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Low-glycemic index meal after exercise improves next-day lipids
Adults who were assigned to complete 90 minutes of brisk exercise and then fast or consume a low-glycemic index meal saw an improved postprandial lipid response after a high-fat breakfast the next day vs. those who consumed a high-glycemic index meal after exercise, study results indicate.
“The most significant finding in this study was that a single evening, 90-minute exercise session of brisk walking, followed by either no caloric replacement or [low-glycemic index] food, resulted in improved baseline combined with postprandial metabolic responses to a high-fat breakfast meal the following day,” Mojtaba Kaviani, MSc, a research and teaching assistant in the college of kinesiology at the University of Saskatchewan in Canada, and colleagues wrote. “Compared with [a high-glycemic index] meal, the [low-glycemic index] meal after the evening exercise session elicited a lower insulin response after a high-fat breakfast the next day.”
Kaviani and colleagues analyzed data from 23 adults with overweight or obesity who were otherwise healthy and not taking medications that could affect blood lipid or glucose levels (16 men; mean age, 31 years; mean BMI, 29.5 kg/m²; mean waist circumference, 97.6 cm). Each participant underwent four 2-day trials in a randomized, counterbalanced order than included an exercise session (90 minutes of brisk walking) without caloric replacement (EX); an exercise session followed by a low-glycemic index meal of boiled lentils, tomato sauce and canola oil (EX-LGI); exercise session followed by a high-glycemic index meal of instant mashed potatoes, egg whites and white bread (EX-HGI); and a control session with no exercise (90 minutes of sitting). After each of the four sessions, participants returned to the laboratory after a 10-hour overnight fast. After providing blood samples and undergoing fat oxidation assessment, participants consumed a high-fat breakfast (fast food breakfast sandwich), selected intentionally to elicit a rise in insulin and triglycerides. Participants provided blood samples at 30 minutes and 1, 2, 4 and 6 hours after the high-fat meal.
Researchers found that mean fat oxidation was higher in the EX group vs. the EX-HGI group (6.9 g·h–1 vs. 6.3 g·h–1; P = .007) and controls (5.9 g·h–1; P = .00002); mean fat oxidation was also higher for the EX-LGI group vs. controls (6.6 g·h–1; P = .002).
Total area under the curve for triglycerides was 18% to 32% lower among participants in the EX and EX-LGI groups vs. controls (P = .0005 and P = .0001, respectively) and vs. participants in the EX-HGI group (P = .05 and P = .021, respectively).
“[Triglyceride] incremental area under the curve followed the same trend; however, the difference between conditions did not reach a level of statistical significance (P = .063),” the researchers wrote. “This indicates that reductions in [triglyceride] levels were largely mediated by reductions in baseline [triglycerides]. – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.