Heavyweights of the four-legged kind

There are a lot of fat cats out there, not to mention dumpy dogs, according to the results of a recent national study.

The study by the Association for Pet Obesity Prevention, using data from 95 veterinary organizations, found that about 44 percent of dogs and 57 percent of cats in the United States are overweight or obese.

Although lack of exercise is a contributing factor, poor diet is the primary cause of weight issues in pets, veterinarians say.

"A lot of times, the problem is between the ears of the owners, not the pet," said Chris Keller, owner of the Mountain Hospital for Animals on Lookout Mountain, Tenn. "All of those bad habits that have developed over time are associated with owners that have intensified the animal's interest in eating what they're eating."

Owners have "total control" over what their pets eat, said Candace Hadden, a veterinarian at the Animal Medical Center of Fort Oglethorpe.

"It's not like they sneak out and go buy a Big Mac," she said. "It's still such a problem to get owners to say 'no.'"

Just as with humans, being overweight can cause a variety of health problems in pets, including arthritis, breathing difficulty, heart disease and diabetes, Dr. Hadden said.

But reducing a pet's weight has more than just cosmetic benefits. Animals kept at their ideal weight are more likely to live longer, according to a 2002 study by Nestlé Purina PetCare.

The Purina Life Plan Study, which kept tabs on a group of 48 Labrador retrievers for 14 years, found that reducing their daily calorie intake by 25 percent extended median lifespan by 15 percent or about two years.

Lookout Mountain resident Susu Brock said she's concerned about how extra pounds may be affecting the health of her 13-year-old Jack Russell terrier/beagle mix, Mae Mae.

"I am concerned about her weight, especially because of her age," Ms. Brock said. "I worry about her heart, mostly, carrying all that weight around. She sleeps a lot. Part of it is age, and I think part of it is weight. I'm cutting her portions back."

Before adjusting a pet's diet, it's important to understand their nutritional needs, veterinarians said.

Feeding a dog meat from the dinner table may seem like an appropriately protein-rich snack for a carnivore, but just like humans, pets' nutritional requirements are complex, Dr. Keller said.

"Even though dogs and cats have lived around humans for centuries and centuries, there are still specific things that make them very different from humans, as far as what their diet needs to be," he said.

Cats, for example, need a certain amount of grass in their diet to help with furballs and intestinal health, and dogs, contrary to popular belief, are omnivores, not carnivores, Dr. Keller said.

Part of pets' weight problems are the result of owners' use of food as a reward, said Ernie Ward, founder of the Association for Pet Obesity Prevention.

Feeding treats to pets assuages the guilt of being too busy to spend time with the animals, but it causes more harm than good, Dr. Ward said.

"If you have a fight with your girlfriend, you give her a box of chocolates and flowers," Dr. Ward said. "We apply the same psychology to our pets."

The high percentage of fat, sodium and sugar makes some pet treats not only "calorie grenades" but potentially habit forming, Dr. Ward said.

"This is why I call this food, especially the treats, 'kibble crack,' because it's that addictive," he said. "We've changed their brain chemistry by conditioning this response."

Table scraps are another obesity culprit, said Lisa Peterson, a spokesperson for the American Kennel Club. Not only is there a danger in feeding human dinnertime leftovers such as cooked onions and turkey fat to dogs, such food doesn't fulfill the animals' nutritional needs, Ms. Peterson said.

"Some of these things, in large enough doses, depending on the dog's body weight, can cause a lot of problems, including death," she said. "My rule of thumb with dogs is to always feed them dog food."

For some pet owners, adjusting their own activity level and diet can benefit their pet as well, veterinarians said.

Dr. Ward, who is also a certified personal trainer, said some owners need the extra-mile walk just as much as their dog.

"There's an old saying that, 'If you have a fat dog, you need to get out more,'" he said. "Basically, you can look at your dog and know that you two are not walking him enough, so maybe you both need to get out and exercise."