The Saturation effect doesn't work as a custom potion: /give @p minecraft:potion{CustomPotionEffects:[{Id:23,Duration:3600}]}
However using the command works as expected: /effect give @p 23 3600
This appears to be a reversion of MC-112389
Linked issues
duplicates
Comments

Thank you for your report!
We're actually already tracking this issue in MC-142061, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki
Also, Jira has code tags, but they work like this: {code}<text>{code
}

Thanks for the tip about Jira. I only just now noticed that there are two separate dropdowns for "extra" tags. WTG Jira.
I definitely did use the search feature, which is how I linked the old issue. This is also literally just a regression of the old issue. Previous to minecraft 1.11 the custom potion effect for saturation worked exactly as expected. Go ahead and try it in 1.7.10
/give @p minecraft:potion 1 0 {CustomPotionEffects:[{Id:23,Duration:3600}]}
The old ticket is marked as resolved, and yet the issue still exists.
Yes, the point is, the potion actually works, just the duration is not applied (i.e., when you drink it, you gain half a hunger icon). That's what MC-142061 is about.
Sorry for all of the janky edits. Jira doesn't have a decent <code> tag, and the previews didn't match the final ticket.