Five days a week, whatever the weather, Carmen Gale hikes the woods with her high-energy German shorthaired pointer, Pico. The more miles they go, the less she weighs.

Since walking a dog became a regular part of her life six years ago, Gale figures she’s shed about 40 pounds. It isn’t all due to a dog — she’s taken up running and cycling, as well — but a dog keeps her consistent.

“When the dog’s crying and carrying on, it’s not like you get to make the decision to not go out,” said Gale, a 43-year-old aesthetician and mother of two living near Seattle.

Gale’s walking regimen with Pico may be on the more demanding side of the spectrum but she’s far from unique. Dog owners around the world long have been goaded by their pets into more exercise than they might otherwise get. And scientists have documented the effects.

So much evidence has amassed about the potential health benefits of owning pets that a committee of the American Heart Association recently decided to review the science to see what the collective research shows. Their conclusion, laid out in an article published online this month in the journal Circulation, is this:

Pet ownership, particularly dog ownership, probably is associated with a lower risk of cardiovascular disease, and may be a direct cause of lower risk.

Although this may seem obvious to many a dog-walker, Glenn Levine, MD, a cardiologist at Baylor College of Medicine and the Michael E. DeBakey Medical Center in Houston who headed the Heart Association team reviewing the studies, said the evidence is based upon statistical correlations between people who own dogs and people who don’t own dogs — not casual observations.

As Levine noted, people don’t say, “Oh, I own a dog and my blood pressure got better.” Rather, he said in an interview with the VIN News Service, “You hear anecdotal reports about how people like their pets and (the pets) enhance their quality of life, but people don’t anecdotally report that their cardiovascular health is improved.”

Improved cardiovascular health was shown in many — though not all — of the 100-plus studies reviewed by the Heart Association team.

One of the most compelling studies they cited involved 30 participants with borderline hypertension who were randomly assigned to adopt a dog from a shelter or defer adoption of a dog. Subjects in both groups had similar ambulatory resting systolic blood pressures at the outset. Two and five months after they acquired dogs, the adoption group showed significantly lower systolic blood pressure readings than the deferred-adoption group. Later, after all study participants had adopted dogs, the blood pressure of the deferred-adoption group also was lower.

The study is unpublished, but was presented at a meeting of the Society of Behavioral Medicine in 2001. Levine and team advocate that more such randomized studies be done.

In most research, associations between improved fitness and pet owning relate to walking dogs. One analysis, for example, found dog owners no less likely to be overweight than owners of other types of pets or people who had no pets. But a different analysis that distinguished between dog walkers and dog owners who didn’t walk their dogs found walkers less likely to be obese than people who didn’t walk their dogs or owned no pets.

But the benefit of pet ownership to one’s heart may relate to more than physical activity. The Heart Association team also reviewed studies examining the effects of pets on their owners’ stress levels.

In one published randomized study, 48 hypertensive patients in high-stress occupations who wished to reduce their stress agreed to acquire or not acquire a pet as part of the study. While all subjects had similar stress levels at the outset (as measured by their systolic and diastolic blood pressure, heart rate and plasma renin activity), those who adopted a pet showed “significantly diminished” stress markers six months later.

The Heart Association team also noted that while most studies assessing pets’ effects on owners’ stress levels involved dogs or cats, the calming effect has been documented as well with chimpanzees, fish, and even a goat and a snake.

“Those are small, almost anecdotal reports,” Levine said, “but we felt it was worth at least mentioning it so the article wasn’t just completely about dogs and cats.”

Despite the health evidence in favor of dogs, the Heart Association strongly cautions against acquiring a dog simply to improve one’s cardiovascular condition.

“The data were not so strong to say that people should absolutely go get a dog to increase their cardiovascular health,” Levine said, “but more importantly, we don’t want people randomly adopting a dog, neglecting the dog and sitting on the couch eating potato chips and saying, ‘Oh, I’m healthier now.’ ”

Levine added: “There’s definitely a strong feeling among members of (our) group that we did not want people to adopt a dog or some other pet where they otherwise wouldn’t, because those people weren’t likely to (give) much attention to the pet.”

Dr. Maureen Dorsey, a veterinarian in Oakland, Calif., shares that concern. Moreover, she suspects anyone who acquired a pet strictly for their health probably wouldn’t get the health benefit, anyway.

“I think it’s probably a bad idea to use animals in that utilitarian way if you don’t basically enjoy them,” Dorsey said. “Otherwise, it’s just going to be another chore. …

“Having a dog is more than putting a leash on it and talking it for a walk,” she continued. “You would have to put up with, for instance, the dog that might also crap in the house or eat one of your socks … which you know, certainly doesn’t help one’s blood pressure.

“So if you’re only getting the dog because you’ve heard this study that you’re going to walk the dog and your heart is going to get better, dream on! Because there are other aspects of owning a dog that may not be beneficial if you can’t roll with the punches.”

But people who already like dogs may well find tangible health benefits. Dorsey counts herself among them. She credits her two “beasts” with helping her to lose 15 pounds over the course of a summer two or three years ago.

“I’d gotten this young golden (retriever), and it was like, I either need to walk her 40 minutes on a forced march every day or suffer destruction in my house,” Dorsey said.

Her second dog, a 15-pound poodle mix, also needs the daily exercise, “otherwise he eats the door frames,” she added.

For people living in sketchy neighborhoods or who feel silly walking alone, dogs offer safety and legitimacy, Dorsey noted. “In my neighborhood, I would not walk around by myself without a dog,” she said. “You also feel stupid just walking by yourself.”

Gale, the dog owner near Seattle, has found that on top of the pleasure of being more fit herself, she takes pride in her pet’s fitness.

“As a woman, I don’t like to talk about my weight and my own condition, but I love talking about my dog,” she said. “There’s not one day that goes by that people don’t comment: ‘Wow, he’s a runner!’ ‘Look what good shape he’s in!’ I get so much positive feedback from having that dog.”

The truth is that she believes his good condition reflects well on her. She said, “It’s like having well-behaved kids!”