So What Causes Obesity In Manitoba?Thursday, October 27, 2011
Yesterday, I blogged about the rather weak relationship between BMI and health risks in the Manitoba Centre for Health Policy (MCHP) Report on Adult Obesity, and suggested that the results may have looked very different had the same data been analysed using the Edmonton Obesity Staging System.
Today, I want to address another interesting finding of this report, namely, the researcher’s attempts to identify the ’causes’ of obesity in Manitoba.
Variables examined included age, sex, marital status, education, employment, household income, activity restrictions, occupational physical activity, self-perceived life stress, satisfaction with life, self-rated mental health, sense of community, eating fruits and vegetables, physical activity leisure and travel, sedentary activities, current smoking, binge drinking, recent changes to improve health, food insecurity, and regular doctor.
Among these, location of residence, age, sex, education, employment, and marital status were particularly strong predictors of excess weight.
Interestingly, the psychological variables had little additional ‘effect’.
leisure– and travel–time activity level was the most strongly associated variable and showed a dose–response relationship—higher levels of activity were associated with lower likelihood of obesity. Other important variables were smoking (which was associated with a lower likelihood of obesity) and time spent in sedentary activities (more than 30 hours per week was associated with a higher likelihood of obesity).
Notably, only age and geography were significantly related to BMI values in youth.
Apart from the fact that such analyses cannot actually prove ‘causality’ as they are merely associated and therefore assumptions about modifying any of the modifiable variable will in fact reduce BMI, the researcher also made another notable observation:
“It is important to note that despite including many variables, this study was only able to explain a small amount of why people are obese. This means there are other reasons for the recent rises in weight, perhaps changes in our diets or our physical and social environment.”
Indeed, I would easily have predicted that factors not considered in this analysis, including parental BMI, birth weight, maternal weight at inception and birth of the participant, duration of sleep, etc. may well have accounted for some of the increase in obesity.
This should not detract from the importance of factors like sedentariness, stress, food insecurity and other variables that had some influence on obesity rates in this study.
It should, however, make us cautious in accepting the commonly held notion that the ‘root cause’ of obesity is simply increased sedentariness and eating too much.
Clearly, this is not the whole (and perhaps not even the biggest part) of this ‘story’.