"Did you hear about the new low-fat religion?…

“I can’t believe it’s not Buddha!” is a pun on “I Can’t Believe It’s Not Butter!” that has been printed on many images. Buddha is often depicted as fat.

“Did you hear about the new low-fat religion? ‘I Can’t Believe It’s Not Buddha’” was posted on Twitter by English Muffin on July 7, 2013.

“A Tibetan monk sees Jesus in a tub of margarine and cries, ‘I can’t believe it’s not Buddha!‘“ is a related joke.

Wikipedia: I Can’t Believe It’s Not Butter!
I Can’t Believe It’s Not Butter! is a spread brand produced by Upfield and marketed as a substitute for butter.

Wikipedia: Gautama Buddha
The Buddha (also known as Siddhattha Gotama or Siddhārtha Gautama) was a philosopher, mendicant, meditator, spiritual teacher, and religious leader who lived in Ancient India (c. 5th to 4th century BCE). He is revered as the founder of the world religion of Buddhism.

Twitter
English Muffin
@laurascaz
Did you hear about the new low-fat religion?
“I Cant Believe Its Not Buddha”
THANK YOU! I’ll be here until someone puts me out of my misery
8:41 PM · Jul 7, 2013·Twitter for Android

Twitter
Julia Charnley
@JuliaCharnley
Did you hear about the new low-fat religion? “I Cant Believe Its Not Buddha”
10:59 AM · Jan 30, 2014·Facebook

Twitter
Caitlin Quinlan
@caitlinquinlan
Q: Did you hear about the new low-fat religion? A: “I Cant Believe Its Not Buddha. http://fb.me/48LEstjxO
7:10 AM · Apr 15, 2015·Facebook

Twitter
Bob Kostic
@causticbob
Q: Did you hear about the new low-fat religion?
A: “I Cant Believe Its Not Buddha”
3:25 PM · May 29, 2016·Twitter Web Client

Twitter
MidNightMan
@MidNigh62320582
@CowardlyMajor
Hey Ari i got a joke for ya.
Did you hear about the new low-fat religion?
“I Cant Believe Its Not Buddha”
2:31 AM · Nov 25, 2018·Twitter for Android