Dr Johnson writes a brief article with video of the phenomenon, as an explanation for why overweight cats often "chew the air" (and anything else they can reach) when you scratch the top of their tails.
Here's a link to "My Cat Bites Me or The Air When I Scratch His Tail Top"
Excerpted from this candid and accurate article:
"When a dog is eventually at a healthy weight it will get PICKY about dry dog food. If we left it at that, our dogs would never get fat.
At that point it’s your call whether you mix something in the dry food to coaxe a lean dog to eat, or simply let her eat per her needs, and stay lean.
“She stopped liking her food. She just wouldn’t eat it.”
This is because they don’t NEED many calories when they’re mostly indoors, lean and healthy."
Dr Johnson goes over how a dog should eat and describes the "figure" most dogs should have. This makes it easier for owners of "heavy" dogs to recognize the problem.
Here's the "How Your Dog Should Eat" Article on DrJohnson.com