It is ironic that during this first few months of extreme growth, owners tend to give too little food and malnutrition occurs. Many new owners have the misconception that, like goldfish, overfeeding will cause problems, and some are even silly enough to think that eating more produces more excrement and hence by feeding less, less mess is produced.

I debunk such falsehoods by challenging owners to imagine doubling their own weight in six weeks. I don't recommend trying it, but you can imagine you have to pretty much eat constantly to do this.

When a dog or cat reaches around six to seven months of age, much of the growth spurt of puberty has slowed drastically and this is when owners need to decrease the amount of food, which often doesn't happen. This is the first dangerous phase of a dog or cat's life where obesity can creep in.

There is a myth that this weight gain is caused by the neutering surgery that is coincidentally best done at this age. Neutering will cause mild weight gain, just like when people quit smoking or start taking birth control pills, but that alone will not cause obesity.

The second dangerous phase of weight gain is ageing, so the older your pet gets the easier it will get fat. It's not just a problem with metabolism. Many animals don't have perfect joints and different breeds will have problems to varying degrees; it is almost an inevitable part of growing old. This initially minor joint pain causes decreased mobility and has the snowball effect of causing weight gain, which then worsens the arthritis and it can become a vicious circle.

Surprisingly, dogs can suffer from various degrees of arthritis at any age. I have seen a fat one-year-old golden retriever this week that cannot walk because of severe arthritis caused by congenital hip problems and obesity.

People and animals have been poorly designed for the modern age. Our bodies were designed for a time when food sources were scarce and irregular. During times of plentiful food, getting obese may have resulted in a survival advantage of storing excess energy during times of famine.

In this modern era of three or more meals a day, with our less active lifestyles, most people would struggle not to get fat. As I have aged, I have started to record my weight daily, so it reminds me to keep an eye on my health. I recommend the same for owners to do so with their dogs, as weight gain can be insidious.

The list of problems caused by obesity seems to grow every year. Larger dogs are more predisposed to arthritis and smaller dogs, especially the toy breeds that are popular in Hong Kong, are predisposed to some life-threatening lung diseases. In short, a fat dog will have not only a shorter, less active life, but the related health problems will cost owners heartache, money and time.

It is much easier to help a dog lose weight than it is for people, as the control is totally in an owner's hands. It is prudent to seek veterinary advice before starting any diet, as some medical conditions may need to be addressed first.

Also, ask your vet for a target weight, then my general advice for dogs is to cut out all snacks, make sure your pet is being fed a good commercial diet, cut 20 per cent off the regular serving and monitor your pet's progress. If there little progress is recorded, then take another 10 per cent off in the next month, and so on. For overweight cats, I recommend that owners seek a vet's prescription diet, as rapid weight loss in fat cats can lead to liver problems, and more control is needed.

When your hungry dog or cat begs for food, don't cave in. You don't need to reward your pet with food; attention, play time, walks and pats are often reward enough.