I deal with fatigue a lot... can't sleep and all that... but another thing I've slowly come to realize, is my inability to gain weight, and my constant need to eat. I'm starting to wonder if my body is absorbing the nutrients and calories it needs to fully function.

All my life I have been skinny, and I've always eaten generous quantities of food, sometimes to the shock of others... and yet I have never gained any weight. I have experimented with dozens of Krispy Kreme donuts, potato chips, fast food, as well as very healthy home cooked meals... and there is NO DIFFERENCE in my energy levels or weight.

The only way I can gain a few pounds is if I lift weights... I assume because it is forcing my body to absorb more nutrients to build muscle. However, even then I hit a ceiling of sorts where no matter how much protein I take in, I can't break through.

Is this a disorder of sorts? I have seen it mentioned once elsewhere on the internet (just a random find), though I'm having trouble finding it again.

Have you been to a yearly physical lately? Could be a thyroid issue, could be just the way your body works, but s/he would know what to look into. For the fatigue, it might just be a case of low iron. For women that's not unusual, many need to add folic acid. For men it's not so common, especially if you're eating meat.

I'm not a doctor, but I play one on tv (I've always wanted to say that) ... seriously, that's just what came to mind. A physical would be more revealing.