Figure 2.
Insulin sensitivity decreases with increasing BMI. Following an overnight fast, participants (N = 36) consumed a mixed meal comprising 35% of the individual’s total daily energy expenditure. Blood samples were collected for the assessment of (A) glucose, (B) insulin, (C) C-peptide, and (L) triglycerides prior to meal ingestion, upon completion of the mixed meal (time = 0), and at scheduled intervals over the subsequent 5 h. (D) Insulin sensitivity (SI; N = 33), (E–H) β-cell responsivity (Φ; N = 30), and (I–K) disposition index (DI; N = 30) were calculated using the oral glucose and c-peptide minimal models. M: the postprandial incremental area under the curve of circulating triglycerides (iAUC; N = 36) and (N) the absolute change in triglycerides from baseline to peak triglyceride concentration (ΔTG; N = 36) were calculated. Bar graphs are presented as mean and SD. Black circles: females; white squares: males. *Significant difference between participants with BMI < 30 kg/m2 and those with BMI > 30 kg/m2, as determined by unpaired t tests or Wilcoxon Signed-Ranks tests. Correlations with BMI were assessed for each variable and are presented as lines of best fit with 95% confidence intervals. The r and P values represent the bivariate correlation coefficients. BMI, body mass index; DID, dynamic disposition index; DIS, static disposition index; DITotal, total disposition index; iAUC, triglyceride incremental area under the curve; SI, insulin sensitivity; TG, triglyceride; ΦB, basal β-cell responsivity; ΦD, dynamic β-cell responsivity; ΦS, static β-cell responsivity; ΦTotal, total β-cell responsivity; ΔTG, absolute change in triglycerides.