Why are people who do Yoga so thin?

There are countless benefits to practising yoga. These include improved flexibility and posture, more strength, better balance and a heightened state of relaxation and awareness. However, does it really work the heart and lungs in the same way as a good cardio workout and does it burn a lot of calories?

The short answer is no. It doesn't.

Scientific evidence suggests that even the most intense yoga classes such as Power Yoga or Ashtanga Yoga will not increase your heart rate and Vo2 max sufficiently enough for it to be classed as cardio. Yes, some routines may leave you slighly out of breath and your muscles will get tired but intense yoga sessions still fail to meet minimal aerobic recommendations as its oxygen demands represent relatively low physical activity. However, for unfit, sedentary individuals, 10 minute sun salutations may improve cardio respiratory fitness to some degree.

But many people who practise Yoga are thin, therefore it must burn lots of calories?

This is where yoga gets a little more complicated. Yoga on average burns around 150 calories, the same as a slow walk. However, regular yoga practitioners enter a state that we call hypometabolism. This is were the body actually lowers its basal metabolic rate by 13% (calories burned per day lower by 13%). With this in mind you might think wow, if I am burning less calories surely I will put on weight. Well, this could be true but yoga practice positively affects the mind . The body and mind of a seasoned yogi start to require less food to surivive. Therefore, the body's desire and craving for food and junk food changes/reduces (possibly due to the psychological effect of reduced stress or better hormone balance). This logically equates to less consumption of calories in a sensible, physiologically aware individual, and therefore eventual weight loss. This is likely to be a very slow process and would require patience from the practitioner, but it is certainly possible if practiced with dedication everyday.

All in all, yoga has many primary benefits including hormone balance, improved blood pressure, reduced stress and depression and increased strength and flexibility; but these benefits are completely unrelated to calories burned and cardio. My personal recommendation would be to still incorporate weights and cardio into a weekly yoga routine to give the heart that little bit of extra activity.

References:

The Science of Yoga by William J Broad

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