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Obesity in Canadian children
CMAJ 2001;164(11):1563 [PDF]

See response from: M. Tremblay, J.D. Willms; R. Andersen
Your excellent articles on obesity in Canadian children ignored caloric intake as the major factor in this problem [Research],1 [Editorial].2 Canadians obviously have a sedentary lifestyle. Like Ross Andersen,2 we decry the decline in physical education in our school system because early habits form lifelong patterns of behaviour. However, the exercise factor must pale when compared with the massive caloric intake we "enjoy" in Canada. Although regular physical activity is an integral component of a healthy lifestyle, it is much less effective than dietary caloric restriction in helping to maintain a negative energy balance and lose weight. We are not far behind the world-leading Danes in terms of the amount of food we consume (3780 cal/d v. 2921 cal/d).

Consistent with trends in overweight and obesity, most data suggest that energy intake has increased over the past several decades and is a major contributor to the increase in average body weight. Beginning in childhood, we eat more frequently, we eat to the point of saturation and we eat more calorie-dense foods.

A recent study concluded that energy availability increased by 15% between 1970 and 1994, on the basis of per capita energy-availability estimates from the US Department of Agriculture.3 The study also found that Americans are eating more meals outside the home, relying more heavily on convenience foods and consuming larger portions. When caloric intake is being determined, frequency of eating, the caloric density of the food and the quantity of food eaten must be considered.

Caloric restriction reduces oxidative DNA damage,4 and overeating may underlie this society's epidemic of cancer.5 Other pandemic diseases of Western society, such as stroke and heart disease, are also affected by caloric intake. Although exercise and caloric intake both affect health, increasing caloric intake is probably the more serious public health problem.

Roland Auer
Department of Pathology and Laboratory Medicine
University of Calgary
Calgary, Alta.
David Lau
Departments of Medicine and of
   Biochemistry and Molecular Biology
University of Calgary
Calgary, Alta.
Raylene Reimer
Departments of Kinesiology and of
   Biochemistry and Molecular Biology
University of Calgary
Calgary, Alta.


    1.   Tremblay MS, Willms JD. Secular trends in the body mass index of Canadian children [published erratum appears in CMAJ 2001;164(7):970]. CMAJ 2000;163(11):1429-33.
    2.   Andersen RE. The spread of the childhood obesity epidemic [editorial]. CMAJ 2000;163(11):1461-2.
    3.   Harnack L, Jeffery R, Boutelle K. Temporal trends in energy intake in the United States: a perspective. Am J Clin Nutr 2000;71:1478-84. [MEDLINE]
    4.   Gao P, Chou MW. Effect of caloric restriction on hepatic nuclear DNA damage in male Fischer 344 rats with aflatoxin B1. Toxicol Lett 1992;61:233-42. [MEDLINE]
    5.   Albanes D. Total calories, body weight, and tumor incidence in mice. Cancer Res 1987;47:1987-92. [MEDLINE]



Copyright 2001 Canadian Medical Association or its licensors