insecurity. This study presents a comparative gender-based analysis of the association between household food insecurity and overweight among 10-to-11-year-old children living in the Canadian province of Québec and in the country of Jamaica. METHODS: Analyses were performed using data from the 2008 round of the Québec Longitudinal Study of Child Development and the Jamaica Youth Risk and Resiliency Behaviour Survey of 2007. Cross-sectional data were obtained from 1190 10-year old children in Québec and 1674 10-11-year-old children in Jamaica. Body mass index was derived using anthropometric measurements and overweight was defined using Cole's age- and sex-specific criteria. Questionnaires were used to collect data on food insecurity. The associations were examined using chi-square tests and multivariate regression models were used to estimate odds ratios (OR) and 95% confidence intervals. RESULTS: The prevalence of overweight was 26% and 11% (p < 0.001) in the Québec and Jamaican samples, respectively. In Québec, the adjusted odds ratio for being overweight was 3.03 (95% CI: 1.8-5.0) among children living in food-insecure households, in comparison to children living in food-secure households. Furthermore, girls who lived in food-insecure households had odds of 4.99 (95% CI: 2.4-10.5) for being overweight in comparison to girls who lived in food-secure households; no such differences were observed among boys. In Jamaica, children who lived in food-insecure households had significantly lower odds (OR 0.65, 95% CI: 0.4-0.9) for being overweight in comparison to children living in food-secure households. No gender differences were observed in the relationship between food-insecurity and overweight/obesity among Jamaican children. CONCLUSIONS: Public health interventions which aim to stem the epidemic of overweight/obesity should consider gender differences and other family factors associated with overweight/obesity in both developed and developing countries.

Breakfast skipping is associated with differences in meal patterns, macronutrient intakes and overweight among pre-school children.

OBJECTIVES: To examine the association between skipping breakfast, daily energy, macronutrients and food intakes, and BMI in pre-school children. DESIGN: A cross-sectional study using information on children's food consumption and measured height and weight. Energy and macronutrient intakes of the children were derived from parent/day-care attendant's responses to 24 h recall interviews and eating behaviour questionnaires. SETTING: Data obtained from a representative sample (n 2,103) of children born in Quebec (Canada) in 1998. SUBJECTS: One thousand five hundred and forty-nine children, with a mean age of 49 (sd 3.12) months. RESULTS: Ten per cent of children ate breakfast on fewer than 7 days per week. This behaviour was associated with a lower diet quality and concentrated energy intakes through higher protein intakes at lunch and the consumption of snacks higher in energy and carbohydrate in the afternoon and evening; yet total daily energy intakes were not significantly different from those of pre-school children who ate breakfast every day. Breakfast skippers' mean BMI increased as intake of energy, carbohydrates or servings of grain products increased; however, this was not the case for breakfast eaters. When Cole's cut-off for overweight/obesity was used, overweight/obesity in breakfast skippers was related to the dinner-time consumption of approximately 3,000 kJ (700 kcal) or more for energy intake, approximately 100 g or more of carbohydrates, or approximately 3 servings or more of grain products. CONCLUSIONS: Eating breakfast every day is associated with having a healthy body weight, likely due to a more even distribution of energy intake across meals throughout the day.

Psychosocial determinants of the early introduction of complementary foods.

Infant feeding guidelines recommend exclusive breast-feeding to the age of 6 months; complementary foods should not be introduced before this age. This study examined parent and infant psychosocial determinants of the early introduction of complementary foods. Analyses were conducted on a representative sample of children born in Québec (Canada) in 1998 (n = 2,223), surveyed through the Québec Longitudinal Study of Child Development. Of the children, 61% received complementary foods prior to the age of 4 months. A multiple logistic regression analysis revealed the early introduction of complementary foods was more likely when mothers were younger, less educated, of lower socioeconomic class, and when they felt they had little influence on their child's development. Higher parental confidence in caring for the infant was also associated with the early introduction of complementary foods (p < or = .05). Future research must carefully consider the psychosocial aspects involved in adhering to infant feeding guidelines.

Determinants of high birth weight by geographic region in Canada.

This study aims to analyze the determinants of high birth weight (> 4000 grams) by various geographic regions of Canada. Analyses were performed using the data from cycles 1 to 4 (1994-2001; N=20,002 children) of the Canadian National Longitudinal Survey of Children and Youth (NLSCY). Children were grouped into five geographic residential area categories: the Atlantic provinces, Quebec, Ontario, the Prairie provinces and British Columbia. Determinants analyzed in the study include sex, gestational age and birth rank of children; maternal age and education; maternal smoking during pregnancy; family type; family socioeconomic status (SES) and maternal health (postpartum depression; hypertension and prescription drug use during pregnancy). In comparison to Quebec, the odds of giving birth to a high-birth-weight child were 25 percent higher in Ontario, 41 percent higher in the Atlantic provinces and 53 percent higher in British Columbia. In Quebec, non-smoking mothers of higher SES had increased odds of delivering a baby weighing more than 4000 grams, while in British Columbia, the odds of having a birth weight greater than 4000 grams doubled for children of non-smoking mothers from the lowest SES quintiles. The relationship between social disparities and macrosomia was found to vary by geographic region.

Problem eating behaviors related to social factors and body weight in preschool children: A longitudinal study.

BACKGROUND: Despite the increasing prevalence of overweight/obesity and its association to eating patterns in adolescents and adults, little is known about the relationship between problematic eating behaviours and body weight in the preschool years within the context of various social factors. This research aims to analyze the relationship between social factors, mothers' perceptions of their child's eating behaviour (picky eating and overeating), and body weight in preschool years, in a population-based cohort of preschoolers from Québec (Canada). METHODS: Analyses were performed on 1498 children from the Longitudinal Study of Child Development in Québec, a representative sample of children born in 1998 in the Canadian province of Québec. Eating behaviours (picky eating and overeating) were derived from questionnaires at 2.5, 3.5, and 4.5 years of age. BMI was calculated from children's measured height and weight at 4.5 years. Children's sex and birth weight, mothers' age, immigrant status, smoking status during pregnancy, and education level, family type, annual household income and income sufficiency, the number of overweight/obese parents, children's day-care attendance, and food insufficiency were part of the analysis. Multivariate logistic regressions were used to determine odds ratios for different body weight profiles (underweight, normal weight, at risk of overweight, overweight), and one-way analysis-of-variances (ANOVA) allowed for group comparisons of means. RESULTS: The proportion of children reported for each eating behaviour category remained quite stable across the years studied. Picky eating and overeating related to body weight among 4.5-year-old children, even when social and parental factors were accounted for in multivariate analysis. Picky eaters were twice as likely to be underweight at 4.5 years as children who were never picky eaters. Adjusted odds ratios revealed overeaters were 6 times more likely to be overweight at 4.5 years than were children who were never overeaters. CONCLUSION: Given the association between eating behaviours and bodyweight among 4.5-year-old children, particularly among those from less educated, lower income families and younger mothers, health professionals should target parents of children at risk of overweight/obesity and underweight with focussed messages and strategies for the management of emerging problematic eating behaviours.