Pre-Exercise Breakfast Ingestion versus Extended Overnight Fasting Increases Postprandial Glucose Flux after Exercise in Healthy Men: Pre-exercise feeding and postprandial glucose flux

Robert M Edinburgh, Aaron Hengist, Harry A Smith, Rebecca L Travers, Francoise Koumanov, James A Betts, Dylan Thompson, Jean-Philippe Walhin, Gareth A Wallis, D Lee Hamilton, Emma J Stevenson, Kevin D Tipton, Javier T Gonzalez

Research output: Contribution to journalArticle

16 Citations (Scopus)
12 Downloads (Pure)


The aim of this study was to characterize postprandial glucose flux after exercise in the fed versus overnight fasted state and to investigate the potential underlying mechanisms. In a randomized order, twelve men underwent breakfast-rest [(BR) 3 h semirecumbent], breakfast-exercise [(BE) 2 h semirecumbent 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 after exercise (after rest on BR). Dual stable isotope tracers ([U- 13C] glucose ingestion and [6,6- 2H 2] 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. Breakfast before exercise increased postexercise plasma glucose disposal rates during the OGTT, from 44 g/120 min in FE {35 to 53 g/120 min [mean (normalized 95% confidence interval)] to 73 g/120 min in BE [55 to 90 g/120 min; 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 (196 to 332 pg/ml) lower in BE versus FE (P = 0.01). Breakfast before exercise increases postexercise 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.

Original languageEnglish
Article number00163
Pages (from-to)E1062-E1074
Number of pages13
JournalAmerican Journal of Physiology: Endocrinology and Metabolism
Issue number5
Early online date14 Aug 2018
Publication statusPublished - 1 Nov 2018



  • Breakfast
  • Exercise
  • Glycemia
  • Insulin sensitivity
  • Metabolism

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

Cite this