Metabolic responses to high glycemic index and low glycemic index meals: a controlled crossover clinical trial

Abstract

BackgroundThe consumption of low glycemic index (LGI) foods before exercise results in slower and more stable glycemic increases. Besides maintaining an adequate supply of energy during exercise, this response may favor an increase in fat oxidation in the postprandial period before the exercise compared to high glycemic index (HGI) foods. The majority of the studies that evaluated the effect of foods differing in glycemic index on substrate oxidation during the postprandial period before the exercise are acute studies in which a single meal is consumed right before the exercise. The purpose of this study was to investigate the effect of consuming two daily HGI or LGI meals for five consecutive days on substrate oxidation before the exercise and in the concentrations of glucose, insulin and free fatty acids before and during a high intensity exercise.MethodsFifteen male cyclists, aged 24.4 ± 3.8 years, with body mass index of 21.9 ± 1.4 kg.m-2 and a VO2 max of 70.0 ± 5.3 mL.kg-1.min-1, participated in this crossover study. All test meals were consumed in the laboratory. On days 1 and 5, substrate oxidation (30 minutes before and 90 minutes after breakfast (HGI or LGI)) and diet-induced thermogenesis (90 minutes postprandial) were assessed before the exercise. The levels of glucose, insulin, and free fatty acids were determined during 2 h after breakfast on these same days. Ninety minutes after breakfast, subjects completed a 30 min cycloergometric exercise at 85 to 95% of their maximum heart rate, during which lactate concentrations were assessed.ResultsThe consumption of HGI meals resulted in higher areas under the glycemic and insulinemic curves in the postprandial period. However, glycemia did not differ by study treatment during exercise. There were no differences in free fatty acids in the postprandial period or in lactate levels during exercise. LGI meals resulted in lower fat oxidation and higher carbohydrate oxidation than the HGI meal in the postprandial period.ConclusionsThe results do not support a differential glycemia according to glycemic index during exercise. The ingestion of LGI foods did not lead to higher fat oxidation relative to the ingestion of HGI foods.Trial registrationACTRN: ACTRN12609000522213

Influence of Glycemic Index-Based Menu on Endurance Performance of Athletes

“…In consuming a high-GI meal before practicing sport, the concentration of blood glucose will rise and lower sharply and attain a higher level at peak times than in consuming low-GI meal with similar number of carbohydrates (Mondazzi et al, 2009). This finding is confirmed by Burke et al (1998) and Cocate et al (2011) suggesting that the rate of glucose oxidation is higher after consuming high-GI meal. The decrease of blood glucose level occurs after 5-km run within high-IG group; this is presumably caused by the insulin level after meal consumption (before training) is still high enough in high-GI group, bringing the glucoses into liver and muscle to be stored as glycogens and reducing the glucose production in liver (Marmy-Cornus et al, 1996).…”

High Dietary ω-6:ω-3 PUFA Ratio Is Positively Associated with Excessive Adiposity and Waist Circumference

“…In this state, lower levels of adiponectin are observed [9] . However, the degree to which an inappropriate intake of macronutrients, and particularly a high dietary ω-6:ω-3 PUFA ratio, may be associated with adiposity and abnormal adiponectin levels remains unclear [10] .…”

Comparison between Preexercise Meals Intake Effect with Different Glycemic Load on Exercise Performance in Female Athletes

“…Similar results obtained from several studies which evaluated the effects of consuming foods with different GI before exercise on RPE values [9,19,27]. Stevenson et al examined the effects of three hr pre-exercise mixed breakfast intake with HGI or LGI content (78 or 44) on substrate utilization of healthy active women, during a 60 minutes run at 65% VO2max.No significant difference observed between high or low GI meals in rating of percieved exertion [9].…”