Objective: Metabolic dysfunction characterized by insulin resistance (IR) is an important risk factor for type-2 diabetes and coronary artery disease (CAD). The aim of this study was to determine if clinical lifestyle interventions differing in scope and intensity improve IR, defined by the lipoprotein IR (LPIR) score, in individuals differing in the severity of metabolic dysfunction.
Methods: Subjects with diagnosed type-2 diabetes, CAD or significant risk factors participated in one of two clinical lifestyle modification interventions: (i) intensive non-randomized programme with a strict vegetarian diet (n = 90 participants, 90 matched controls) or (ii) moderate randomized trial following a Mediterranean-style diet (n = 89 subjects, 58 controls). On-treatment and intention-to-treat analyses assessed changes over 1 year in LPIR, lipoprotein profiles and metabolic risk factors in intervention participants and controls in both programmes.
Results: In the on-treatment analysis, both interventions led to weight loss: [-8.9% (95% CI, -10.3 to -7.4), intensive programme; -2.8% (95% CI, -3.8 to -1.9), moderate programme; adjusted P < 0.001] and a decrease in the LPIR score [-13.3% (95% CI, -18.2 to -8.3), intensive; -8.8% (95% CI, -12.9 to -4.7), moderate; adjusted P < 0.01] compared with respective controls. Of the six lipoprotein parameters comprising LPIR, only large very-low-density lipoprotein particle concentrations decreased significantly in participants compared with controls in both programmes [-26.3% (95% CI, -43.0 to -9.6), intensive; -14.2% (95% CI, -27.4 to -1.0), moderate; P < 0.05]. Intention-to-treat analysis confirmed and strengthened the primary results.
Conclusion: A stringent lifestyle modification intervention with a vegetarian diet and a moderate lifestyle modification intervention following a Mediterranean diet were both effective for improving IR defined by the LPIR score.
Keywords: Insulin resistance; lifestyle modification; lipoproteins; weight loss.