1. Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability
- Author
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Nicolin Tee, Sara F. Forbes, Rebecca Hall, Jamie Whitfield, Avish P. Sharma, Ida A. Heikura, Alice Wallett, Louise M. Burke, Megan L. Ross, Alannah K A McKay, Burke, Louise M, Whitfield, Jamie, Heikura, Ida A, Ross, Megan LR, Tee, Nicolin, Forbes, Sara F, Hall, Rebecca, McKay, Alannah KA, Wallett, Alice M, and Sharma, Avish P
- Subjects
0301 basic medicine ,Male ,Physiology ,medicine.medical_treatment ,Sports nutrition ,Diet, High-Fat ,03 medical and health sciences ,chemistry.chemical_compound ,Diet, Carbohydrate-Restricted ,0302 clinical medicine ,Animal science ,Endurance training ,sports nutirition ,Low carbohydrate high fat ,Dietary Carbohydrates ,Medicine ,Humans ,Elite athletes ,Special section reviews: Advances in exercise physiology: Exercise and health ,Glycogen ,business.industry ,Metabolism ,Carbohydrate ,Adaptation, Physiological ,Editor's Choice ,030104 developmental biology ,sports nutrition ,chemistry ,ketogenic diet ,Physical Endurance ,athletic performance ,business ,030217 neurology & neurosurgery ,Ketogenic diet ,Research Paper - Abstract
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: 200%) increases in exercise fat oxidation occurred in the LCHF Adaptation economy and 25 km tests, reaching mean rates of ∼1.43 g min−1. However, relative V˙O2 (ml min−1 kg−1) was higher (P, 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.
- Published
- 2020