Supplementary Material for: Volitionally regulated breathing with prolonged expiration influences food craving and impulsivity

Introduction
Previously an intervention involving volitional slow breathing reduced trait food craving with protective effects on cardiac vagal activity (CVA). Breathing with a low inspiration-to-expiration ratio (i/e) also increases CVA. High CVA was separately associated with low unregulated eating and lesser impulsivity. Hence the present study assessed breathing with a low i/e for effects on state food craving, hunger and satiety, state impulsivity, and heart rate variability (HRV) in healthy obese persons.
Methods
Forty obese persons were randomized to two groups. The intervention group (mean age ± SD, 41.15 ± 12.63, M: F, 10:10) practiced metronome-regulated breathing with low i/e at 12 breaths per minute (expiration 72% of total breath duration) (bpm) and attained expiration 55.8% of total breath duration, while the active control group (mean age ± SD, 44.45 ± 11.06, M: F, 13:07) sat motionless and directed their gaze and awareness to the stationary metronome without modifying their breath consciously. The HRV was recorded before, during and after breathing intervention (or control) (standard limb lead I, acquisition at 2000 Hz, with a LF filter = 0.5 Hz and HF filter = 50 Hz. Time-domain and frequency-domain HRV parameters were obtained with Kubios software. State food craving, hunger and satiety were recorded before and after the intervention/control.
Results
The intervention group decreased total state food craving scores and the sub-domains (i.e., desire to eat, positive reinforcement, lack of control and hunger), increased current satisfaction with food, decreased total state impulsivity (repeated measures ANOVA, p < 0.05 in all cases), increased HF-HRV and RMSSD (linear mixed model analyses with age and gender as fixed factors; p<0.05 in all cases) during the intervention compared to the preceding baseline. The intervention group also showed an increase in positive mood and a decrease in aroused and negative mood states.
Conclusion
Changes in state food craving and impulsivity could be related to an increase in HRV or to changes in subjective relaxation and positive mood or to both.

引言
既往一项基于有意识慢呼吸的干预手段可降低特质性食物渴求，并对心脏迷走神经活动（cardiac vagal activity, CVA）产生保护作用。采用低吸呼比（inspiration-to-expiration ratio, i/e）的呼吸模式同样可提升CVA。高水平CVA分别与低水平的失控进食及较低的冲动性呈负相关。因此本研究旨在探究低吸呼比呼吸对健康肥胖人群的状态性食物渴求、饥饿感、饱腹感、状态性冲动性以及心率变异性（heart rate variability, HRV）的影响。

研究方法
本研究将40名肥胖受试者随机分为两组。干预组（平均年龄±标准差：41.15±12.63岁，男女性别比10:10）采用节拍器调控的低吸呼比呼吸训练，呼吸频率为12次/分钟，呼气时长占总呼吸时长的72%，实际完成的呼气时长占总呼吸时长的55.8%；而主动对照组（平均年龄±标准差：44.45±11.06岁，男女性别比13:7）保持静坐姿，将视线与注意力集中于静止的节拍器，不会有意识地调整自身呼吸模式。心率变异性的记录覆盖干预（或对照）前、干预中及干预后三个阶段，采用标准肢体导联I，采样频率为2000Hz，低通滤波器（LF）截止频率设为0.5Hz，高通滤波器（HF）截止频率设为50Hz；采用Kubios软件提取时域及频域心率变异性指标。分别于干预/对照前后记录状态性食物渴求、饥饿感及饱腹感评分。

研究结果
与干预前基线水平相比，干预组的总状态性食物渴求评分及其各子维度（即进食欲望、正性强化、失控感及饥饿感）均显著降低，当前食物满意度显著提升，总状态性冲动性显著降低（重复测量方差分析repeated measures ANOVA，所有指标p均<0.05）；同时干预组的高频心率变异性（high-frequency heart rate variability, HF-HRV）及连续间期差值均方根（RMSSD）显著升高（以年龄和性别为固定因素的线性混合模型linear mixed model分析，所有指标p均<0.05）。此外，干预组的正性情绪评分显著升高，唤醒型负性情绪评分显著降低。

结论
状态性食物渴求与冲动性的改变，可能与HRV升高、主观放松感及正性情绪的改善相关，或与上述因素共同作用相关。