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Children, Obesity and a Weight Loss Update
In a study published in March by Andy Ness, Ph.D., of the University of Bristol (England) researchers have almost concluded that increased physical activity in children decreases their risk of becoming overweight. Almost, you wonder, what in the heck can she mean by that?In a cross-sectional study of more than 5,000 12-year-olds, a daily fifteen minutes of moderate to vigorous exercise was associated with a 50% drop in the risk of obesity for boys and a 40% decline in risk for girls. "The association between physical activity and obesity we observed was strong," Dr. Ness said. "These associations suggest that modest increases in physical activity could lead to important reductions in childhood obesity."
The study is one part of a research project called the Avon Longitudinal Study, which enrolled 14,000 pregnant women in England in 1991 and 1992 and has followed these women and their children since that time. Children in the study wore equipment that measured their physical activity and the researchers calculated their body-mass index (BMI) using standard tools; they also measured fat and lean mass using dual energy x-ray absorptiometry scanning (I don't know either - but I'd guess that it's some fancy research tool that gives an accurate assessment of body fat and muscle). The point is of all this is that this study is the first of its kind to use objective measures of physical activity and the body's fat and lean muscle masses.
So what's the "maybe" about? Well first, studies have limitations; in this case the study involves a cross-section of a population, a brief picture of a group at a certain point in time. As such, the researchers can't say for certain that exercise reduces obesity risk, because they can't say for certain that the opposite is also not true. In this case it could be hypothesized that obesity causes a decrease in physical activity.
A second limitation of this study is that it is observational. The purpose of an observational study is to draw from your observations to create a hypothesis (scientific guess) about the possible effects of a treatment on your subjects, in this study the hypothesis is that exercise decreases the risk that a child will become overweight.
The authors conclude their analysis with the obligatory statement that their hypothesis will now need further study under controlled conditions, to prove the connection between exercise and reduced obesity risk in children. I would also add that they failed to note a third technical limitation of their study: that they only studied 12-year olds; therefore, they cannot automatically conclude that increased physical activity will decrease obesity risk in younger or older children.
Some of you may remember that at about this time last year I embarked on a weight loss plan of my own. On the downhill side of 45, I was getting concerned that I would look like a tea pot by the time I turned 50 (can you say central obesity three times fast??). Well I'm happy to report that regular moderate exercise has certainly helped me to lose weight; as of my recent 48th birthday I have lost a total of 13 pounds and I'm eating whatever I want-in smaller portions. I have set a goal of another 5 pounds and I'll be ecstatic and lower my risk of obesity.
Take care, Laurie
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