Exercise in Young Obese Children Reduces BP, Improves Markers of Atherosclerosis

December 14, 2009

December 14, 2009 (Geneva, Switzerland)A program of regular physical exercise--one hour three times a week--resulted in significant improvements in blood pressure, total body fat, and markers of atherosclerosis in a small study of obese children aged six to 11 reported online December 11, 2009 in the Journal of the American College of Cardiology [1].

Lead author, pediatrician Dr Nathalie Farpour-Lambert (University Hospitals of Geneva, Switzerland), told heartwire : "What's new about this study is that we did an intervention in really young kids, with an average age of just under nine, and we didn't talk about food or nutrition at all." Not everyone realizes that obese children develop the signs of atherosclerosis and high blood pressure very early, she says, "and physical activity is not usually viewed as a treatment in children. Yet the changes we obtained with this simple exercise program--which was nothing fancy, just kids having fun and being with their friends--were close to what has been seen with very intensive multidisciplinary programs."

The changes we obtained with this simple exercise program . . . . were close to what has been seen with very intensive multidisciplinary programs.

The fact the children really enjoyed themselves was key, she notes: "The kids loved it; we had a really good response with no dropouts, which is very important. Many of these children become excluded very quickly from mainstream activities, so they lose their physical capacity and have low self-esteem and instead spend time at home on sedentary activities, which are coupled with increased food intake."

In an accompanying editorial [2], Dr David S Celemajer (Royal Prince Alfred Hospital, Camperdown, Australia) says that the Swiss study "provides novel information [and] showed that achievable physical activity could reduce BP, arterial stiffness, and abdominal fat . . . extending our knowledge about potential cardiovascular benefits in obese children."

Hypertension Reduced by 29% After Six Months

Farpour-Lambert and colleagues recruited 44 Swiss children aged 6 to 11 with body-mass index (BMI) over the 97th age- and sex-specific percentile and randomized them to three months of exercise training after school or usual exercise patterns, which meant the latter group was relatively inactive. The modified crossover design meant that, after the first three months, both groups of children were offered the chance to participate in the exercise training for a further three months.

The one-hour activities included ball games, swimming, and running and were structured to include 30 minutes of aerobic work, followed by 20 minutes of strength work and 10 minutes of stretching.

Changes were assessed at three and six months and included 24-hour BP, arterial intima-media thickness (IMT) and stiffness measured by ultrasound, endothelial function measured by flow-mediated dilation, BMI, body fat (calculated using the "gold-standard" dual-energy X-ray absorptiometry [DXA]), cardiorespiratory fitness determined by maximal oxygen consumption (VO2max), physical activity, and biological markers.

Changes in BP, Cardiorespiratory Fitness, and Arterial Function Parameters During the Three-Month Exercise Program (Intention-to-Treat Analysis)

Parameters Exercise (n=22) Control (n=22) Treatment effect* p
24-h SBP, mm Hg -6.9 3.8 -10.7 0.007
24-h DBP, mm Hg -2.6 -0.2 -2.3 0.3
Cardiorespiratory fitness, VO2max (mL x kg-1 x min-1 ) 1.9 -1.6 3.5 0.007
IMT of CCA (mm x 10-2) -0.09 1.13 -1.22 0.2
Arterial stiffness, Einc (mm Hg x10-2) 1.81 -0.54 2.34 0.4
FMD, % -0.59 0.13 -0.72 0.4
*Results are shown as mean. Treatment effect defined as change in the obese exercise group compared with the control group.

SBP=systolic blood pressure; DBP=diastolic blood pressure; IMT= intima-media thickness; CCA=common carotid artery; Einc=incremental elastic modulus; FMD=flow-mediated dilation

"We reduced the prevalence of hypertension by 12% at three months and by 29% at six months; we also saw reductions in arterial stiffness at six months and stabilization of arterial IMT on ultrasound in the active group, whereas the control group had some reverse changes," Farpour-Lambert said.

The changes in BP were of greater magnitude in hypertensive subjects and independent of body-fat reduction, the researchers note. "We also show that our exercise intervention has beneficial effects on whole-body and abdominal fat, fat-free mass, and cardiorespiratory fitness in obese children," they observe, although they point out that the exercise did not seem to have an effect on endothelial- or smooth-muscle-cell function.

Benefits "Striking and Significant"

"The children attended over 80% of the scheduled sessions, and the benefits were striking and significant," says Celemajer in his editorial.

But he draws attention to what he says is a "key observation"--that BMI did not change in the exercise group, because the approximate 2% loss of body fat was offset by a 1.2-kg gain in fat-free mass. "Thus, clinical exercise programs in children should monitor percent body fat rather than BMI. Waist circumference, for example, is a simple parameter to measure, although DXA scans provide better direct measures of obesity and location."

For children, exercise needs to be enjoyable and appealing because the effort needs to be sustained.

Celemajer says one of the limitations of this study was that the mechanism of benefit was not specifically assessed, and understanding this "is of practical as well as academic interest."

For example, a study published earlier this year illustrated that antioxidant vitamin supplementation revoked exercise-induced benefits on insulin sensitivity [3], he notes.

"Much work remains to optimize recommendations for exercise activities in children, both healthy and overweight/obese. For children, exercise needs to be enjoyable and appealing because the effort needs to be sustained, especially in an environment where entertaining sedentary opportunities abound." This work by Farpour-Lambert et al "has given us motivation to progress along this challenging trail," he concludes.

Farpour-Lambert agrees: "While we didn't assess quality of life, the children had fun and they kept in touch after the intervention," she told heartwire .

The study was supported by the Swiss National Science Foundation and the Geneva University Hospitals Research and Development Fund.

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