Mayasandra S. Chaya.
Assistant Professor, Swami Vivekananda Yoga Research Foundation, Bengaluru, India
chayapu@hotmail.com

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Abstract

While yoga is thought to reduce the risk of chronic non-communicable diseases such as diabetes, there are no studies of insulin sensitivity in long term practitioners of yoga.
We assessed insulin sensitivity and cardiac autonomic function in long term practitioners of yoga. Fifteen healthy, young, male practitioners of yoga were compared with 15 young, healthy males who did not practice yoga matched for body–mass index. Fasting insulin sensitivity was measured in the fasted state by the hyper insulinaemic euglycaemic clamp. There were no significant differences between the groups in their anthropometry or body composition. However, the fasting plasma insulin was significantly lower in the yoga group.
The yoga group was also more insulin sensitive (yoga 7.82 [2.29] v. control 4.86 [1.97] (mg/(kg.min))/(ìU/ml), p<0.001). While the body weight and waist circumference were negatively correlated with glucose disposal rate in the controls, there were no similar correlations in the yoga group.
The yoga group had significantly higher low frequency power and lower normalized high-frequency power. Long term yoga practice (for 1 year or more) is associated with increased insulin sensitivity and attenuates the negative relationship between body weight or waist circumference with insulin sensitivity.
Sympathetic tone and enhanced vagal activity.15,16 Further, an increase in baroreflex sensitivity has been documented with the practice of yoga including meditation or prayers.17 Plasma nor epinephrine levels have been shown to be reduced in patients with cardiac failure after yoga training18 and urinary catecholamines have been shown to be significantly reduced in long term practitioners of yogic asanas.19 Finally, yoga has been found to be useful in reducing IR-related risk factors.20 These studies have mainly been performed on older, obese, frankly hypertensive or diabetic subjects; moreover, many studies have used surrogate measures of IR such as the homeostatic model assessment (HOMA) or fasting plasma insulin or glucose levels.
Careful studies that measure IS in young adults who routinely practice yoga are necessary because (i) type 2 diabetes mellitus in India is increasingly being reported in young adults and children,21,22and (ii) this brings a prevention-oriented, culturally acceptable, lifestyle paradigm to bear on the problem. While there are no detailed interventional studies using yoga to test the hypothesis that yoga improves IS, we undertook a pilot study to measure IS in normal young healthy volunteers who routinely practised yoga for more than 12 months in comparison with BMI-matched non yoga practitioners, using the hyper insulinaemic euglycaemic clamp (HEC) technique.