Whey protein consumption following fasted exercise reduces early postprandial glycaemia in centrally obese males: a randomised controlled trial

Abstract

Purpose: Acute submaximal exercise and whey protein supplementation have been reported to improve postprandial metabolic and appetite responses to a subsequent meal independently. We aimed to examine the combination of these strategies on postprandial responses to a carbohydrate-rich breakfast.

Methods: Twelve centrally obese males (age 41 ± 3 years, waist circumference 123.4 ± 2.9 cm), completed three trials in a single-blind, crossover design. Participants rested for 30 min (CON) or completed 30 min low-moderate-intensity treadmill walking (51 ± 1% [Formula: see text]) followed immediately by ingestion of 20 g whey protein (EX + PRO) or placebo (EX). After 15 min, a standardised breakfast was consumed and blood, expired gas and subjective appetite were sampled postprandially. After 240 min, an ad libitum lunch meal was provided to assess energy intake.

Results: During EX + PRO, post-breakfast peak blood glucose was reduced when compared with EX and CON (EX + PRO: 7.6 ± 0.4 vs EX: 8.4 ± 0.3; CON: 8.3 ± 0.3 mmol l^-1, p ≤ 0.04). Early postprandial glucose AUC_{0-60 min} was significantly lower under EX + PRO than EX (p = 0.011), but not CON (p = 0.12). Over the full postprandial period, AUC_{0-240 min} during EX + PRO did not differ from other trials (p > 0.05). Peak plasma insulin concentrations and AUC_{0-240 min} were higher during EX + PRO than CON, but similar to EX. Plasma triglyceride concentrations, substrate oxidation and subjective appetite responses were similar across trials and ad libitum energy intake was not influenced by prior fasted exercise, nor its combination with whey protein supplementation (p > 0.05).

Conclusion: Following fasted low-moderate-intensity exercise, consuming whey protein before breakfast may improve postprandial glucose excursions, without influencing appetite or subsequent energy intake, in centrally obese males.

Trial registration number: NCT02714309.

Keywords: Exercise; Glycaemia; Insulin; Postprandial; Whey protein.

Fig. 1

Schematic representation of experimental trials. WP whey protein, BL baseline

Fig. 2

Mean ± SEM (n = 12) temporal changes in blood glucose (a) and plasma insulin (c) concentrations, with associated AUC for glucose (b) and insulin (d). Significant differences (p < 0.05) between conditions at individual time points are defined as follows; a EX + PRO vs CON; b EX vs CON; c EX + PRO vs EX. Significant differences between bars are denoted with an asterisk. Dotted line indicates time of breakfast consumption. EX + PRO exercise with whey protein preload trial, EX exercise trial, CON resting trial

Fig. 3

Mean ± SEM (n = 12) temporal changes in plasma triglyceride (a) and glycerol (c) concentrations with associated AUC for triglyceride (b) and glycerol (d). Significant differences (p < 0.05) between conditions at individual time points are defined as follows; a EX + PRO vs CON; b EX vs CON; c EX + PRO vs EX. Significant differences between bars are denoted with an asterisk. Dotted line indicates time of breakfast consumption. EX + PRO exercise with whey protein preload trial, EX exercise trial, CON resting trial

Fig. 4

Mean ± SEM (n = 12) temporal changes (a) and AUC (b) for combined appetite score. Dotted lines indicate time of meal consumption. EX + PRO exercise with whey protein preload trial, EX exercise trial, CON resting trial