Energy - and simple tests - for breatharians

Those claiming to be breatharians claim to derive energy directly from their alternative source - e.g. the spiritual energy prana. 

They claim they do not eat, since they don't need food for energy.  Hence, they wouldn't have fuels such as glucose, derived from food, in their blood. 
This is one simple test a doctor could run on a breatharian: a blood test for the absense of glucose

In the previous post, I showed how oxygen is used in our bodies to help metabolise glucose, forming carbon dioxide as a useless by-product. 

Those claiming to be breatharians claim their cells receive energy directly from prana, and the prana also creates whatever else they need, when they need it.  They claim their bodies are very pure, and don't create useless products.  As carbon dioxide is useless to humans, a breatharian would not be forming or breathing out carbon dioxide. 
This is a second simple test for breatharianism: a test for the absense of carbon dioxide in their breath.

Normal people only have to breathe because oxygen is essential for metabolising food.  So, paradoxially, absense of breathing might have been another test for whether a breatharian really managed to do without the energy derived from food.  However breatharians do claim to still need to breathe for a different reason: in order to derive nutrients, or to absorb prana into their body - the lungs, in effect becoming a breatharian's equivalent of the stomach.