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Obesity in Canadian children
CMAJ 2001;164(11):1565 [PDF]

In response to: R. Auer, et al
Roland Auer and colleagues assert that when attempting to explain the current increase in the prevalence of obesity, "the exercise factor must pale when compared with the massive caloric intake we 'enjoy' in Canada." Excess energy intake is no doubt a contributing factor to the increasing girth of Canadian youth. However, to contend that the increasing prevalence of obesity is solely due to gluttony may oversimplify this complex problem [Editorial].1 For example, Prentice and Jebb reported that the prevalence of obesity doubled from 1980 to 1990 in Britain.2 During this time, energy intake declined substantially; the implication is that levels of physical activity, and hence energy needs, declined even faster. Interestingly, these authors reported that the changing prevalence of obesity was tightly related to sedentariness, hours of television watched and the number of cars per household; they concluded that inactive lifestyles are at least as important as diet in causing obesity, and possibly represent the dominant factor.2 Physical inactivity also may be a cue for eating in some children. My colleagues and I recently reported that US children who watch 5 or more hours of television per day consume 175 kcal/d more than those who watch at most 1 hour per day.3

Auer and colleagues also note that chronic caloric restriction has been demonstrated to increase longevity in other species. Translating findings in animal models to humans remains problematic. Most people have difficulty maintaining even a moderately restricted diet for any length of time.

Physicians must understand that obesity is caused by a complex interaction of genetics, diet, activity levels and behaviours. Long-term weight management will likely be achieved in overweight patients who learn to set realistic goals, change the behaviours that have led them to become overweight, increase their levels of physical activity and simultaneously engage in sound dietary practices.

Ross Andersen
Division of Geriatric Medicine and Gerontology
School of Medicine
Johns Hopkins University
Baltimore, Md.


    1.   Andersen RE. The spread of the childhood obesity epidemic [editorial]. CMAJ 2000;163(11):1461-2.
    2.   Prentice AM, Jebb SA. Obesity in Britain: gluttony or sloth? BMJ 1995;311:437-9. [MEDLINE]
    3.   Crespo CJ, Smit E, Troiano RP, Bartlett SJ, Macera CA, Andersen RE. Television watching, energy intake, and obesity in U.S. children: results from the Third National Health and Nutrition Examination Survey, 1988-1994. Arch Pediatr Adolesc Med 2001;155:360-5. [MEDLINE]



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