Burke L M, Angus D J, Cox G R, Cummings N K, Febbraio M A, Gawthorn K, Hawley J A, Minehan M, Martin D T, Hargreaves M
Sports Science and Sports Medicine, Australian Institute of Sport, Belconnen 2616, Australia.
J Appl Physiol (1985). 2000 Dec;89(6):2413-21. doi: 10.1152/jappl.2000.89.6.2413.
For 5 days, eight well-trained cyclists consumed a random order of a high-carbohydrate (CHO) diet (9.6 g. kg(-1). day(-1) CHO, 0.7 g. kg(-1). day(-1) fat; HCHO) or an isoenergetic high-fat diet (2.4 g. kg(-1). day(-1) CHO, 4 g. kg(-1). day(-1) fat; Fat-adapt) while undertaking supervised training. On day 6, subjects ingested high CHO and rested before performance testing on day 7 [2 h cycling at 70% maximal O(2) consumption (SS) + 7 kJ/kg time trial (TT)]. With Fat-adapt, 5 days of high-fat diet reduced respiratory exchange ratio (RER) during cycling at 70% maximal O(2) consumption; this was partially restored by 1 day of high CHO [0.90 +/- 0.01 vs. 0.82 +/- 0.01 (P < 0.05) vs. 0.87 +/- 0.01 (P < 0.05), for day 1, day 6, and day 7, respectively]. Corresponding RER values on HCHO trial were [0. 91 +/- 0.01 vs. 0.88 +/- 0.01 (P < 0.05) vs. 0.93 +/- 0.01 (P < 0.05)]. During SS, estimated fat oxidation increased [94 +/- 6 vs. 61 +/- 5 g (P < 0.05)], whereas CHO oxidation decreased [271 +/- 16 vs. 342 +/- 14 g (P < 0.05)] for Fat-adapt compared with HCHO. Tracer-derived estimates of plasma glucose uptake revealed no differences between treatments, suggesting muscle glycogen sparing accounted for reduced CHO oxidation. Direct assessment of muscle glycogen utilization showed a similar order of sparing (260 +/- 26 vs. 360 +/- 43 mmol/kg dry wt; P = 0.06). TT performance was 30.73 +/- 1.12 vs. 34.17 +/- 2.48 min for Fat-adapt and HCHO (P = 0.21). These data show significant metabolic adaptations with a brief period of high-fat intake, which persist even after restoration of CHO availability. However, there was no evidence of a clear benefit of fat adaptation to cycling performance.
八名训练有素的自行车运动员连续5天随机摄入高碳水化合物（CHO）饮食（9.6克·千克⁻¹·天⁻¹ CHO，0.7克·千克⁻¹·天⁻¹脂肪；HCHO）或等能量的高脂肪饮食（2.4克·千克⁻¹·天⁻¹ CHO，4克·千克⁻¹·天⁻¹脂肪；脂肪适应），同时接受监督训练。在第6天，受试者摄入高碳水化合物并休息，然后在第7天进行性能测试[以最大耗氧量（SS）的70%进行2小时骑行+7千焦/千克计时赛（TT）]。采用脂肪适应饮食时，5天的高脂肪饮食降低了在最大耗氧量70%时骑行期间的呼吸交换率（RER）；1天的高碳水化合物饮食使其部分恢复[第1天、第6天和第7天分别为0.90±0.01、0.82±0.01（P<0.05）、0.87±0.01（P<0.05）]。HCHO试验中的相应RER值为[0.91±0.01、0.88±0.01（P<0.05）、0.93±0.01（P<0.05）]。在SS期间，与HCHO相比，脂肪适应饮食时估计的脂肪氧化增加[94±6克对61±5克（P<0.05）]，而CHO氧化减少[271±16克对342±14克（P<0.05）]。示踪剂衍生的血浆葡萄糖摄取估计值显示各处理之间无差异，表明肌肉糖原节省导致CHO氧化减少。对肌肉糖原利用的直接评估显示出类似的节省顺序（260±26对360±43毫摩尔/千克干重；P = 0.06）。脂肪适应饮食和HCHO的TT成绩分别为30.73±1.12分钟和34.17±2.48分钟（P = 0.21）。这些数据表明，短时间的高脂肪摄入会导致显著的代谢适应，即使在恢复CHO供应后这种适应仍会持续。然而，没有证据表明脂肪适应对自行车运动表现有明显益处。
