PMID- 32697366 OWN - NLM STAT- MEDLINE DCOM- 20210412 LR - 20210412 IS - 1469-7793 (Electronic) IS - 0022-3751 (Print) IS - 0022-3751 (Linking) VI - 599 IP - 3 DP - 2021 Feb TI - Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability. PG - 771-790 LID - 10.1113/JP280221 [doi] AB - KEY POINTS: Brief (5-6 days) adaptation to a low carbohydrate high fat diet in elite athletes increased exercise fat oxidation to rates previously observed with medium (3-4 weeks) or chronic (>12 months) adherence to this diet, with metabolic changes being washed out in a similar time frame. Increased fat utilisation during exercise was associated with a 5-8% increase in oxygen cost at speeds related to Olympic Programme races. Acute restoration of endogenous carbohydrate (CHO) availability (24 h high CHO diet, pre-race CHO) only partially restored substrate utilisation during a race warm-up. Fat oxidation continued to be elevated above baseline values although it was lower than achieved by 5-6 days' keto adaptation; CHO oxidation only reached 61% and 78% of values previously seen at exercise intensities related to race events. Acute restoration of CHO availability failed to overturn the impairment of high-intensity endurance performance previously associated with low carbohydrate high fat adaptation, potentially due to the blunted capacity for CHO oxidation. ABSTRACT: We investigated substrate utilisation during exercise after brief (5-6 days) adaptation to a ketogenic low-carbohydrate (CHO), high-fat (LCHF) diet and similar washout period. Thirteen world-class male race walkers completed economy testing, 25 km training and a 10,000 m race (Baseline), with high CHO availability (HCHO), repeating this (Adaptation) after 5-6 days' LCHF (n = 7; CHO: <50 g day(-1) , protein: 2.2 g kg(-1) day(-1) ; 80% fat) or HCHO (n = 6; CHO: 9.7 g kg(-1) day(-1) ; protein: 2.2 g kg(-1) day(-1) ) diet. An Adaptation race was undertaken after 24 h HCHO and pre-race CHO (2 g kg(-1) ) diet, identical to the Baseline race. Substantial (>200%) increases in exercise fat oxidation occurred in the LCHF Adaptation economy and 25 km tests, reaching mean rates of approximately 1.43 g min(-1) . However, relative V̇O2 (ml min(-1) kg(-1) ) was higher (P < 0.0001), by approximately 8% and 5% at speeds related to 50 km and 20 km events. During Adaptation race warm-up in the LCHF group, rates of fat and CHO oxidation at these speeds were decreased and increased, respectively (P < 0.001), compared with the previous day, but were not restored to Baseline values. Performance changes differed between groups (P = 0.009), with all HCHO athletes improving in the Adaptation race (5.7 (5.6)%), while 6/7 LCHF athletes were slower (2.2 (3.4)%). Substrate utilisation returned to Baseline values after 5-6 days of HCHO diet. In summary, robust changes in exercise substrate use occurred in 5-6 days of extreme changes in CHO intake. However, adaptation to a LCHF diet plus acute restoration of endogenous CHO availability failed to restore high-intensity endurance performance, with CHO oxidation rates remaining blunted. CI - (c) 2020 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society. FAU - Burke, Louise M AU - Burke LM AUID- ORCID: 0000-0001-8866-5637 AD - Exercise and Nutrition Research Program, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. AD - Australian Institute of Sport, Canberra, Australia. FAU - Whitfield, Jamie AU - Whitfield J AUID- ORCID: 0000-0002-8961-8872 AD - Exercise and Nutrition Research Program, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. FAU - Heikura, Ida A AU - Heikura IA AUID- ORCID: 0000-0002-1088-428X AD - Exercise and Nutrition Research Program, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. AD - Australian Institute of Sport, Canberra, Australia. FAU - Ross, Megan L R AU - Ross MLR AD - Exercise and Nutrition Research Program, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. AD - Australian Institute of Sport, Canberra, Australia. FAU - Tee, Nicolin AU - Tee N AUID- ORCID: 0000-0003-1130-9516 AD - Australian Institute of Sport, Canberra, Australia. FAU - Forbes, Sara F AU - Forbes SF AUID- ORCID: 0000-0001-6726-9328 AD - Australian Institute of Sport, Canberra, Australia. FAU - Hall, Rebecca AU - Hall R AUID- ORCID: 0000-0001-7489-1668 AD - Exercise and Nutrition Research Program, Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. AD - Australian Institute of Sport, Canberra, Australia. FAU - McKay, Alannah K A AU - McKay AKA AD - Australian Institute of Sport, Canberra, Australia. AD - School of Human Sciences (Exercise and Sport Science), University of Western Australia, Crawley, Australia. AD - Western Australian Institute of Sport, Mt, Claremont, Western Australia, Australia. FAU - Wallett, Alice M AU - Wallett AM AUID- ORCID: 0000-0002-7320-3875 AD - Australian Institute of Sport, Canberra, Australia. AD - University of Canberra Research Institute for Sport and Exercise, Canberra, Australia. FAU - Sharma, Avish P AU - Sharma AP AD - Australian Institute of Sport, Canberra, Australia. AD - Griffith Sports Physiology and Performance, School of Allied Health Sciences, Griffith University, Southport, Australia. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20200819 PL - England TA - J Physiol JT - The Journal of physiology JID - 0266262 RN - 0 (Dietary Carbohydrates) RN - 9005-79-2 (Glycogen) SB - IM CIN - J Physiol. 2021 Feb;599(3):727-728. PMID: 32776510 CIN - J Physiol. 2021 Feb;599(3):731-732. PMID: 33034381 MH - Adaptation, Physiological MH - Diet, Carbohydrate-Restricted MH - *Diet, High-Fat MH - Dietary Carbohydrates MH - *Glycogen MH - Humans MH - Male MH - Physical Endurance PMC - PMC7891450 OTO - NOTNLM OT - athletic performance OT - ketogenic diet OT - sports nutrition EDAT- 2020/07/23 06:00 MHDA- 2021/04/13 06:00 PMCR- 2020/08/19 CRDT- 2020/07/23 06:00 PHST- 2020/05/22 00:00 [received] PHST- 2020/07/14 00:00 [accepted] PHST- 2020/07/23 06:00 [pubmed] PHST- 2021/04/13 06:00 [medline] PHST- 2020/07/23 06:00 [entrez] PHST- 2020/08/19 00:00 [pmc-release] AID - TJP14268 [pii] AID - 10.1113/JP280221 [doi] PST - ppublish SO - J Physiol. 2021 Feb;599(3):771-790. doi: 10.1113/JP280221. Epub 2020 Aug 19.