DataDave said:

Mood changes on mental health: I want to be transparent — I went through a rough patch emotionally around month 4.

This is where I part company with the consensus forming above. I would be careful about how confidently the flatness reports get attributed. Rapid weight loss, a large deficit and disrupted sleep produce low mood on their own, and separating that from a drug effect is genuinely hard.

pete_manc_UK said:

The weight came off and the harder part started, which is not what any of the material I read had prepared me for.

Anxiety increase on mental health: counterintuitive, but losing weight rapidly triggered anxiety for me. Change — even positive change — is stressful. I was anxious about whether I deserved to feel good.

This is more common than people admit. A therapist who specializes in weight management has been invaluable. Don't neglect the mental health side of this journey.

TirzTom said:

I would be careful about how confidently the flatness reports get attributed.

Body image adjustment with mental health: I've lost 55 lbs but when I look in the mirror, I still see my old self sometimes. "Phantom fat" is a real phenomenon.

My therapist specializes in body image issues with weight loss patients. She says it can take 12-18 months for your brain's body map to update. In the meantime: take progress photos (your eyes lie but cameras don't), try on old clothes, and be patient with yourself.

One thing that is still open after roxy_nash’s answer:

How would you tell the difference between that and the alternative explanation?

Closing the loop on my own question.

Update: I got the sleep and the intake sorted before deciding it was the drug, and most of the flatness went with them. Not all of it, and I am watching the rest.