It's been estimated that as many as 20% of children in the United States are overweight or obese, and parents may be confused as to the best way to help their child remain or attain a healthy and normal weight.

In a study published in the American Journal of Clinical Nutrition, Australian researchers studied 106 6- to 9-year-olds to determine how much energy they expended, whether their energy expenditure was related to physical activity, and whether there was a relationship between their physical activity and their body fat percentages. The researchers visited the children's homes and taught them to use a specialized technique for measuring energy output over 10 days. The children's height and weight were measured, and body mass index was calculated. The percentage of body fat and muscle mass in the children was also calculated, and differences between boys and girls were evaluated.

Both boys and girls got less exercise than recommended by national standards. With respect to weight, height, and body mass index (BMI), boys did not differ significantly from girls. Girls had significantly higher measurements of fat mass and percentage of body fat, and boys had higher measurements of muscle mass. In boys but not girls, more physical activity meant a lower BMI, percentage of body fat, and fat mass. These findings suggest that lower physical activity levels may contribute to the rise in prevalence of childhood obesity, especially in boys.

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