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Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References

Objective: To investigate ethnic differences in obesity and physical activity among Aboriginal and non-Aboriginal Canadians.

Methods and Procedures: The sample included 24,279 Canadians (1,176 Aboriginals, 23,103 non-Aboriginals) aged 2–64 years from the 2004 Canadian Community Health Survey (CCHS). Adult participants were classified as underweight/normal weight, overweight (BMI 25–29.9 kg/m2) or obese (BMI ≥ 30 kg/m2). Children and youth 2–17 years of age were classified as normal weight, overweight or obese based on the International Obesity Task Force criteria. Leisure-time physical activity levels over the previous 3 months were obtained by questionnaire in those aged 12–64 years.

Results: The prevalence of obesity in adults was 22.9% (men: 22.9%; women: 22.9%), and the prevalence was higher among Aboriginals (37.8%) compared to non-Aboriginals (22.6%). The prevalence of obesity in children and youth was 8.2% (boys: 9.2%; girls: 7.2%), and the prevalence was higher among Aboriginals (15.8%) compared to non-Aboriginals (8.0%). In both youth and adults, the odds for obesity were higher among Aboriginals (youth: OR = 2.3 (95% CI: 1.4–3.8); adults: OR = 2.4 (95% CI: 1.6–3.6)) after adjustment for a number of covariates. There were no ethnic differences in the prevalence of physical inactivity; however, physical inactivity was a predictor of obesity in both the Aboriginal and non-Aboriginal samples.

Discussion: The prevalence of obesity is higher among Canadian Aboriginals compared to the rest of the population. Further research is required to better delineate the determinants of obesity and the associated health consequences in this population.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References

Several studies have documented a trend toward increasing levels of overweight and obesity in Canada (1,2,3,4), a trend that has paralleled the increases seen in many developed and developing nations (5). The most recent data indicate that the prevalence of obesity has increased from 13.8 in 1978/79 to 23.1% in 2004 among Canadian adults (4). Although limited, there is also evidence that the prevalence of obesity varies quite substantially across ethnic groups in Canada. Results from the Canadian Community Health Survey (CCHS) (2000/01–2003) indicate that the lowest prevalence of self-reported obesity is amongst East–Southeast Asians, while Aboriginal Canadians (living off the reserve) have the highest prevalence (6). These results are also supported by several smaller regional studies of Aboriginal Canadians that have documented a high prevalence of overweight and obesity (7,8,9,10,11,12,13). In addition to a high prevalence of obesity per se, evidence is accumulating regarding the extent of obesity-related morbidities among the Aboriginal peoples of Canada. For example, a high prevalence of type 2 diabetes, metabolic syndrome, and cardiovascular risk factors have been reported among several Aboriginal groups (12,14,15,16,17). Thus, studies of obesity and its determinants among Aboriginal Canadians have an important role to play in informing public health initiatives for this group.

According to recent estimates, the Aboriginal population of Canada includes approximately 1 million people, representing 3.4% of the population, and the annual growth rate of the aboriginal population over the next few years (1.8%)is expected to be more than double the rate projected for the entire population (0.7%) (18). On the other hand, life expectancy among the Aboriginal Canadians remains substantially lower than the total population (18). Thus, an emphasis should be placed on understanding the major health concerns among Aboriginal groups.

Unfortunately, most of the information available on obesity and its determinants among Aboriginal Canadians has been obtained from small regional studies conducted over the last couple of decades. A single report has presented contemporary representative data on obesity among specific ethnic groups, including Aboriginal Canadians (6); however, the prevalence of obesity was based on self-reported data. Given the limitations associated with self-reported health data (19,20), the purpose of this study was to examine the prevalence of measured obesity among Aboriginal Canadians and compare them to general population estimates. Information on several demographic and lifestyle variables, including physical activity, was also examined in relation to the prevalence of obesity.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References

Sample

The data used in this study are from the 2004 CCHS Cycle 2.2: Nutrition. The 2004 CCHS 2.2: Nutrition was designed to gather information at the provincial level about the nutritional status of the Canadian population (21). The target population of the CCHS includes all household residents in all provinces across Canada with the principal exclusion of populations on Indian Reserves, Canadian Forces Bases, residents of institutions and residents in some remote areas. Dwellings were selected using a multistage stratified cluster design employing four different sampling frames (Labour Force Survey; CCHS 2.1 dwellings; PEI and Manitoba Healthcare registries). Details of the sampling methodology are available elsewhere (21). It should be noted that the sampling strategy involved over-sampling Aboriginal Canadians 19–50 years of age (living off-reserve), to obtain nationally representative data in this ethnic group. The overall response rate for the CCHS 2.2: Nutrition was 76.5%. Measured height and weight were obtained for 65.5% of the 6- to 18-year-olds, and 57.5% of the adults who responded to the CCHS 2.2: Nutrition (4,22).

