Academic journal article Canadian Journal of Public Health

Physical Activity, Cardiorespiratory Fitness and Body Mass Index as Predictors of Substantial Weight Gain and Obesity

Academic journal article Canadian Journal of Public Health

Physical Activity, Cardiorespiratory Fitness and Body Mass Index as Predictors of Substantial Weight Gain and Obesity

Article excerpt

The Canadian Physical Activity Longitudinal Study

ABSTRACT

Background: Obesity is a growing health issue in Canada and the identification of the determinants of obesity is important for the development of prevention strategies. The purpose of this investigation was to determine the relationships between physical activity, cardiorespiratory fitness, body mass index (BMI), and the development of future obesity.

Methods: The sample included 459 adults (18+ y; 223 men, 236 women) from the Canadian Physical Activity Longitudinal Study (PALS; 2002-04). Data on physical activity, smoking, alcohol consumption, BMI, and cardiorespiratory fitness (VO^sub 2max^) were collected in 1981 and 1988. The mean BMI, physical activity, and VO^sub 2max^ were calculated across the 1981 and 1988 measures. Self-reported height and weight were collected in the 2002-04 survey, and participants were classified as overweight (BMI 25 to 29.9 kg/m^sup 2^) or obese (BMI ≥30 kg/m^sup 2^). Logistic regression was used to predict overweight, obesity or substantial weight gain (10 kg or more) in 2002-04, controlling for age, sex, smoking and alcohol use.

Results: Higher VO^sub 2max^ in 1981-88 was associated with lower odds of obesity in 2002-04 (OR=0.87; 95% CI: 0.76-0.99, p<0.05), and higher BMI in 1981-88 was associated with higher odds of obesity in 2002-04 (1.84; 1.52-2.20, p<0.0001). In women, higher VO^sub 2max^ (0.82; 0.72-0.93) resulted in lower odds of a 10 kg weight gain.

Conclusions: The results indicate that cardiorespiratory fitness and previous BMI are important predictors of future weight gain and obesity, and should be incorporated in strategies to identify individuals at increased risk of obesity.

MeSH terms: Obesity; weight gain; body mass index; physical fitness; longitudinal survey

The prevalence of obesity among Canadians is increasing. The average body mass index (BMI; kg/m^sup 2^) of adults has increased from approximately 25 to 27 between 1978-79 and 2004, while the prevalence of obesity (BMI ≥30.0 kg/m^sup 2^) has increased from 13.8% to 23.1% over the same period.1 These changes in obesity are placing an increasing burden on medical care and are taking a toll on public health.2,3

As obesity becomes a growing health issue, it is important that the determinants and correlates of unhealthy body weights in the Canadian context be identified in order to develop appropriate prevention strategies. The increase in obesity is due for the most part to an energy imbalance where the amount of energy being consumed by an individual is greater than the amount of energy being expended.4 Although an inverse relationship between leisure time physical activity and obesity has been demonstrated,5,6 it remains to be determined whether physical activity prevents the development of obesity. It is likely that among those who do not match food consumption to low activity levels, the constant energy imbalance leads to weight gain. Thus, we hypothesize that those who are physically inactive are more likely to be overweight or obese later in life.

Physical activity is a behaviour which is difficult to measure and is often misreported. On the other hand, physical fitness, a physiologic condition that reflects habitual physical activity levels,7 can be objectively measured. Thus, the purpose of this investigation was to determine the relationships between physical activity, cardiorespiratory fitness and the development of overweight and obesity over 20 years in a prospective cohort of Canadians. Given that indicators of obesity are relatively stable traits over time/ we also hypothesized that BMI would also predict the development of obesity.

METHODS

Data source

The Physical Activity Longitudinal Study (PALS) is a 20-year follow-up study of people who originally participated in the 1981 Canada Fitness Survey (CFS) and the 1988 Campbell's Survey of Well Being in Canada (CSWB). …

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