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Pre-Exercise Breakfast Ingestion versus Extended Overnight Fasting Increases Postprandial Glucose Flux after Exercise in Healthy Men

Lookup NU author(s): Professor Emma Stevenson

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by American Physiological Society, 2018.

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Abstract

AIMS:To characterize postprandial glucose flux after exercise in the fed versus overnight fasted-state and to investigate potential underlying mechanisms.METHODS:In a randomized order, twelve men underwent breakfast-rest (BR; 3 h semi-recumbent), breakfast-exercise (BE; 2 h semi-recumbent before 60-min of cycling (50% peak power output) and overnight fasted-exercise (FE; as per BE omitting breakfast) trials. An oral glucose tolerance test (OGTT) was completed post-exercise (post-rest on BR). Dual stable isotope tracers ([U-¹³C] glucose ingestion and [6,6-²H₂] glucose infusion) and muscle biopsies were combined to assess postprandial plasma glucose kinetics and intramuscular signaling, respectively. Plasma intestinal fatty acid binding (I-FABP) concentrations were determined as a marker of intestinal damage.RESULTS:Breakfast before exercise increased post-exercise plasma glucose disposal rates during the OGTT, from 44 g•120 min^-1 in FE [35 to 53 g•120 min^-1] (mean [normalized 95% CI]) to 73 g•120 min^-1 in BE [55 to 90 g•120 min^-1; p = 0.01]. This higher plasma glucose disposal rate was, however, offset by increased plasma glucose appearance rates (principally OGTT-derived), resulting in a glycemic response that did not differ between BE and FE (p = 0.11). Plasma I-FABP concentrations during exercise were 264 pg•mL^-1 [196 to 332 pg•mL^-1] lower in BE versus FE (p = 0.01).CONCLUSION:Breakfast before exercise increases post-exercise postprandial plasma glucose disposal, which is offset (primarily) by increased appearance rates of orally-ingested glucose. Therefore, metabolic responses to fed-state exercise cannot be readily inferred from studies conducted in a fasted state.

Publication metadata

Author(s): Edinburgh RM, Hengist A, Smith HA, Travers RL, Koumanov F, Betts JA, Thompson D, Walhin JP, Wallis GA, Hamilton DL, Stevenson EJ, Tipton KD, Gonzalez JT

Publication type: Article

Publication status: Published

Journal: American Journal of Physiology Endocrinology and Metabolism

Year: 2018

Volume: 315

Issue: 5

Pages: E1062–E1074

Print publication date: 01/11/2018

Online publication date: 09/11/2018

Acceptance date: 02/08/2018

Date deposited: 02/10/2018

ISSN (print): 0193-1849

ISSN (electronic): 1522-1555

Publisher: American Physiological Society

URL: https://doi.org/10.1152/ajpendo.00163.2018

DOI: 10.1152/ajpendo.00163.2018

PubMed id: 30106621

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