The sample for the present analysis was restricted to participants between 2 and 64 years of age that provided data for age, sex, and either measured BMI or physical activity, which yielded a final sample size of 24,279. It should be noted that sample sizes vary from analysis to analysis due to missing data (BMI: n = 16,974; physical activity: n = 19,824). For each analysis, sample sizes were maximized by deleting missing observations in a listwise manner.

The CCHS 2.2: Nutrition is part of Canada's official statistics program. All protocols and procedures underwent approval through standard internal Statistics Canada committees and processes, and the consent of the participants was implicit by their participation in the survey.

Measures

Age was calculated from birth and observation dates and was truncated to the nearest completed year (i.e., 6 years = 6.0–6.9 years). Height was measured with no shoes, feet together, after a deep inspiration using an anthropometric tape and recorded to the nearest 0.5 cm. Weight was measured in light clothing with no shoes, using a digital electronic scale (LifeSource MD, Milpitas, CA) and was recorded to the nearest 0.01 kg. The BMI was calculated as weight (kg)/height (m2). Adults 18–64 years of age were divided into BMI categories of underweight/normal weight (BMI < 25 kg/m2), overweight (BMI 25–29.9 kg/m2) and obesity (BMI ≥ 30 kg/m2) (23). Children and youth 2–17 years of age were divided into BMI categories of normal weight, overweight, and obese based on the international age- and sex-specific cut-offs published by Cole et al. (24). Self-reported heights and weights were also collected among adults, which allowed for a comparison of the self-reported prevalence of overweight and obesity between this and other surveys.

Physical activity levels were estimated using an interviewer-administered questionnaire for participants aged 12 years and older. Physical activity levels were based upon total energy expenditure during leisure time. EE was calculated from the reported frequency and duration of all of a respondent's leisure time physical activities in the 3 months before the interview and the metabolic energy demand (metabolic equivalent (MET) value) of each activity, which was independently established (25):

  • image

where Ni = number of occasions of activity i in the past 3 months, Di = average duration in hours of activity i, and METi = a constant value for metabolic energy cost of activity i. For the purpose of this analysis, the sample was divided into physically inactive (<1.5 KKD), moderately active (1.5–3.0 KKD), and active (≥3.0 KKD) categories. In addition to the physical activity energy expenditure, participants 12–17 years of age were also asked about the amount of time spent in sedentary activities including time spent watching television or videos, playing video games, and working on a computer, which was categorized into two groups: (i) <20 h, (ii) ≥20 h.

Ethnicity was self-ascribed and was based on questionnaire responses to a question the interviewer read to the respondent that allowed for 13 different ethnic categories to be chosen (including “other”), and also allowed for multiple answers. The responses allowed for the identification of participants who were Aboriginal only (n = 858), mixed-Aboriginal (n = 318) or non-Aboriginal (n = 23,103). Among those who indicated an Aboriginal ancestry, 678 identified themselves as North-American Indian (First Nation), 451 as Métis, and 40 as Inuit, while 7 participants did not respond to this question. Unfortunately, the sample sizes for the specific Aboriginal subgroups (North-American Indian/Métis/Inuit or Aboriginal-only/mixed-Aboriginal) were too small to analyze separately, so the data were retained in the two broad ethnic categories of Aboriginal and non-Aboriginal.

Data on several demographic and lifestyle covariates were collected by questionnaire. Income adequacy groups were created which combined information on annual household income and the size of the household. Income adequacy was categorized into four standard Statistics Canada groups: (i) lowest, (ii) lower-middle, (iii) upper-middle, and (iv) highest (21). Education level was grouped into four categories based on attainment: (i) less than secondary school graduation, (ii) secondary school graduation, (iii) some post-secondary education, and (iv) post-secondary degree/diploma. Cigarette smoking was also classified into four categories: (i) daily smoker, (ii) occasional smoker, (iii) former smoker, (iv) never a smoker.

