Substituting carbohydrate at lunch for added protein increases fat oxidation during subsequent exercise in healthy males

Tommy Slater; William J A Mode; Louise C Bonnard; Cian Sweeney; Mark P Funnell; Harry A Smith; John Hough; Ruth M James; Ian Varley; Craig Sale; James A Betts; Lewis J James; David J Clayton

doi:10.1210/clinem/dgae237

Substituting carbohydrate at lunch for added protein increases fat oxidation during subsequent exercise in healthy males

J Clin Endocrinol Metab. 2024 Apr 13:dgae237. doi: 10.1210/clinem/dgae237. Online ahead of print.

Authors

Affiliations

¹ Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK.
² National Centre for Sport and Exercise Medicine, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK.
³ Centre for Nutrition Exercise and Metabolism, Department for Health, University of Bath, Bath, BA2 7AY, UK.
⁴ Department of Sport and Exercise Sciences, Manchester Metropolitan University Institute of Sport, Manchester, M1 7EL, UK.

PMID: 38609167
DOI: 10.1210/clinem/dgae237

Abstract

Context: How pre-exercise meal composition influences metabolic and health responses to exercise later in the day is currently unclear.

Objective: Examine the effects of substituting carbohydrate for protein at lunch on subsequent exercise metabolism, appetite, and energy intake.

Methods: Twelve healthy males completed three trials in randomized, counterbalanced order. Following a standardized breakfast (779 ± 66 kcal; ∼08:15), participants consumed a lunch (1186 ± 140 kcal; ∼13:15) containing either 0.2 g·kg-1 carbohydrate and ∼2 g·kg-1 protein (LO-CARB), 2 g·kg-1 carbohydrate and ∼0.4 g·kg-1 protein (HI-CARB), or fasted (FAST). Participants later cycled at ∼60% V̇O2peak for 1 h (∼16:15) and post-exercise ad-libitum energy intake was measured (∼18:30). Substrate oxidation, subjective appetite, and plasma concentrations of glucose, insulin, non-esterified fatty acids (NEFA), peptide YY (PYY), glucagon-like peptide-1 (GLP-1), and acylated ghrelin (AG) were measured for 5 h post-lunch.

Results: Fat oxidation was greater during FAST (+11.66 ± 6.63 g) and LO-CARB (+8.00 ± 3.83 g) than HI-CARB (p < 0.001), with FAST greater than LO-CARB (+3.67 ± 5.07 g; p < 0.05). NEFA were lowest in HI-CARB and highest in FAST, with insulin demonstrating the inverse response (all p < 0.01). PYY and GLP-1 demonstrated a stepwise pattern, with LO-CARB greatest and FAST lowest (all p < 0.01). AG was lower during HI-CARB and LO-CARB versus FAST (p < 0.01). Energy intake in LO-CARB was lower than FAST (-383 ± 233 kcal; p < 0.001) and HI-CARB (-313 ± 284 kcal; p < 0.001).

Conclusion: Substituting carbohydrate for protein in a pre-exercise lunch increased fat oxidation, suppressed subjective and hormonal appetite, and reduced post-exercise energy intake.

Keywords: Carbohydrate restriction; appetite hormones; energy intake; exercise metabolism; fasting; protein.