Threshold for improvement in insulin sensitivity with adolescent weight loss

Abstract

Objectives: To assess the association of weight loss and insulin sensitivity, glucose tolerance, and metabolic syndrome (MS) in obese adolescents following weight loss treatment, and to determine the threshold amount of weight loss required to observe improvements in these measures.

Study design: A randomized, controlled behavioral weight loss trial was conducted with 113 obese adolescents. Changes in fasting insulin, homeostasis model assessment of insulin resistance, whole body insulin sensitivity index (WBISI), body mass index (BMI), and MS criteria were assessed at baseline and at month 4.

Results: There was significant improvement in all measures of insulin sensitivity at month 4. Mean fasting insulin dropped from 22.3 to 16.6 μU/mL (P < .0001). Homeostasis model assessment of insulin resistance decreased significantly from 4.9 to 3.7 (P = .001) and WBISI increased significantly from 2.87 to 3.98 (P < .0001). An 8% reduction in BMI led to a significant improvement in WBISI (P = .03) and was the optimal threshold. Fewer individuals met criteria for MS after weight loss (P = .0038), although there were no significant changes in the individual features of the syndrome.

Conclusions: In this trial, weight loss at month 4 was associated with improved insulin sensitivity in obese adolescents. An approximate decrease in BMI of 8% was the threshold level at which insulin sensitivity improved. As more weight loss programs are designed for obese adolescents, it will be important to have reasonable weight loss goals that will yield improvements in metabolic and cardiovascular disease risk factors.

Keywords: BMI; Body mass index; CD; Conventional diet; HDL; HOMA-IR; High-density lipoprotein; Homeostasis model assessment of insulin resistance; MS; Metabolic syndrome; OGTT; Oral glucose tolerance test; WBISI; Whole body insulin sensitivity index.

Figure 1

Each BMI threshold represents the entire population with evaluable WBISI at both timepoints (N=72), divided between those who lost less than that percent of their BMI and those who lost more than that percent of their BMI. * represents a significant difference in change in WBISI between the two groups (p<0.05)

Figure 2

We categorized MS Status as Resolved (N=5), Developed (N=4), or Unchanged (N=82; those who either started and finished the trial with MS, or those who started and finished the trial without MS). 91 subjects had complete MS data at both timepoints. Kruskal-Wallis analysis between all three groups p=0.29. Kruskal-Wallis analysis between those whose MS resolved and those who developed MS p=0.05.