Statistical analyses

Descriptive statistics and the prevalence figures for physical inactivity, overweight, and obesity were calculated. The prevalence figures for physical inactivity, overweight, and obesity were weighted so they would be representative of the Canadian household population. Given that data on measured height and weight were not available for all participants, an adjustment was made to account for non-response bias. Briefly, several variables, including province, sex, age, household income, education, physical activity, fruit and vegetable consumption, and the presence of chronic conditions, were used to create propensity classes, which were, in turn, used to create special sampling weights for the respondents with measured heights and weights (21). Logistic regression was used to predict obesity and physical inactivity among adults based upon ethnicity in a series of three models. The first model included age and sex as covariates (Model 1), the second model included age, sex, smoking status, household income, and education (Model 2), and the third model included either physical activity levels or body weight category in addition to all covariates from Model 2 (Model 3). Among youth of 12–17 years of age, a single model that included ethnicity, sex, age (as a continuous variable) and physical activity levels was used. To account for the complex sampling strategy used in the CCHS 2.2: Nutrition, coefficients of variation and 95% confidence intervals were estimated using the bootstrap technique (26,27,28). According to Statistics Canada's policy, prevalence estimates with a co-efficient of variation between 16.6 and 33.3% are identified and should be “interpreted with caution,” while those with a co-efficient of variation >33.3% are withheld (21). All data management and statistical analyses were conducted using SAS version 9.1 (Cary, NC).

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References

The descriptive characteristics, of the analysis sample from the Canadian Community Health Survey 2.2: Nutrition, are provided in Table 1, divided by sex, age group, and ethnicity.

Table 1. . Descriptive characteristics of Aboriginal and non-Aboriginal men and women (18–64 years of age) and boys and girls (2–17 years of age) in the 2004 Canadian Community Health Survey 2.2: Nutrition
inline image

The overall prevalence of obesity (BMI ≥ 30 kg/m2) in the total sample of adults was 22.9% (22.9% in men, 22.9% in women). The prevalence was higher among Aboriginal adults (37.8%), when compared to the rest of the population (22.6%). Similar trends of the higher prevalence of obesity among those indicating an Aboriginal ethnicity were observed when the sample was divided into men and women separately (Figure 1). The prevalence of obesity in the total sample of children and youth was 8.2% (9.2% in boys, 7.2% in girls). The prevalence was higher among Aboriginal children and youth (15.8%), when compared to the rest of the population (8.0%). Similar trends of the higher prevalence of obesity among those indicating an Aboriginal ethnicity were also observed when the sample was divided into boys and girls separately (Figure 1).

image

Figure 1. : Prevalence of measured overweight and obesity among non-Aboriginal and Aboriginal adults (18–64 years of age) and children and youth (2–17 years of age) in the 2004 Canadian Community Health Survey 2.2: Nutrition. E: coefficient of variation 16.6% and 33.3% (interpret with caution).

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Similar to the trends observed for obesity, the prevalence of measured overweight and obesity (BMI ≥ 25 kg/m2) was higher in adults indicating Aboriginal ethnicity. Overall, the prevalence of overweight and obesity was 57.7% in the total population (63.7% in men, 51.6% in women). The prevalence was higher among Aboriginal adults (68.8%) in comparison to the rest of the population (57.5%). As demonstrated in Figure 1, the prevalence of overweight and obesity was higher in men and women who indicated an Aboriginal ethnicity. The prevalence of overweight (including obesity) is also higher among children and youth indicating an Aboriginal ethnicity. The prevalence of overweight and obesity in the total sample of children and youth was 26.3% (27.0% in boys, 25.5% in girls). The prevalence was higher among Aboriginal children and youth (34.5%) in comparison to the rest of the population (26.1%). Similar trends of the higher prevalence of overweight and obesity among those indicating Aboriginal ethnicity were observed when the sample was divided into boys and girls (Figure 1).

The results of the logistic regression analyses predicting obesity among adults are presented in Table 2. After the inclusion of age and sex as covariates (Model 1), Aboriginal adults (OR = 2.4 (95% CI: 1.6–3.6)) had elevated odds for being obese. These results were largely unchanged after the addition of several covariates, including physical activity level (Models 2 and 3). Thus, the elevated risk for obesity associated with Aboriginal ethnicity was independent of the demographic and lifestyle variables included in the model. The odds for obesity were also higher among those who were physically inactive, independent of other variables in the model (OR = 2.0 (95% CI: 1.5–2.7)). An analysis of physical inactivity in the prediction of obesity was performed separately in the Aboriginal and non-Aboriginal samples. The odds ratios for obesity associated with physical inactivity were 2.0 (95% CI: 1.4–2.6) in the non-Aboriginal sample, and 3.0 (95% CI: 1.1–8.4) in the Aboriginal sample, after adjustment for age, sex, education, household income, and smoking.

