At least, that was the finding of researchers in Australia, where 40 percent of households have just such a companion - the family dog. But those Australian dogs seldom get the opportunity to encourage or accompany their owners on any kind of activity.

In fact, the majority of those pooches are prisoners of their owners' sedentary lifestyles. No amount of furry fervor seems very effective at getting the owners to walk those dogs, even though it would be good for everyone involved.

Investigators from the University of New South Wales wrote in the Medical Journal of Australia that the fitness impact of dog walking has been ignored by researchers. They say their study offers a strong public health argument for increased dog walking.

With more than 65 million canine companions overall, Americans easily lead the world in dog ownership. However, Americans also lead the world in obesity, and public health advocates have wrangled with various ideas to get Americans to eat less and move more. Could the Aussies be on to something?

Here's what they found: Of almost 1,000 randomly sampled adults in New South Wales, the researchers reported that less than half achieved the U.S. surgeon general's recommended 150 minutes of exercise every week.

Most dog owners in the study were actually less likely than the non-owners to get their 150 minutes of exercise, either with or without Fido at their side. Most spent less than an hour a week actually walking with their dog. Fully 59 percent said they never walked their dog at all. Some 26 percent said they walked the dog up to two and a half hours over a week, and only 15 percent said they spent at least two and a half hours weekly on walking their dogs.

There is abundant data that show much diabetes, cardiovascular disease and even some cancers could be avoided altogether if only people were more physically active.

Perhaps the whole idea of Fitness with Fido would be more likely to take off if Americans understood how much their dogs need their ''walkies,'' too.

Statistics vary, but some experts say that up to 60 percent of our pooches are presently portly, almost mirroring the proportion of the people population. These dogs have many of the same health risks as overweight humans. Canine obesity is associated with heart and respiratory problems, diabetes, skeletal stress, and gastrointestinal disorders.

The biggest U.S. pet health insurance carrier, Veterinary Pet Insurance, says cardiac arrest claims for pets are up 47 percent, diabetes by 16 percent and hypertension by 27 percent. The Journal of Nutrition published a study showing that the pets of overweight owners were three times more likely to be obese than those of normal weight owners.

And while a person who has to struggle with their buttons may notice their own weight getting out of bounds, most people simply don't have the knowledge to recognize a weight problem developing in a cherished pet, so the animal gets heavier and less active, and closer to a premature death.

One long-term study by Purina showed that dogs kept to a healthy weight lived 15 percent longer than overweight dogs. That's about the same differential we see in humans.

We know that a nutrition and fitness program can turn that trend around for pets and their people, but all the tail-wagging and enthusiasm in the world won't do any good unless the people in charge - and that's us - turn the knob and step on out.

If you're the indulgent dog owner, consider that really pampering your pet means getting him healthy, right along with you. To reach the U.S. surgeon general's recommendation of 150 minutes a week of exercise, your Fitness with Fido program could start with just a 20-minute walk each day - of couse, that doesn't include stopping every 10 feet to sniff a bush.

Caroline J. Cederquist, M.D., is a family physician in Naples, Fla., who specializes in lifetime weight management. She is the author of ''Helping Your Overweight Child - A Family Guide,''(Advance Medical Press, 2002, $14.95).