Objective: To study the impact of Body Mass Index (BMI) Standard Deviation Score (SDS) improvement through lifestyle modification on metabolic risk and body composition over twelve months.
Design: Prospective cohort study
Setting: Hospital out-patient weight management clinic in UK.
Patients: Eighty eight adolescents (40 male, 86% Caucasian) of median age 12.4 years (range 9.1-17.4) and mean (standard deviation) BMI SDS 3.23 (0.49).
Main outcome measures: Baseline and 12-months. Weight and height used to derive BMI as kg/m2. BMI was adjusted for age and gender providing BMI SDS using British 1990 Growth Reference Data. Body composition was measured by bioimpedance. A standard oral glucose tolerance test (OGTT) examined glucose metabolism. Fasting lipid profiles, High Sensitivity 'C' Reactive Protein (HsCRP) and blood pressure were taken.
Results: Reducing BMI SDS by ≥0.5 achieved significant improvements in important measures of body composition: mean waist circumference SDS reducing by 0.74 units and body fat SDS by 0.60 units, whilst also leading to significant reductions in key metabolic risk factors (triglycerides [-30%], LDL-Cholesterol [-15%], HsCRP [-45%]). A lesser reduction of ≥0.25 improved insulin sensitivity, total cholesterol/HDL ratio and blood pressure. The greater the BMI SDS reduction, the better the improvement seen in insulin sensitivity. The most insulin sensitive individuals at baseline were most likely to achieve BMI SDS changes ≥0.5 regardless of baseline BMI SDS.
Conclusions: Improvement in body composition and cardio-metabolic risk can be seen with BMI SDS reductions of ≥0.25 in obese adolescents whilst greater benefits accrue from losing at least 0.5 BMI SDS. The most insulin sensitive individuals seem best able to effect these changes.