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Study Identifies ‘Pre-Obese’ Children, Based On Activity Levels

Even when still growing and developing, eight, nine and 10 year old children do not have excess body fat, they may lack sufficient daily physical exercise. This lack of physical activity is a significant predictor that they will develop increasing levels of body fat over time, according to University of Manitoba researcher Dr. Rebecca Mollard, speaking on April 30 at Experimental Biology 2007 in Washington, DC.  

In a three year longitudinal study of 41 children, the researchers found that 74 percent of children at year one and 43 percent of children at year two who did not have excess body fat and were not overweight were still below the recommended level of physical activity. Because these “pre-obese” children are not yet overweight, and because they may even increase exercise levels modestly as part of their natural developmental sequence (although still remaining well below recommendations), these pre-obese children may not be perceived at risk for obesity, says Dr. Mollard. This means that the opportunity for simple primary prevention may be missed. 

Dr. Mollard is a postdoctoral fellow in the laboratory of Dr. Dean Kriellaars. Her Experimental Biology presentation, made jointly with doctoral student Kristy Wittmeier and Dr. Kriellaars, is part of the scientific program of The American Physiological Society. 

Reduction in physical activity is widely believed to explain part, if not most, of the alarming increase in the number of overweight and obese children in numerous countries worldwide over the past two decades. The study reported at Experimental Biology is part of a larger cross-sectional study of 251 children, looking at the relationship between body composition, cardiovascular fitness, physical activity and daily physical education in schools. In this component of the study, researchers followed a subset of these children for three years, beginning when they were eight years old, to determine how body composition and physical activity change over time.Body fat and body mass index (BMI) were measured after one and two year periods, along with a direct measure of physical activity, avoiding the problems with self-report of physical activity.

Although Canadian and U.S. health agencies recommend that children engage in a minimum of 60 minutes of moderate or above physical exercise per day, the study found that only 16.4 percent met the 60 minute guidelines. Only an extra 30 minutes of physical activity equivalent to a brisk walk - equaling approximately 110 calories per day - would be enough to substantively affect the caloric balance and body composition over the three-year period.  

Dr. Mollard says these findings are consistent with the larger study, which indicates that the likelihood of having higher amounts of body fat are significantly reduced with higher levels of moderate (45 minutes per day) or vigorous (15 minutes per day) activity. Children who achieved higher amounts of physical activity accumulated lower amounts of body fat over time. To achieve protection from developing excess body fat, the children would need to add approximately 30 minutes per day of exercise the equivalent of brisk walking. 

Funding for this study was provided by the Government of Manitoba. Dr. Mollard and Ms. Wittmeier are supported by fellowships from the Manitoba Institute of Child Health.

Physiology is the study of how molecules, cells, tissues and organs function in health and disease. Established in 1887, the American Physiological Society (APS) was the first U.S. society in the biomedical sciences field. The Society represents more than 10,500 members and publishes 15 peer-reviewed journals with a worldwide readership.