Fatigue. The beast that hits people with many ills.

The word Asthenia is also used... where something else may sit. 

For what is it when it hits, whats behind it?
I can Identify at least contributors to why i get *whacked out* 7 or 8 at a push. 
Others dont get the DX's that tell them what is causing this loss of energy. 
Mine comes from bowel disease, two things to do with my blood , at least, one of my tablets, and a thing also thats #mh based, and some organ damage. Theres other suspects too. 
But core to that is a chronic infection. 
Where my system, and the main tablet both SLOW ME DOWN, is that the right description? 
Many contributions to it. Add the Seventh of Low appetite leading to low energy too, which is a spin off from three aspects described above. Very complex. But if you look Holistically, theres no way i can bounce around like some can. Now its not been Called Chronic Fatigue Syndrome from any practitioner ive seen, but Im tired almost constan, and exhausted at other times.Far more than someone without these conditions described. 
Some say CFS doesnt exist for these reasons. 
And that it describes the complex interaction of various ills and conditions. But yes the link to infection is a given, and is it the be all and end all that it is from infection? No i dont think it is. I believe CFS is a broad church term, when docs are either too lazy to find root of it or its unknown land for reason.
This doesnt touch at all on muscle wasting or genetic diseases,of a degenertive nature.. thats not in these thoughts, but they too get the CFS label in a lot on instances.