BOSTON — Participation in a structured lifestyle and exercise intervention can significantly improve the metabolic parameters of obese children with high insulin sensitivity, according to findings of a study presented at the Fifth Annual World Congress on the Insulin Resistance Syndrome.
Dr. Radhika Purushothaman of the Infants' and Children's Hospital of Brooklyn (N.Y.) at Maimonides and her colleagues enrolled 128 healthy seventh-grade students into a 12-week randomized controlled trial: 24 of the students were randomized to a lifestyle-only intervention, which focused primarily on dietary modification; 58 were randomized to a lifestyle plus exercise intervention; and 46 were in a control group with no intervention. The lifestyle plus exercise group was further subdivided according to body mass index (BMI) percentile: 28 students were in the lean group (BMI less than 85%), 8 were in the overweight group (BMI between 85% and 95%), and 22 were in the obese group (BMI greater than 95%). The weight categories in this study differ from those of the Centers for Disease Control and Prevention.
Because of the small number of children in the overweight subgroup, they were not included in the final subgroup comparison.
The investigators measured clinical and biochemical parameters including height, weight, blood pressure, body fat percentage, waist circumference, lipid profile, glucose tolerance via intravenous glucose tolerance test, insulinlike growth factor binding protein-I (IGFBP-1), baseline adiponectin level, acute insulin response, quantitative insulin sensitivity check index (QUICKI), and glucose disposition index.
An assessment of the BMI subgroups of the lifestyle and exercise intervention group showed the most interesting findings. Post intervention, both subgroups demonstrated increased BMI and decreased blood pressure. Within the obese group, higher insulin sensitivity at baseline was associated with more significant loss of visceral fat, said Dr. Purushothaman.
The lean subgroup had—at baseline and post intervention—a lower percent body fat, waist circumference, systolic blood pressure, fasting insulin and acute insulin response, and a higher adiponectin level than the obese group. Relative to the obese group, the lean group showed improvements in body fat percentage, blood pressure, IGFBP-1, acute insulin response, and glucose disposition index.
The results showed a significant negative correlation between fasting insulin at baseline and change in waist circumference after intervention in the obese group, and a significant positive correlation between the change in waist circumference and adiponectin and IGFBP-1 in the lean group.
Given the variations in intervention response observed between lean and obese children, the investigators concluded that exercise and lifestyle interventions should be different in these subgroups of children, with obese children requiring more intensive intervention with specifically modified diet, Dr. Purushothaman reported.
The data also suggest that improvement in biochemical parameters can occur even before changes in BMI, and they may be associated with a decrease in body fat percentage, Dr. Purushothaman stated.
She noted that longer term follow-up is needed to determine if the metabolic changes are sustainable and whether obese children will start showing improvement with longer periods of intervention.
In terms of the larger groups, there was no difference at baseline across the three groups in BMI, percentage body fat, waist circumference, lipid profile, adiponectin, acute insulin response, IGFBP-1, QUICKI, and glucose disposition index, Dr. Purushothaman reported.
After 12 weeks, the glucose disposition index improved significantly in both intervention groups. The lifestyle plus exercise intervention was associated with increases in acute insulin response and BMI and decreases in body fat, while both intervention groups showed decreases in adiponectin and IGFBP-1.