(LifeWire) -- The growing obesity problem doesn't exclude pets.
Fat Charlie lived up to his name, weighing 168 pounds before he was put on a diet.
"We are seeing so many overweight dogs and cats, and it's sad because their weight levels are completely manageable with diet changes," says Dr. Kristine Yee, a veterinarian at California Animal Hospital in Los Angeles.
But pet owners are often slow to admit that their animals need to shed pounds.
A 2005 study from pet-food maker Purina found that 60 percent of pets in the U.S. were overweight.
But almost half of the owners of overweight pets rated their cats and dogs as having the "ideal" body condition.
Pet obesity can be a sensitive issue, says Susan Davis, a pet nutritionist based in Lake Forest, California, who has helped many pets trim down. Because some owners treat their pets like their children, people can take it personally when you tell them they have an overweight animal.
But pet obesity isn't just about looks. Extra weight can lead to myriad health problems and even shorten an animal's life span.
"Some of the pets I've seen have severe respiratory, cardiac, metabolic and orthopedic dysfunction that is drastically worsened by just being obese," Yee says. One beagle she treated tore a cruciate (knee) ligament three times and had to have multiple surgeries, all because he was carrying too many pounds.
Why so fat?
It's common for people to show their pets love by giving them a lot of food and snacks. They pour on the treats, not realizing that one dog biscuit can be 100 calories. They let cats and dogs feast on the fat of their rib-eye steaks and other scraps from the dinner table.
"A lot of owners think their pets are suffering if they aren't getting table scraps and treats," Yee says. "But dogs don't need people food; they're perfectly happy with their own food."
As with humans, excessive portions are a main cause of the weight problem.
"People don't use measuring tools most of the time," says Davis, a certified clinical nutritionist. "They wing it or free-feed their pet, and end up giving them three cups instead of the recommended one-cup serving."
Like people, pets need to stay active, too. This means walking your dog or cat regularly and playing with them, indoors and out.
The obesity test
You can find out if your pet is overweight by determining its body condition score. This test is available on several Web sites, including Ohio State University's College of Veterinary Medicine. It's the same test that many vets use to determine a pet's ideal weight.
Yee offers two simple tests that show obesity:
• Run your hands across the chest of the dog or cat. You should always be able to feel their ribs but not see them. There should never be a layer of fat over the ribs.
• Look at the standing dog or cat from a bird's eye view. They should have what looks like a waist that tucks in right in front of the hips.
Steps to slimming down
Davis gives these tips to get pets back into shape:
• Control portions. Look at everything you are feeding your pet -- pet food, treats and human food -- and reduce the amount. Use proper measuring tools.
Also, food packages will recommend portions by weight ranges. Use the weight range of the overweight pet's ideal weight, not its current weight. And use the lowest suggested amount for that range. For example, if the manufacturer recommends two to three cups for dogs over 30 pounds, give the dog two cups.
• Control quality. Don't feed your pet human junk food like pizza or sweets such as baked goods, ice cream or cookies. Home-prepared meals using fresh ingredients are acceptable, Davis says. Wholesome items such as brown rice, fresh lean meats and carrots are recommended. Be sure to avoid the human foods that can be toxic to cats and dogs: grapes/raisins, mushrooms, chocolate and coffee. Tomatoes and garlic can also be toxic for cats.
• Increase exercise. Get into the habit of walking your dog every day. Getting outdoors is good for a pet's emotional health, too, giving it a chance to make social contact and find out what is going on in the neighborhood.
With dogs, you can also play fetch, play hide and seek, set up obstacle courses for them or take them swimming. Cats can stay active indoors or out by playing with toys, "hunting" for food, or being walked outside on a leash.
Diet pet foods are also available. Ask your vet if he or she recommends feeding your pet reduced-calorie foods. Homemade meals tend to be lower in calories and healthier than prepared pet foods, because they don't contain fillers. In either case, vets say, portion control is the main issue in reducing or managing an animal's weight. E-mail to a friend
LifeWire provides original and syndicated lifestyle content to Web publishers. Joan Shim is a freelance writer and former editor at Pet Product News.