Effect of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on insulin sensitivity in participants with type 2 diabetes mellitus (T2DM): A systematic review and meta-analysis of randomised controlled trials

<ns3:p> Background High-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) are widely prescribed exercise modalities for individuals with type 2 diabetes mellitus (T2DM). However, their comparative effects on insulin sensitivity remain unclear. Objective To compare the effects of HIIT and MICT on insulin sensitivity and related metabolic outcomes in adults with T2DM. Methods A systematic review and meta-analysis of randomised controlled trials (RCTs) was conducted following PRISMA guidelines and registered with PROSPERO (CRD42024593995). Seven databases (CINAHL Plus, EMBASE, MEDLINE, ProQuest, SCOPUS, SPORT Discus, and Web of Science) were searched from January 2015 to December 2025. Eligible RCTs included adults aged 30–70 years with T2DM comparing HIIT, MICT, and/or non-exercise control groups. The revised Cochrane Risk of Bias tool (RoB 2) and modified Downs and Black checklist were used to assess study quality. Data were pooled using random-effects meta-analysis and reported as standardised mean differences (SMD) with 95% confidence intervals (CI). Results Four RCTs (n = 162; 66 HIIT, 63 MICT, 39 control) met the inclusion criteria. Meta-analyses revealed no statistically significant between-group differences in post-intervention outcomes: HbA1c (SMD −0.52 [95% CI −2.73 to 1.69], p = 0.42), HOMA-IR (SMD −0.14 [95% CI −3.32 to 3.04], p = 0.67), fasting insulin (SMD −0.05 [95% CI −4.30 to 4.21], p = 0.91), fasting blood sugar (SMD −0.29 [95% CI −1.32 to 0.75], p = 0.18), and body mass index (SMD −0.37 [95% CI −1.23 to 0.50], p = 0.27). Heterogeneity was moderate to high for some outcomes (I <ns3:sup>2</ns3:sup> = 42–84%). Overall methodological quality was good-to-excellent across studies. Conclusions HIIT and MICT appear to elicit comparable improvements in insulin sensitivity among adults with T2DM. These findings support flexibility in exercise prescription to accommodate individual preferences and clinical contexts. Larger, standardised RCTs are needed to confirm these results and explore long-term adherence and metabolic outcomes. <ns3:bold>Systematic review registration:</ns3:bold> PROSPERO CRD42024593995. </ns3:p>