Here is a video from what appears to be the studio recording of Love is all you need. It might be me, but it does look like John and Paul are chewing gum between their singing parts. It’s not very strange compared to all the other stuff happening there, but it appears sort of unprofessional.
Yes, John chewed a Lot of gum. In many of his vids/ concert movies I too notice he’s chewing gum. He ( as well as the other Fabs) was a smoker, so mayhaps he chose to chew rather than smoke while he played.
Yeah…they better watch it. Their careers will never get off the ground if they do stuff like that. 
I’ve seen clips of live shows where he was chewing gum. I just find it amazing that while watching him wail out “Mother” that he didn’t accidentally “fwwoooom!” his gum out of his mouth.
Now we know what Bob Dylan meant:
I said, “Your words aren’t clear,
You’d better spit out your gum.”
I’ve seen clips of Greg Lake chewing gum while singing too. I wonder if it helps lubricate the throat.
Yes, vile habit, reminds me of cows chewing cud – Sir Paul is still addicted to it.
I suppose it might, as chewing makes you salivate. I’d think drinking water between takes would be better though, you don’t want to choke on a gum on a perfect recording session.
You don’t really see many singers chew gum on their concerts. Not from what I’ve seen. On the other hand, weren’t John and Paul pretty stoic? They weren’t exactly running around.
Patti LaBelle is well-known for always having a well-chewed piece of gum in her mouth - how the hell she hits the notes she does while stashing the gum to one side is beyond me…
Hey, I sing with chewing tobacco 'tween the cheek and gum.
I remember seeing that film on TV at the time and have always considered that they weren’t actually singing but miming (“lip synching”, I believe you chaps call it).
Pavarotti chews gum during concerts. Sorry, I don’t have a cite. It’s something that Happy Rhodes said in concert once. She said she was watching him on TV and was shocked to notice that he was chewing gum. After thinking about it, she thought it was a pretty good idea to keep the saliva flowing, and started doing it herself.
If anyone’s interested (I realize no one is), here’s a bit from a different show where she mentions why she chews gum in concert (I left the song that comes after and the very funny patter later, and the gum doesn’t affect any of it at all).
No, he’s a breath mint.
They were performing with a pre-recorded backing track, but Lennon’s lead vocal was done live on the air. (The instrumentation was partly live, partly taped.)
If you watch carefully, you’ll notice that Ringo doesn’t match up exactly with what you hear the drums doing. During the verses, you can hear the snare drum going 1-2-3-4-1-2-3-4, but Ringo appears to play 1-2-3-4-1—3–. There are also a few spots where McCartney’s mouth is pointing at John instead of at his microphone, yet there is no reduction in his volume.
Pot. Kettle. Blashamizmmmmmph.
That performance of All You Need Is Love at Abbey Road Studios was the British segment of the first live worldwide satellite television broadcast, seen in 24 countries on June 25, 1967. It was originally in black and white; what you are seeing is very good computer colorized version.
The Whole World Is Watching, by Tom Huntington.
Note the close-up of Mick Jagger among the audience in the studio.
The video clip you see now has the original audio replaced by the record version. The original broadcast survives in pristine video and audio quality, and they match perfectly. They made a pre-recorded backing track and played live to it for the TV broadcast. Then later they went back and did some more work on it. If you see this clip in color, it’s the doctored version, as it was broadcast in black and white.
So John Lennon is actually repeating “She loves you, yeah, yeah, yeah” for the broadcast live version? I heard that was a spur-of-the-moment ad-lib in the original take.
Yes, he was singing that there. He had also sung it in previous takes, so it was something he had planned to do.