Effects of ordered eating on blood glucose, substrate utilization, and perceptual responses with a steady-state exercise bout

Abstract

Objectives: The sequence of a meal's macronutrient consumption influences postprandial blood glucose, but it is unknown whether altering the order of macronutrient consumption before exercise affects glycemic and metabolic responses during exercise.

Design: Randomized controlled crossover trial.

Methods: Physically active adults who self-reported being free of cardiometabolic disease (n = 18; 8 male, 10 female) fasted for ≥8 h and were randomized to a rice-first or rice-last condition for one visit and the opposite for a second visit. Participants were asked to consume 150 g broccoli and 100 g chicken combined and 150 g rice separately. Post-meal, participants rested for 60 min before a 30-min run at 70 % of maximum heart rate. Blood glucose and respiratory exchange were measured regularly during rest and exercise.

Results: There was a condition × time interaction for blood glucose (p < .001), with higher levels for rice-first than rice-last 30 min post-eating (133 ± 20 vs. 106 ± 21; p < .001). Rice-first led to a larger reduction in blood glucose than rice-last from pre- to post-exercise (21.4 ± 22.1 vs. 4.6 ± 23.5 mg/dL; p = .035). There was a condition × time interaction for respiratory exchange ratio at rest (p < .001), with 5-6 % higher values with rice-first than rice-last from 40 to 55 min postprandial. During exercise, respiratory exchange ratio was approximately 2.5 % higher with rice-first than rice-last (p = .029).

Conclusions: A rice-first meal pattern elicited a higher postprandial blood glucose shortly after eating and a larger blood glucose drop during exercise. Further, it led to a greater rise in resting respiratory exchange ratio, which was maintained during exercise.

Keywords: Carbohydrates; Diet; Exercise; Glucose; Meals; Nutrition.