Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring

Hamilton, Ross; XIA, RUIYANG; Nicholas, Chloe; Churm, Rachel; McCarthy, Olivia; Bracken, Richard

doi:10.1002/ejsc.70092

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Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring

Ross Hamilton, RUIYANG XIA, Chloe Nicholas, Rachel Churm

, Olivia McCarthy, Richard Bracken

European Journal of Sport Science, Volume: 25, Issue: 12, Start page: e70092

Swansea University Authors: Ross Hamilton, RUIYANG XIA, Chloe Nicholas, Rachel Churm , Olivia McCarthy, Richard Bracken

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DOI (Published version): 10.1002/ejsc.70092

Abstract

Nine ultra-endurance athletes completed a randomised, crossover trial involving two 28-day dietary arms during which the athletes consumed a carbohydrate-rich diet (carbohydrate 58 ± 3, protein 15 ± 2 and fat 26 ± 2%) containing low- or high-glycaemic-index (LGI or HGI, respectively) carbohydrates....

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Published in:	European Journal of Sport Science
ISSN:	1746-1391 1536-7290
Published:	Wiley 2025
Online Access:	Check full text
URI:	https://cronfa.swan.ac.uk/Record/cronfa70888

first_indexed	2025-11-13T09:36:31Z
last_indexed	2025-12-16T05:27:41Z
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At the start and end of each dietary arm, participants performed a fasted 3-h submaximal run outdoors before ingesting either a low (GI = 32, isomaltulose [Palatinose]) or high (GI = 100, maltodextrin) glycaemic index drink (0.75 g/kg bm/h over 3.5 h). Participants then completed a treadmill run to exhaustion at 74 ± 1% vVO2peak, with pulmonary gas exchange measured over the first hour. Interstitial glucose [iG] was measured via continuous glucose monitoring (Supersapiens, Atlanta, USA). Data were analysed ANOVA and post hoc t-tests with Bonferroni adjustment as appropriate, with p ≤ 0.05 accepted as significant. Mean 24-h [iG] was similar between diets (LGI:102 ± 5 vs. HGI:100 ± 5 mg/dL). [iG] variability measures, including standard deviation (LGI:17 ± 1 vs. HGI:18 ± 2 mg/dL, p = 0.016) and coefficient of variation (LGI:16 ± 1% vs. HGI:18 ± 1%, p = 0.0003), were lower in the LGI diet, with a reduced percentage of time spent below the recommended range (LGI 2 ± 1% vs. HGI 4 ± 2%, p = 0.006. Level 1 [55–69 mg/dL] LGI 1 ± 1% vs. HGI 3 ± 2, p = 0.005). Carbohydrate oxidation during the first hour of the run test was reduced in the LGI diet arm (ΔLGI −0.14 ± 0.32 vs. ΔHGI 0.06 ± 0.28 g·min−1, p = 0.016) but endurance capacity was similar across diets. 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spelling	2025-12-15T15:31:41.8758942 v2 70888 2025-11-13 Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring debecc46f91c2f3b4ca8c69777e53553 Ross Hamilton Ross Hamilton true false 10c03e33d17d666b42b606719bbec832 RUIYANG XIA RUIYANG XIA true false abf60d99b0f99b319d78dc0d6ca8ccdc Chloe Nicholas Chloe Nicholas true false c6cd8267ff0b13f2ea333bbfefdae144 0000-0001-9855-6282 Rachel Churm Rachel Churm true false 4fea3e19b39712dea1d051d317614572 Olivia McCarthy Olivia McCarthy true false f5da81cd18adfdedb2ccb845bddc12f7 0000-0002-6986-6449 Richard Bracken Richard Bracken true false 2025-11-13 Nine ultra-endurance athletes completed a randomised, crossover trial involving two 28-day dietary arms during which the athletes consumed a carbohydrate-rich diet (carbohydrate 58 ± 3, protein 15 ± 2 and fat 26 ± 2%) containing low- or high-glycaemic-index (LGI or HGI, respectively) carbohydrates. At the start and end of each dietary arm, participants performed a fasted 3-h submaximal run outdoors before ingesting either a low (GI = 32, isomaltulose [Palatinose]) or high (GI = 100, maltodextrin) glycaemic index drink (0.75 g/kg bm/h over 3.5 h). Participants then completed a treadmill run to exhaustion at 74 ± 1% vVO2peak, with pulmonary gas exchange measured over the first hour. Interstitial glucose [iG] was measured via continuous glucose monitoring (Supersapiens, Atlanta, USA). Data were analysed ANOVA and post hoc t-tests with Bonferroni adjustment as appropriate, with p ≤ 0.05 accepted as significant. Mean 24-h [iG] was similar between diets (LGI:102 ± 5 vs. HGI:100 ± 5 mg/dL). [iG] variability measures, including standard deviation (LGI:17 ± 1 vs. HGI:18 ± 2 mg/dL, p = 0.016) and coefficient of variation (LGI:16 ± 1% vs. HGI:18 ± 1%, p = 0.0003), were lower in the LGI diet, with a reduced percentage of time spent below the recommended range (LGI 2 ± 1% vs. HGI 4 ± 2%, p = 0.006. Level 1 [55–69 mg/dL] LGI 1 ± 1% vs. HGI 3 ± 2, p = 0.005). Carbohydrate oxidation during the first hour of the run test was reduced in the LGI diet arm (ΔLGI −0.14 ± 0.32 vs. ΔHGI 0.06 ± 0.28 g·min−1, p = 0.016) but endurance capacity was similar across diets. Adopting a 28-day LGI carbohydrate-rich diet and incorporating isomaltulose improved glycaemic variability and reduced time spent below the target glycaemic range with evidence of similar endurance performance capability when compared to a HGI carbohydrate-rich diet. Journal Article European Journal of Sport Science 25 12 e70092 Wiley 1746-1391 1536-7290 endurance, metabolism, nutrition, performance, physiology 1 12 2025 2025-12-01 10.1002/ejsc.70092 COLLEGE NANME COLLEGE CODE Swansea University SU Library paid the OA fee (TA Institutional Deal) This study was funded by BENEO as part of a PhD project co-funded by Supersapiens Inc., the Team Novo Nordisk Foundation, and Swansea University. 