The influence of high-carbohydrate meals with different glycaemic indices on substrate utilisation during subsequent exercise

Abstract

The present study was designed to examine the effects of mixed high-carbohydrate meals with different glycaemic indices (GI) on substrate utilization during subsequent exercise. Nine healthy male recreational runners (age 26·8 (SEM 1·1) years, body mass 74·7 (SEM 2·4) kg, V O 2 max 58·1 (SEM 1·7) ml/kg per min) completed three trials: high-glycaemic-index meal (HGI), low-glycaemic-index meal (LGI) and fasting (FAST), separated by 7 d. The test meals contained 2 g carbohydrate/kg body mass, they were isoenergetic and the GI values were 77·4, 36·9 and 0·0 respectively. In each trial, subjects consumed the test meal 3 h before performing a 60 min run at 65 % V O 2 max on a motorized treadmill. Ingestion of the HGI and LGI resulted in hyperglycaemia and hyperinsulinaemia during the postprandial period compared with the FAST (P, 0·05). The incremental area under the curve for plasma glucose was 2-fold higher for HGI compared with LGI (108·7 v. 48·9 mmol/l per min). In contrast, plasma non-esterified fatty acid concentrations were significantly lower following HGI and LGI compared with FAST (P, 0·05). During the subsequent submaximal exercise, plasma glucose declined to below the fasting value in HGI compared with LGI and FAST (P, 0·05). The estimated total fat oxidation was significantly higher for the LGI than the HGI during exercise (P,0·05). In summary, both pre-exercise carbohydrate meals resulted in lower rates of fat oxidation during subsequent exercise than when subjects performed exercise in the fasting state. However, the LGI resulted in a higher rate of fat oxidation during exercise than following the consumption of the HGI.

Influence of the glycaemic index of an evening meal on substrate oxidation following breakfast and during exercise the next day in healthy women

“…This is in agreement with previous studies that have investigated the effect of a single pre-exercise meal or food with differing GI values on substrate metabolism during exercise (Wee et al, 1999;Wu et al, 2003;. It has been suggested that the chronic intake of a LGI diet results in changes in fuel partitioning and substrate oxidation due to reduced insulinaemia in the postprandial period.…”

“…Reduced hyperinsulinaemia during the postprandial period following the LGI meal reduces the suppression of fat oxidation compared to when a HGI meal is consumed. This allows a shift in substrate utilization toward fat oxidation during the subsequent exercise as well as providing a sustainable source of CHO (Wu et al, 2003). The results of Figure 5 Blood lactate concentrations (mmol l À1 ) during the HGI and LGI trials (mean7s.e.m.).…”

“…Similarly, no differences in FFA, glycerol or lactate concentrations were reported between the trials. Several studies have reported higher rates of fat oxidation during exercise when a LGI pre-exercise meal or food is consumed (Thomas et al, 1991;Wee et al, 1999;Wu et al, 2003;Stevenson et al, 2006). Reduced hyperinsulinaemia during the postprandial period following the LGI meal reduces the suppression of fat oxidation compared to when a HGI meal is consumed.…”

“…This is despite the fact that the breakfast was exactly the same in both trials. Several studies have reported that the consumption of LGI foods reduces hunger and/or promotes satiety relative to consumption of HGI foods in the hours following consumption of the meal (Ludwig et al, 1999;Ball et al, 2003;Warren et al, 2003;Wu et al, 2003). The effect of glycaemic CHO on food intake appears to be related to their effects on blood glucose (Anderson and Woodend, 2003).…”

Effect of breakfast glycemic index on metabolic responses during rest and exercise in overweight and non-overweight adolescent girls

“…Substituting a HGI breakfast for a LGI breakfast may, therefore, be particularly beneficial for OW individuals through increased glycemic control (Willett et al, 2002), fat oxidation (Stevenson et al, 2009) and satiety (Ludwig et al, 1999). However, the majority of studies investigating the impact of GI on fat oxidation have included endurance trained or recreationally active adults as participants (Wu et al, 2003;Stevenson et al, 2006) and we are unaware of similar studies including OW individuals or young people, despite well-recognised differences in metabolism between adolescents and adults (Riddell et al, 2008). Therefore, we examined the effect of mixed breakfast meals providing HGI or LGI carbohydrates on metabolic responses and substrate utilisation during rest and exercise in OW and non-overweight (NO) adolescent girls.…”