I would take the focus off the food, i.e. no more giving or witholding treats. Just don't even buy the stuff.
I don't! It was all Halloween stuff. Even the candy before Halloween was given to us. I had it out to give to guests so that none of us would eat it!
(Okay, I will confess that the chips I bought for me because I'd been craving them.

But the kids saw 'em, so I was sharing.)
The trouble is that they had a HUGE haul of Halloween candy (Thanks, DH...You couldn't have ended the evening early? *sigh*), and I only allow them each 3 pieces of candy per day, and then only after they eat a good dinner.
Honestly, junk is NOT the norm around here!
Besides, I have a feeling that if it weren't this, he'd be lying and sneaking something else...