Objectives: To explore the impact of uninterrupted sitting versus sitting with resistance-type activity breaks on adolescents' postprandial glucose responses while consuming a diet varying in energy. Design: Cross-over randomised trial. Methods: Thirteen healthy participants (16.4. ±. 1.3. years) completed a four-treatment cross-over trial: (1) uninterrupted sitting + high-energy diet; (2) sitting with breaks + high-energy diet; (3) uninterrupted sitting + standard-energy diet; and (4) sitting with breaks + standard-energy diet. For all four conditions, two identical meals were consumed; at 0. h and 3. h. A continuous glucose monitoring system (CGM) recorded interstitial glucose concentrations every five minutes. Linear mixed models examined differences in glucose positive incremental area under the curve (iAUC) and total AUC between the sitting and diet conditions for the first meal, second meal and entire trial period. Results: Compared to the uninterrupted sitting conditions, the breaks condition elicited a 36.0. mmol/L/h (95%CI 6.6-65.5) and 35.9. mmol/L/h (95%CI 6.6-65.5) lower iAUC response after the first and second meal, respectively, but not for the entire trial period or for total AUC. Compared to the standard-energy diet, the high-energy diet elicited a 55.0. mmol/L/h (95%CI 25.8-84.2) and 75.7. mmol/L/h (95%CI 8.6-142.7) higher iAUC response after the first meal and entire trial, respectively. Similar response to the high-energy diet were observed for total AUC. Conclusions: According to iAUC, interrupting sitting had a significant effect on lowering postprandial glucose for both dietary conditions, however, it was not significant when examining total AUC. Larger studies are needed to confirm these findings. Clinical Trial Registration Number: ACTRN12615001145594.