On a Saturday morning at Four Paws K9 Training, a big obedience club in Melbourne's north-west, a couple arrive for class carrying their small fluffy dog. Because it doesn't like to walk. Another young chap is there with his big Lab-cross because it's developed some behavioural issues, but he's uneasy. He's not sure he "believes" in training. He doesn't like telling his dog what to do. Others wonder why their dog doesn't like other dogs, or won't listen to them, or won't stop jumping on people, or pulling on the lead. About half the human students struggle to speak to their dogs in anything other than a pleading murmur. "Twenty-odd years ago the mindset was quite different," says Trish Harris, a dog trainer and owner of Four Paws. "When I started out, a dog was a dog. It had to be obedient. They lived in the family but it was a little bit more balanced. Over time what we've seen is a lot of these dogs becoming surrogate children. "When I tell them 'you need to give the dog clear instructions, you need to set boundaries and enforce them' they say, 'Won't he stop loving me?' or 'Won't he stop listening?' I say, 'well, he's already not listening'." The AMA report also has some pretty staggering figures on expenditure. Australians spent more than $12 billion on pets and pet products in 2016. A third of that, $4 billion, was for dog food with another $1 billion for doggy accessories but just $274 million was spent on training.Yet if there's one really crucial, I'll-do-anything-for-my-dog thing you can do for your fur baby, it's to undertake proper obedience training.

A lot of the issues Harris sees in her classes are with the toy breeds – pugs, poodles, dachshunds. Because the dogs are small and adorable they're allowed to get away with murder. But she sees the same problems with people who have adopted from a shelter. In an effort to compensate for what they imagine was the dog's previous life, they go all out to be kind. "Our maternal instincts come out and we want to mollycoddle and love it and protect it. Which is great. But it can have the opposite effect. It can turn the dog into a really nasty, uncontrollable, undisciplined aggressive dog." Barking, jumping, lunging, snarling, snapping and biting are not signs of a "naughty" dog, and certainly not simply a high-spirited one. They are almost always the sign of a dog that has never been taught how to get on in the world, and as a consequence is experiencing a lot of stress. It sounds like heresy but after two decades in the business and a wealth of study and observation, Harris says dogs don't actually want our love – or not in the ways we tend to show it. "They want your guidance. They want to feel safe. They need structure, and they're the things people don't think of giving."

And while she would say this – she's a dog trainer, after all – the science backs her up. Happy dogs are well-trained dogs, or at least dogs that live in a world with consistent rules and routines. "Dogs don't understand grey areas," Harris says. "They can either always do something, or they can never do something. And once a dog understands that, he feels safe and happy." Dogs aren't people. But in the 21st century a lot of them are suffering from a similar malaise to their owners. They don't get enough exercise, and they eat too much. Obesity in a dog is every bit the problem it is in a human. It puts stress on the skeleton and on the joints, on the heart and lungs, it makes moving and breathing difficult. In the US, things are so bad there's an Association for Pet Obesity Prevention, which estimates 54 per cent of that nation's dogs are obese. It's unlikely things are much better here. "Too much food, too much 'love'," says Kerri Bradley, a dog trainer with a particular interest in canine nutrition. The most common issue she sees is simple over-feeding. A beloved pet gazes at you longingly.What do you do? Hand over a snack, of course.

"I also see problems with the kinds of things people are feeding their dogs, especially processed foods," says Bradley. Dogs are not humans. While we know, just looking at them, that their physiology is completely different from ours, we don't always factor that in when we're choosing their dinner or their treats. Dogs' teeth are designed for ripping and tearing, not grinding. Their gut has a higher acid content, to digest fur and bone. Their mouths don't produce amylase, the enzyme that helps process carbohydrate. Unfortunately, the perfect canine diet looks pretty repulsive to most people, which is a problem if we've grown to think of our dogs as furry, funny-shaped humans. Raw meat, raw offal, meaty bones, finely shredded raw veg – that's a dog's idea of fine dining. One feature dogs unfortunately do share with people is "sweet" receptors on their tongues. Dogs get as addicted to sugary treats as we do. We also get just as sucked in by pet food marketing as we do with our own treats and snacks. "People see the cute ads, and think I'll get that for my dog. But a lot of these treats have a lot of sugar in them. Of course the dog loves them, but that kind of food isn't doing your dog any favours," Bradley says. But not giving your fur baby something it thinks is yummy? It's a tough ask. "Even my mum does it, I'm ashamed to say," says Bradley.

Perhaps one of the strangest trends in modern dog ownership is playing dress-ups with our dogs. Tim Munro is a trainer and behaviourist who specialises in a form of dog physical therapy called Tellington TTouch.While he concedes some dogs are temperamentally better equipped to handle being corseted than others, it's an area where, for our dogs' sake, we should be proceeding with caution. "I absolutely don't think it's automatically bad," Munro says. "But I do see a lot of people who think their dogs are fine but I'm seeing things in the dog's body language that show it's not OK." The feeling of constriction produced by being strapped into a decorative vest clothing can activate the sympathetic nervous system, the fight/flight/freeze response. A dog that starts running around like a loon when it's dressed up is probably not enjoying itself. There are more subtle signs, too. "Sometimes you put something on a dog and the dog suddenly goes really quiet," Munro says. "You think that's good but in fact the dog might have just frozen, completely shut down."

You see that a lot in those YouTube videos of dogs in Halloween costumes: motionless except for their bulging eyes and anxiously flicking tongues. You may be laughing, but that's a very unhappy dog. Professor Paul McGreevy, a vet and animal behaviour specialist at the University of Sydney, is a big fan of treating dogs as dogs. In her influential bestseller Inside of a Dog, cognitive scientist Alexandra Horowitz talks about umwelt, the world as it's perceived by a particular organism. McGreevy talks about a dog's telos: its purpose, its reason for being. What McGreevy and Horowitz are both saying, in essence, is instead of imagining that your dog is human, imagine what it might be like if you were the dog. "We assume that their needs are the same as our needs, but that's not the case," McGreevy says. "Dogs have evolved to be dogs. So canine company, rules and routines that facilitate their ability to spend time out of the house, to access other social groups including other dogs – that's what they need." In other words, training – so you can be confident about having your dog out and about. Lots of time with other dogs – providing the dogs get along. Vigorous exercise. And plenty of opportunity to sniff stuff. That's how you get a happy dog. And a happy life.

McGreevy says the key to being a good "fur parent" (although he would never, in this life or the next, use that term) is to establish a relationship where we're relevant to the dog, without needy co-dependence. "That's the critical blend or balance. Being there for the dogs, being the social group member that the dogs look to for activity, fun, excitement. Without them being entirely dependent on us." So staging a birthday party for your dog could actually be a great thing to do – as long as it gets along with the other guests and you're not feeding it chocolate eclairs. (You could probably leave off with the party frock, too.) Taking your dog everywhere with you is terrific – just don't carry it around in your handbag. "People are very well motivated," McGreevy says. "We just need to tweak things a bit." Melinda Houston is a Fairfax Media television critic and is studying to be a dog trainer.