Knowledge: The cause of obesity is being born with a certain DNA that creates more fat than usual but no doctors never know exactly what the reason still is. On the other hand, chronic fatigue can happen from biological, genetic, infectious, or psychological mechanisms.

Conversation:
Do you know what chronic fatigue syndrome is?
I know that the fatigue is not because of exertion or some other medical condition. It's essentially unexplained.
Any idea what causes it? I have heard about it but never know what it is.

Response: Yeah, the cause of chronic fatigue can be biological, genetic, infectious, or psychological mechanisms..