When I first started using amphetamines, I used them whenever, and I never had any appetite. No eating, plus plenty of activity, meant my weight went down.
Temporarily.
Later on, I was always mornings only and still if I score, I use it in the mornings. I eat breakfast first.
By noon I would be hungry enough to eat a light lunch. By dinner I would be hungry enough to eat an average size meal.
I get up early and I've had trouble waking up in the a.m. since I was a kid. If I have a little meth to get me out the door, it's helpful but the effects wear off by midday. My tolerance is up because I overused the substance in past. Eating, wearing off midday, sleeping fine at night, are all signs that my tolerance is up.
My use is therefore down to near nothing. Meth works better than a five hour energy drink for me, to get me started in the a.m. but I can talk myself into believing I just had a couple bumps when the sun hasn't come up yet and I'm getting ready to go. If I can't seem to pull my ass out of bed, I can usually imagine the physical effects snorting a line and get that taste in the back of my throat. That works for me.
Phantom meth. For when you just can't get your day started. %)