Some drugs are appetite suppressants. Does this mean they suppress feelings of hunger, or rather, does it mean they suppress the desire to eat? (Or both or neither?)
Well most of them are stimulants which give you energy and supress hunger, also the energy they give you makes it less likely you will notice low blood sugar etc.
There is a herb called Hoodia cactus that claims it supresses hunger without being a stimulant, so presumably you would still feel fatigued and tired if you go long enough without eating.
This. That is, yes to both questions, since they’re kind of linked.
I was interested if they actually speed up your metabolism, and I was told they don’t.
Once I started taking them, I felt gross, incredibly full after just a normal meal. After about a week my body (and behavior) started to put two and two together, and I eat a terrific amount less.
Warning, anecdote ahead:
For a little while several years back, my psych gave me Topomax for its off-label purpose due to some weight/food issues (it’s actually an anti-migraine, anti-seizure drug – but an extremely common side effect is loss of appetite). I took it for about three weeks and man, it worked – I literally had no hunger and ate almost nothing for days until I realized that wasn’t good either, so I just sorta forced down three regular smallish meals; Otherwise I just couldn’t be bothered to eat. It was awesome. 
I mean, food suddenly became just sustenance, not a source of comfort/joy/numbness as it had been. Basically I suddenly had a proper perspective on food.
Unfortunately one other (rare) side effect is blurry vision that can lead to acute narrow angle glaucoma, and one day I suddenly found myself finding it difficult to focus my vision. I couldn’t get in touch with my doc and checking the medicine’s warnings I spotted the glaucoa warning with an exhortation to go to the ER immediately if eye problems arose. So off to the hospital I went, and that was the end of my Topomax experiment.
(As it turns out, while the eye doc was testing my vision, he noticed I had an astigmatism–something I’ve never been aware of. I’m not certain whether I was just suddenly aware of the astigmatism or if this was a genuine Topomax side effect. But either way the doc didn’t want to risk it and ordered me off the drug.)
Sooooo anyway, that’s what at least one appetite suppresant does: stopped hunger and the urge to eat despite not being hungry (which is the problem with many people with food issues, obviously).
a long time ago, i took something that is supposed to help with my appetite. it gave me hunger pangs but not an appetite.