Prevalence of overweight and obesity in a provincial population of Canadian preschool children

Methods

Data were obtained from the records of children who were born in the province of Newfoundland and Labrador in 1997 and who participated in the Preschool Health Check Program, a province-wide screening program conducted by public health nurses before school entry. Although all of the children were born in 1997, because of the variability in the timing of the Preschool Health Check, children's ages ranged from 3.5 years to 5.5 years.

As part of the screening, all children were weighed and their heights measured by the nurse using a standardized procedure. Children were weighed, wearing light clothing, on a calibrated mechanical or electronic step scale. In addition, we obtained the date of the Preschool Health Check and the child's date of birth and sex from the Program's records.

Each child's body mass index (BMI, kg/m²) was calculated from the height and weight measures. We classified each child as being “overweight,” “obese” or “normal” using previously published age- and sex-specific BMIs for children aged 2–18 years, as modified from the accepted cut-off values for adults.9

Results

Data were received for 4469 of the 5428 children born in 1997. Because information was missing for 308 children, the final sample included 4161 children. This sample represents 76.7% of the 1997 birth cohort10 and 79.2% of the children who were subsequently enrolled in kindergarten in 2002.11 Boys and girls were equally represented (50.1% and 49.9% respectively). The response rates did not vary significantly by region, ranging from 73.0% to 84.0%. A description of the sample is presented in Table 1.

The rates of overweight and obesity in this preschool population were high (Fig. 1). There were no significant differences between boys and girls in the prevalence of overweight or obesity (p ≥ 0.05). Similarly, there were no significant differences between age groups in the prevalence of overweight or obesity (p ≥ 0.05). There were no significant sex-by-age interactions in prevalence.

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Fig. 1: Prevalence of overweight (squares) and obesity (triangles) among preschool children in Newfoundland and Labrador, by sex and age group. Error bars represent 95% confidence intervals.

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Figure 1. Continued.

Interpretation

This study represents the first province-wide report on the prevalence of overweight and obesity among preschool children in Canada based on directly measured heights and weights. Our results indicate that more than 1 in 4 preschool children in Newfoundland and Labrador are already overweight or obese. The magnitude of the problem may reflect the fact that the province's rates of overweight and obesity among older children and adults are the highest in the country.

Without comparable data from other provinces, we do not know whether the prevalence observed in our study would be seen in other provinces. However, the prevalence of overweight and obesity among older children and adults is increasing everywhere in Canada, having doubled between 1981 and 1996 in 9 out of 10 provinces.12 In fact, Willms and colleagues12 concluded from their study of Canadian children aged 7–13 years that the risk of being overweight is related more to the secular trend than to demographic or geographic variables. Recent reports of the prevalence among teenagers in Canada indicate that the trend is continuing.13

The prevalence of overweight and obesity in Newfoundland and Labrador is similar to the prevalence among preschoolers in other countries based on measured heights and weights. A 1998 United Kingdom study reported a prevalence of 23.6% among children aged 2.9–4 years.14 In Australia, 18.0% of children 2–6 years old were overweight or obese. These countries also reported increasing prevalence of overweight and obesity among older children and adults.

One aim of our study was to determine the age at which overweight and obesity emerge in preschool children. We found that more than 25% of children as young as 3.5 years, the youngest in our study, were overweight or obese. A report from the United States has indicated that children less than 2 years old are showing a trend toward a higher weight for height.15 Together these results clearly indicate the need to examine adiposity in children less than 3.5 years of age. In places like Newfoundland and Labrador, and other parts of Canada and other developed countries with well-developed health and community nursing systems, monitoring and prevention could be incorporated into existing prenatal and child health programs without a substantial increase in costs. Our data provide a basis upon which future trends in the Canadian preschool population may be monitored and against which prevention measures may be evaluated.

𝛃 See related article page 243