Department of Exercise Science, Brigham Young University, Provo, UT.
Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT.
Med Sci Sports Exerc. 2021 Sep 1;53(9):1987-1998. doi: 10.1249/MSS.0000000000002655.
This study assessed β-hydroxybutyrate (BHB) concentration during a short-term fast and the degree to which an initial bout of exercise influences the rate of ketogenesis.
Twenty subjects (11 male, 9 female) completed two 36-h fasts, with one protocol requiring the subject to complete a treadmill exercise session at the beginning of the fast. BHB levels were assessed via portable meter every 2 h, along with mood and hunger ratings. Venipuncture was performed every 12 h.
The mean (SD) areas under the curve for BHB concentration were 19.19 (2.59) mmol·L-1 (nonexercised) and 27.49 (2.59) mmol·L-1 (exercised), yielding a difference of 8.30 mmol·L-1 between conditions (95% posterior probability interval (PPI), 1.94 to 14.82 mmol·L-1; posterior probability (PP) = 0.99). The mean (SD) times to BHB concentration of 0.5 mmol·L-1 were 21.07 (2.95) h (nonexercised) and 17.5 (1.69) h (exercised), a 3.57-h difference (95% PPI, -2.11 to 10.87 h; PP = 0.89). The differences in area under the curve between conditions were 5.07 μU·mL-1 (95% PPI, -21.64 to 36.18 μU·mL-1; PP = 0.67) for insulin, 97.13 pg·mL-1 (95% PPI, 34.08 to 354.21 pg·mL-1; PP = 0.98) for glucagon, and 20.83 (95% PPI, 4.70 to 24.22; PP = 0.99) for the insulin/glucagon ratio.
Completing aerobic exercise at the beginning of a fast accelerates the production of BHB throughout the fast without altering subjective feelings of hunger, thirst, stomach discomfort, or mood. Insulin and the insulin/glucagon ratio experience a marked reduction within the first 12 h of fasting and was not altered with exercise. Thus, exercising at the beginning of a fast may improve the metabolic outcomes of fasting.
本研究评估了短期禁食期间β-羟丁酸（BHB）的浓度，以及初始运动对酮体生成速率的影响程度。
20 名受试者（11 名男性，9 名女性）完成了两次 36 小时的禁食，其中一项方案要求受试者在禁食开始时进行跑步机运动。通过便携式仪表每 2 小时评估一次 BHB 水平，并评估情绪和饥饿感评分。每 12 小时进行一次静脉采血。
BHB 浓度的曲线下面积平均值（SD）分别为 19.19（2.59）mmol·L-1（无运动）和 27.49（2.59）mmol·L-1（运动），条件之间的差异为 8.30 mmol·L-1（95%后验概率区间（PPI），1.94 至 14.82 mmol·L-1；后验概率（PP）=0.99）。BHB 浓度达到 0.5 mmol·L-1 的平均（SD）时间分别为 21.07（2.95）h（无运动）和 17.5（1.69）h（运动），差异为 3.57 h（95%PPI，-2.11 至 10.87 h；PP=0.89）。条件之间的曲线下面积差异分别为胰岛素 5.07 μU·mL-1（95%PPI，-21.64 至 36.18 μU·mL-1；PP=0.67），胰高血糖素 97.13 pg·mL-1（95%PPI，34.08 至 354.21 pg·mL-1；PP=0.98）和胰岛素/胰高血糖素比值 20.83（95%PPI，4.70 至 24.22；PP=0.99）。
在禁食开始时进行有氧运动可以加速整个禁食过程中 BHB 的产生，而不会改变饥饿、口渴、胃部不适或情绪的主观感觉。在禁食的前 12 小时内，胰岛素和胰岛素/胰高血糖素比值明显下降，而运动并未改变。因此，在禁食开始时运动可能会改善禁食的代谢结果。
