Ivory is a female bulldog that weighed 83 pounds when she first came to the Lawrence Humane Society last September. She was put on a diet and now weighs in just over 66 pounds.

It’s no secret Americans have been getting fatter — the consistent uptick in our collective weight has been documented for the past 30 years. But what might be a little less noticeable is the ever-expanding waistlines of our furry friends.

According to a February Association for Pet Obesity Prevention study, about 53 percent of cats and 55 percent of dogs were overweight. The study found this trend has been increasing year over year. Now while these numbers haven’t totally hit human standards — the CDC reports that in 2007-2008, 68 percent of Americans were overweight or obese — it is a cause for concern that so many of our pets are overweight or obese.

Cats, dogs, gerbils, hamsters — all of them can come down with health problems similar to humans because of extra girth. And, for the most part, they have only their loving owners to blame for their condition.

“They can’t open the fridge — well, I guess some dogs could do that — but for the most part they are completely dependent on you for food. You are their refrigerator,” says Matthew Coles of the Animal Hospital of Lawrence, 701 S. Mich., who admits it’s hard to say no to one’s beloved pet. “So, if they are overweight, there’s only one person that could be in charge or the reason for that. And that’s because they’re getting fed too much.”

But it’s exactly because we control many of the factors that can lead to chubby fluffies and fidos that we can also control many of the factors that can lead to sustained weight loss. Coles and Robin Michael of Clinton Parkway Animal Hospital, 4340 Clinton Parkway, share how to slim down your pet.

Know what you’re dealing with. Start by weighing your pet regularly — whether he or she is overweight currently or not. It may seem a little silly to keep a chart documenting your pet’s weight, but it’s a more accurate predictor than your eye. By the time you notice your pal is looking chubby, you’ll have a lot of poundage to undo. Also, remember that on a 10-pound cat, a gain of even half a pound can mean more strain on the body. Michael says another easy marker is picking up your animal and making sure you can feel the ribs.

Ditch the buffet. First things first when controlling your pet’s weight — get rid of trough-style feeding. Our experts say that rationing the amount of food is much more important than changing the type of food you feed your animal. Check the bag and pick a set amount, and feed the animal at regular intervals — breakfast, lunch and dinner, or just breakfast and dinner — rather than just keeping food out all the time for the animal to eat at will. Coles also says that you may need to feed even more than three times a day at first, especially with cats, who will might harangue you for food until they are fed. Just do what your schedule allows.

But keep the routine. Do you give your dog a biscuit every day when he or she goes into a kennel? Or do you practice tricks? You can still stick to your normal routine, just break the treat into several pieces.

Exercise. It goes without saying, but adding an extra walk or playing more often with a dog can burn calories and help him or her lose weight. With cats, you can try playing, says Coles, but it’s a bit harder to control.

Consider a diet change. If your animal is already on a set amount of food daily and can’t get a lot of exercise for one reason or another, look at switching to a lighter food. Michael says that for cat owners, this can be especially important because it’s hard to exercise a cat. Luckily, she says, wet cat food is much lower in calories than dry, thus making it easier to decrease calories for a period of time.

If the diet changes, separate. Michael says that if you do decide to change an animal’s diet, but have one or more other animals who will remain on the previous meal plan, make sure and separate them out and meal times. She says she has a diabetic cat on a special diet and sets that cat apart from her other two felines during mealtimes to make sure everybody is getting the right nourishment.

Don’t forget medical tests. If you make the above changes and your pet still isn’t losing weight, contact your vet. Both Michael and Coles say that your pet could be suffering from a thyroid imbalance or other ailment.