There also hasn't been any evidence of any serious bad effects.
That seems to be the case.  It also looks like evidence has shown that there's no adverse effects from trying to counteract the effects of CFS, which is good.
I have quite a lot of energy, but I know some people just aren't as lucky. Is their a medical condition for being constantly tired? There is a condition called chronic fatigue syndrome in which people have long-term fatigue in a way that limits daily activity. That must be awful. I wonder what causes it. Depression perhaps? I don't think the cause is fully understood.  It could be genetic, could be biological, or it could be psychological. Well, I guess the medical profession had better get to the bottom of it. It must be destroying people's lives! I wouldn't know, but there is some evidence that cognitive behavioral therapy combined with increasing activity can help. That makes sense. If a person exercises it often brings ones energy levels up.
In a systematic review of exercise therapy, no evidence of serious adverse effects was found; however data was insufficient to form a conclusion.