Table 2. . Results of logistic regression analyses predicting obesity (BMI 30 kg/m2) from Aboriginal status and selected covariates among adults (18–64 years of age) in the 2004 Canadian Community Health Survey 2.2: Nutrition
inline image

The results of the logistic regression analyses predicting obesity in youth are presented in Table 3. After the inclusion of age (in years), sex and physical activity level as covariates, Aboriginal youth (OR = 2.3 (95% CI: 1.4–3.8)) had elevated odds for being obese.

Table 3. . Results of logistic regression analyses predicting obesity from Aboriginal status and selected covariates among youth (12–17 years of age) in the 2004 Canadian Community Health Survey 2.2: Nutrition
 OR95% CI
  • a

    Significantly different from reference category (P < 0.05).

Ethnicity  
    Non-Aboriginal1.0 
    Aboriginal2.3[1.4–3.8]a
Sex  
    Male1.0 
    Female0.7[0.6–1.0]a
Age  
    Per year1.0[0.9–1.1]
Physical activity level  
    Active1.0 
    Moderately active0.8[0.5–1.2]
    Inactive1.6[1.1–2.3]a

The overall prevalence of physical inactivity (<1.5 KKD) in the total sample of adults was 57.2% (55.7% in men, 58.7% in women). The prevalence was similar among Aboriginal adults and the rest of the population: 57.2% in non-Aboriginals and 58.3% in Aboriginals. There were no consistent associations between ethnicity and physical inactivity when the sample was divided to separate men and women (Figure 2a). However, within each ethnic group, the prevalence of physical inactivity was higher in women than in men. The overall prevalence of physical activity (≥3.0 KKD) in the total sample of adults was 17.7% (19.0% in men, 16.5% in women). There was no trend for physical activity across ethnic groups in adults: 17.7% in non-Aboriginals and 19.2% in Aboriginals (Figure 2b). A similar lack of trend was observed when the sample was divided into men and women; however, within each ethnic group, the prevalence of physical activity was higher in men than in women.

image

Figure 2. : Prevalence of (a) physical inactivity (<1.5 KKD) and (b) physical activity (≥3.0 KKD) among non-Aboriginal and Aboriginal adults in the 2004 Canadian Community Health Survey 2.2: Nutrition. E: coefficient of variation 16.6% and 33.3% (interpret with caution).

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The results of the logistic regression analyses predicting physical inactivity in adults are presented in Table 4. In contrast to the results for obesity, Aboriginal ethnicity was not a significant predictor of physical inactivity in this sample. However, being a daily smoker and being obese were both significantly associated with greater odds for being physically inactive, while higher education and income are both associated with lower odds for being physically inactive.

Table 4. . Results of logistic regression analyses predicting physical inactivity (<1.5 KKD) from Aboriginal status and selected covariates among adults (18–64 years of age) in the 2004 Canadian Community Health Survey 2.2: Nutrition
inline image

The prevalence of sedentary behavior (20+ h/week) among youth 12–17 years of age was 65.8% (71.7% in boys, 59.0% in girls). There were no consistent associations between ethnicity and the prevalence of sedentary behavior; however, within each ethnic group, boys reported consistently more sedentary behavior than girls.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References

The results of this study indicate a higher prevalence of overweight and obesity among Aboriginal peoples of Canada in comparison to the general Canadian population. Previous reports from smaller, non-representative regional studies have provided evidence of high levels of obesity in various Canadian Aboriginal groups (7,8,9,10,11,12,13). Further, one study using data from the 2000/01 and 2003 CCHS surveys showed that Aboriginal Canadians had the highest prevalence of self-reported obesity among all of the ethnic groups in Canada (6). While previous studies have been limited by their non-representative sample design or by the reliance on self-reported data, the current report provides the first evidence of a high prevalence of measured obesity among Aboriginal peoples of Canada using a representative population sample.