2025-12-15T15:31:41.8758942 2025-11-13T09:33:36.6752171 Faculty of Science and Engineering School of Engineering and Applied Sciences - Sport and Exercise Sciences Ross Hamilton 1 RUIYANG XIA 2 Chloe Nicholas 3 Rachel Churm 0000-0001-9855-6282 4 Olivia McCarthy 5 Richard Bracken 0000-0002-6986-6449 6 70888__35827__e77134539f7047f3923ca1042ebc9253.pdf 70888.VOR.pdf 2025-12-15T15:22:39.2282168 Output 1360942 application/pdf Version of Record true © 2025 The Author(s). European Journal of Sport Science published by Wiley-VCH GmbH on behalf of European College of Sport Science. This is an open access article under the terms of the Creative Commons Attribution License. true eng http://creativecommons.org/licenses/by/4.0/
title	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring
spellingShingle	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring Ross Hamilton RUIYANG XIA Chloe Nicholas Rachel Churm Olivia McCarthy Richard Bracken
title_short	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring
title_full	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring
title_fullStr	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring
title_full_unstemmed	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring
title_sort	Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring
author_id_str_mv	debecc46f91c2f3b4ca8c69777e53553 10c03e33d17d666b42b606719bbec832 abf60d99b0f99b319d78dc0d6ca8ccdc c6cd8267ff0b13f2ea333bbfefdae144 4fea3e19b39712dea1d051d317614572 f5da81cd18adfdedb2ccb845bddc12f7
author_id_fullname_str_mv	debecc46f91c2f3b4ca8c69777e53553_*_Ross Hamilton 10c03e33d17d666b42b606719bbec832__RUIYANG XIA abf60d99b0f99b319d78dc0d6ca8ccdc__Chloe Nicholas c6cd8267ff0b13f2ea333bbfefdae144__Rachel Churm 4fea3e19b39712dea1d051d317614572__Olivia McCarthy f5da81cd18adfdedb2ccb845bddc12f7_*_Richard Bracken
author	Ross Hamilton RUIYANG XIA Chloe Nicholas Rachel Churm Olivia McCarthy Richard Bracken
author2	Ross Hamilton RUIYANG XIA Chloe Nicholas Rachel Churm Olivia McCarthy Richard Bracken
format	Journal article
container_title	European Journal of Sport Science
container_volume	25
container_issue	12
container_start_page	e70092
publishDate	2025
institution	Swansea University
issn	1746-1391 1536-7290
doi_str_mv	10.1002/ejsc.70092
publisher	Wiley
college_str	Faculty of Science and Engineering
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hierarchy_top_title	Faculty of Science and Engineering
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hierarchy_parent_title	Faculty of Science and Engineering
department_str	School of Engineering and Applied Sciences - Sport and Exercise Sciences{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Sport and Exercise Sciences
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description	Nine ultra-endurance athletes completed a randomised, crossover trial involving two 28-day dietary arms during which the athletes consumed a carbohydrate-rich diet (carbohydrate 58 ± 3, protein 15 ± 2 and fat 26 ± 2%) containing low- or high-glycaemic-index (LGI or HGI, respectively) carbohydrates. At the start and end of each dietary arm, participants performed a fasted 3-h submaximal run outdoors before ingesting either a low (GI = 32, isomaltulose [Palatinose]) or high (GI = 100, maltodextrin) glycaemic index drink (0.75 g/kg bm/h over 3.5 h). Participants then completed a treadmill run to exhaustion at 74 ± 1% vVO2peak, with pulmonary gas exchange measured over the first hour. Interstitial glucose [iG] was measured via continuous glucose monitoring (Supersapiens, Atlanta, USA). Data were analysed ANOVA and post hoc t-tests with Bonferroni adjustment as appropriate, with p ≤ 0.05 accepted as significant. Mean 24-h [iG] was similar between diets (LGI:102 ± 5 vs. HGI:100 ± 5 mg/dL). [iG] variability measures, including standard deviation (LGI:17 ± 1 vs. HGI:18 ± 2 mg/dL, p = 0.016) and coefficient of variation (LGI:16 ± 1% vs. HGI:18 ± 1%, p = 0.0003), were lower in the LGI diet, with a reduced percentage of time spent below the recommended range (LGI 2 ± 1% vs. HGI 4 ± 2%, p = 0.006. Level 1 [55–69 mg/dL] LGI 1 ± 1% vs. HGI 3 ± 2, p = 0.005). Carbohydrate oxidation during the first hour of the run test was reduced in the LGI diet arm (ΔLGI −0.14 ± 0.32 vs. ΔHGI 0.06 ± 0.28 g·min−1, p = 0.016) but endurance capacity was similar across diets. Adopting a 28-day LGI carbohydrate-rich diet and incorporating isomaltulose improved glycaemic variability and reduced time spent below the target glycaemic range with evidence of similar endurance performance capability when compared to a HGI carbohydrate-rich diet.
published_date	2025-12-01T05:34:01Z
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Glycaemic Impact of Low‐ and High‐Glycaemic Index Carbohydrate Diets in Ultra‐Endurance Athletes: Insights From Continuous Glucose Monitoring

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