The Foundation for Active Healthy Kids

Over one-third of Canadian children aged 2 to 11 were overweight in 1998/99, and of these, about half could be considered obese, according to a snapshot of childhood obesity from the National Longitudinal Survey of Children and Youth.

In 1994/95, 34% of children aged 2 to 11 were overweight, with an estimated 16% classified as obese. By 1998/99, 37% of children aged 2 to 11 were overweight, including 18% who were classified as obese. These observations were made on the basis of the international definitions for child overweight and obesity.

In recent years, childhood obesity and low levels of activity have emerged as important issues facing Canadian children. Obesity in adults is linked to greater health risks, including the increased incidence of coronary disease and type-2 diabetes, although it has also been found that increased activity can temper these negative effects.

NLSCY estimates on obesity among children were slightly higher than estimates for adults determined by the 2000/01 Canadian Community Health Survey. These data, released in The Daily on May 8, 2002, showed that about 32% of adults were overweight, including 15% who were classified obese. The youngest adult age group (20 to 24) was the least overweight.

Note to readers

The National Longitudinal Survey of Children and Youth (NLSCY), developed jointly by Human Resources Development Canada and Statistics Canada, is a comprehensive survey that follows the development of children in Canada and paints a picture of their lives. This longitudinal survey, conducted every two years, monitors children's development and measures the incidence of various factors that influence this development, both positively and negatively.

The first cycle of the NLSCY, conducted in late 1994 and early 1995, interviewed parents of children up to the age of 11. They gave information, not only about their children, schools and neighbourhoods, but also about themselves and their families. In cycles two and three, self-reported data were collected from children over the age of 12 for weight and height, and other variables were self-reported for age 10 and older.

The third cycle of the NLSCY, carried out in 1998 and 1999, surveyed the same children, who were between 4 and 15 years of age, as well as new children aged zero to five. Again, self-reported data were collected for children between the ages of 10 and 15. This release will focus on information from all three cycles for children aged 2 to 11, collected from 1994/95 to 1998/99.

The NLSCY collects parent-reported or self-reported data for height and weight and does not include directly measured values. This may result in some under-estimation of the levels of obesity in Canadian children.

Body mass index (BMI) was calculated using self-reported height and weight data for children over age 11 in each cycle, and from parent-reported data for children aged 11 or younger. The BMI is calculated by dividing weight in kilograms by height in meters squared. International cut-offs for children were used to classify children as obese, overweight or neither overweight nor obese. The child cut-offs are age- and gender-specific for children aged 2 to 20. For example, a boy aged 12 who was 1.1 metres tall, would be considered obese if he weighed 32.5 kg.

Activity levels were determined from questions on participation in organized activities, such as sports or dance classes, and unorganized activities, such as bicycling. Those who were not participating in activity at least once a week were classified as inactive. Those who participated in activities approximately 4 or more times a week were classified as active. For this survey information on intensity or duration of the activity was not collected.

More boys than girls were overweight

The overall estimate of children in Canada aged 2 to 11 who were overweight has increased since 1994. In all three cycles of the NLSCY, more boys than girls were overweight. In 1998/99, an estimated 35% of girls and 38% of boys were overweight, including 17% of girls and 19% of boys who were classified obese.

Age differences in levels of obesity were also seen, as fewer of the older children were obese. One in four children between the ages of two and five were obese in all three cycles, compared with 1 in 10 children aged 8 to 11.

Low income one factor in childhood obesity

Higher proportions of children living in low-income families were overweight and obese.

In 1998/99, one-quarter of children aged 2 to 11 living in families with incomes below the low-income cut-off (LICO) were obese; only 16% of children in families above the LICO were in this weight category. The proportion of overweight and obese children decreased as the family income increased.

More obese children inactive

In 1998/99, the percentage of children aged 4 to 11 years of age who were classified as normal weight and overweight (non-obese) were similar in terms of activity levels. Obese children's overall activity levels were considerably different from the other two groups of children.

Fewer obese children (38%) were active compared with non-obese children (47%). Additionally, more obese children (38%) were inactive compared with non-obese children (30%).

Majority of children overweight at some point

The NLSCY collects data from the same respondents every two years. As a result it is possible to examine changes in the body mass index over time. The following section focusses on a four-year period for the same youth, aged 6 to 15 in 1998/99, who were between the ages of 2 and 11 in 1994/95.

From 1994/95 to 1998/99, about 44% of children were never overweight and about 10% were consistently overweight in all four years. The remainder, about 56%, were overweight in at least one year of this time period.

For the group of children followed longitudinally, the proportion who were overweight decreased from 1994 to 1999. In 1994/95, 32% of the children were overweight. Four years later, 28% of these same children were overweight.

In addition, the levels of obesity also decreased from 14% in 1994/95 to 10% in 1998/99. This decrease may have been a result of the children growing older. In all three cycles of data, the oldest age group was always the least overweight.