There are no comparable data on the prevalence of overweight and obesity among other contemporary representative samples of Aboriginal peoples in Canada using measured heights and weights. However, the 2002/03 First Nations Regional Longitudinal Health Survey collected data on self-reported heights and weights of ∼9,000 adults from 238 First Nations communities across Canada (29). Figure 3 presents the self-reported figures for the prevalence of overweight and obesity among adult participants in the 2004 CCHS 2.2: Nutrition and the First Nations RHS 2002/03. It should be noted that the Aboriginal participants in the CCHS 2.2: Nutrition, are representative of the off-reserve Aboriginal population, whereas the First National RHS 2002/03 collected data from the on-reserve First Nation population. The results suggest that the self-reported figures for prevalence of overweight and obesity are higher in both Aboriginal groups when compared with the general Canadian population, with the highest prevalence being found among the on-reserve population (73.6% in men, 72.3% in women).

image

Figure 3. : Prevalence of self-reported overweight and obesity (BMI ≥ 25 kg/m2) among non-Aboriginal and Aboriginal adults in the 2004 Canadian Community Health Survey 2.2: Nutrition and among First Nation (on-reserve) adults in the First Nations Regional Longitudinal Health Survey (RHS) 2002/03.

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The results of this study highlight the importance of physical activity in the prediction of obesity. In both youth and adults, physical inactivity was associated with increased odds for being obese, independent of age, sex, and ethnicity. In ethnic-specific analyses, the odds of being obese was higher among those who were physically inactive in both Aboriginal and non-Aboriginal adults. A recent regional study has shown an increased prevalence of metabolic syndrome associated with low physical activity and physical fitness among Aboriginal Canadians (17). Although these analyses are cross-sectional, taken together the results provide some evidence to suggest that physical activity is an important correlate of obesity and related co-morbidities in Aboriginal Canadians. Further research is needed to better delineate the dose–response relation between physical activity and health in Aboriginal groups to inform the development of physical activity interventions and recommendations for this population.

There are several strengths and limitations to this study that should be discussed. The strengths of the study include the large representative sample of the Canadian population, and the reliance on measured height and weight for the estimation of the figures for the prevalence of overweight and obesity. Although the CCHS 2.2: Nutrition is the largest contemporary representative sample of the Canadian population that includes measured heights and weights on a sizeable sample of Aboriginal Canadians, there are still limitations with respect to the sample size. As is evident from the results, when the sample was divided according to sex and ethnicity, some prevalence estimates had high coefficients of variation and should be interpreted with caution. Further, the data for physical activity and obesity used for these analyses were cross-sectional, and no cause-and-effect interpretations can be invoked.

The estimate of physical activity used in this study was based on self-reported participation in leisure-time physical activities over the previous 3 months. Self-reports of physical activity may be subject to bias, and do not take into account culturally diverse activities, such that responses to the questionnaire may vary across different ethnic groups. Thus, objective measures of physical activity such as pedometers or accelerometers would have increased the precision of physical activity measurement in this study. The reliance on leisure-time physical activity only may have masked important differences in overall physical activity levels between the Aboriginal and non-Aboriginal population. For example, there may be differences in occupational physical activity levels that may explain the differences observed in the figures for prevalence of overweight and obesity.

Sample size limitations necessitated collapsing both those who indicated they were Aboriginal-only and those of mixed-Aboriginal ancestry into the same group for analysis. Thus, questions regarding the effects of admixture on physical activity and obesity could not be investigated. Further, the sample sizes were too small to examine the prevalence figures of overweight and obesity among First Nation, Métis, and Inuit groups separately. Although the results show a high prevalence of overweight and obesity for Aboriginal people, the sample was limited to the off-reserve population. Limited data exist on measured heights and weights of the on-reserve Aboriginal population. The self-reported overweight and obesity data presented in this report suggest that the prevalence of overweight and obesity in the on-reserve population is at least as high as in the off-reserve population.

In summary, the prevalence of obesity is higher in Canadian Aboriginals compared to the rest of the population. Further investigation is required to better delineate the determinants of obesity and the associated health consequences in this population. Research with objective measures of physical activity is required, to better identify those aspects of physical activity that are most predictive of obesity. Ideally, studies that employ a longitudinal design should be used to examine the predictors of weight gain, obesity, and the co-morbidities of obesity among Aboriginal peoples. The results of this research will be useful in planning and designing intervention strategies targeted at the adoption and maintenance of healthy, physically active lifestyles for all Canadians.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References

Research support was provided by the First Nation and Inuit Health Branch of Health Canada. This research was also funded, in part, by a New Emerging Team grant from the Canadian Institutes for Health Research and the Heart and Stroke Foundation of Canada.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. DISCLOSURE
  8. Acknowledgments
  9. References
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