Abstract

Objective To study the impact of body mass index (BMI) SD score (SDS) improvement through lifestyle modification on metabolic risk and body composition over 12 months.

Design Prospective cohort study.

Setting Hospital outpatient weight management clinic in the UK.

Patients 88 adolescents (40 males, 86% Caucasian) of median age 12.4 years (range 9.1–17.4) and mean (SD) BMI SDS 3.23 (0.49).

Main outcome measures BMI at baseline and 12 months 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 (BP) were measured.

Results Reducing BMI SDS by ≥0.5 achieved significant improvements in important measures of body composition with mean waist circumference SDS reducing by 0.74 units and body fat SDS by 0.60 units, while also leading to significant reductions in key metabolic risk factors (triglycerides (−30%), low-density lipoprotein-cholesterol (−15%), HsCRP (−45%)). A lesser reduction of ≥0.25 improved insulin sensitivity, total cholesterol/high-density lipoprotein ratio and BP. The greater the BMI SDS reduction, the better the improvement seen in insulin sensitivity. The most insulinsensitive individuals at baseline were most likely to achieve BMI SDS changes of ≥0.5 regardless of baseline BMI SDS.

Conclusions Improvement in body composition and cardiometabolic risk can be seen with BMI SDS reductions of ≥0.25 in obese adolescents, while greater benefits accrue from losing at least 0.5 BMI SDS. The most insulin-sensitive individuals seem best able to effect these changes.