Substrate utilization during brisk walking is affected by glycemic index and fructose content of a pre-exercise meal

Abstract

The purpose of the present study was to investigate whether both glycemic index (GI) and fructose content of a pre-exercise meal would affect substrate utilization during subsequent brisk walking. Ten healthy young males completed 60 min of 46% [Formula: see text] brisk walking 2 h after they consumed one of three breakfasts: a low-GI meal without fructose (LGI), a low-GI meal including fructose (LGIF), and a high-GI meal without fructose (HGI). The calculated GI values for the three meals were 41, 39, and 72, respectively. Substrate utilization was measured using indirect respiratory calorimetry method. During the postprandial period, the incremental area under the blood response curve values of glucose and insulin were higher in the HGI trial, compared with those in the LGI and LGIF trials (HGI vs. LGI and LGIF: Glucose 223.6 ± 19.1 vs. 70.2 ± 7.4 and 114.1 ± 16.4 mmol min L(-1); Insulin 4257 ± 932 vs. 920 ± 319 and 1487 ± 348 mU min L(-1)). During exercise, substrate preference was distinct based on different pre-exercise carbohydrate meals. Higher fat and lower carbohydrate oxidation was observed in the LGI trial, whereas both the HGI and LGIF trials were characterized by higher carbohydrate and lower fat oxidation (LGI vs. LGIF and HGI: Carbohydrate 59.3 ± 2.4 vs. 69.8 ± 3.9 and 72.7 ± 3.9 g; Fat 22.7 ± 2.0 vs. 18.5 ± 1.7 and 17.6 ± 1.3 g; P < 0.05). In conclusion, the presence of fructose in a LGI breakfast resulted in similar substrate utilization during subsequent brisk walking with that induced by a HGI breakfast. It appears that both the GI and fructose content in a breakfast individually affect substrate utilization during subsequent moderate intensity exercise.

Metabolic response to different glycemic indexes of pre-exercise meal

“…In the present study, regardless of dietary intake of HGI or LGI or fasting state with hydration with H 2 O or CHO-electrolyte drink, no difference was observed in CHO and fat oxidation during exercise, which is consistent with result of the study by Moore et al 17 , who compared HGI and LGI, and with results obtained by Chen et al 18 and Wong et al 19 , who assessed pre-exercise meals with different GI but with hydration during exercise with CHO-electrolyte drink. The current results can be justified by the presence of fructose in the LGI meal composition, since the metabolism of fructose in the liver occurs from the second glycolysis reaction, being readily oxidized 20 and thus showing a behavior similar to HGI meal, as evidenced by the study of Sun et al 21 .…”

Is There a Specific Role for Sucrose in Sports and Exercise Performance?

“…Sucrose being a moderate GI carbohydrate may therefore provide a useful source of carbohydrate as part of a lower GI meal, as compared with higher GI carbohydrates such as glucose. However, inclusion of free fructose within a low GI meal has been observed to result in a paradoxical increase in carbohydrate oxidation and reduction in fat oxidation to the extent that substrate utilization, at least during low-intensity exercise, is similar to that seen following a high GI meal (Sun et al, 2012). Therefore, the effect of inclusion of sucrose within a low GI meal, as compared with a low GI meal without sucrose, needs to be evaluated with respect to the potential to maintain a sustained release of energy (relative to high GI meal ingestion) in exercise situations where additional carbohydrate provision is not readily available.…”

Effects of carbohydrate and protein co-ingestion during short-term moderate-intensity exercise on cognitive function

“…Capillary blood samples were collected to determine the blood lactate and glucose concentrations using YSI 1500 (Yellow Spring Instrument Co. Ltd., USA) and a biochemical analyzer (Roche1 ACCU-CHEK Reflotron plus, USA), respectively. Similar to previous study [31], subjective measures, such as RPE, perceived thirst (PT), and abdominal discomfort (AD) were recorded. The PT and AD varied from 0 to 10, where 0 denoted "not so much" and 10 denoted "very much".…”

“…Heart rate was assessed with a Polar heart rate monitor (PolarTeam System, Polar Electroy, Finland), and rating of perceived exertion (RPE) was measured using the 6-20 Borg scale [30]. The test was considered maximal when at least two of the following criteria were met: heart rate fail to increase with an increase in exercise intensity, a plateau in oxygen uptake with increasing workload, a respiratory exchange ratio of greater than 1.15, and an RPE greater than 17 [31]. On the basis of the preliminary test results, a running speed equivalent to 70% of each participant's VO2peak was determined.…”