Kibble Confusion

In a nation of tubby tabbies and plump pooches, Tufts experts give the scoop on good nutrition for our pets

illustration of overindulged pooch

When the eight-month-old puppy arrived at the Cummings School, he wasn’t bouncing around the waiting room like most healthy pups do. The dog was limping and began having seizures. Working with surgeons and critical care specialists, Dana Hutchinson, a resident in veterinary clinical nutrition, also discovered the pooch had low bone density.

Intending to feed the pup a healthy diet to help control episodes of diarrhea, the dog’s devoted owner had been giving him home-cooked meals of hamburger and rice, broccoli, eggshells and vitamin supplements. But the diet, like most homemade ones, wasn’t balanced, and the dog had become severely calcium deficient, probably getting 25 percent of what a growing pooch needs. The diet also lacked myriad other nutrients.

“The owner had no idea. She thought she was doing the right thing,” says Hutchinson.

If we’re confused about our own nutrition—and the stunning array of foods, supplements, nutrition books and websites suggests that we are—we’re even more uncertain about what to feed our canine and feline companions. The obesity epidemic that is affecting human health has spread to our pets, which, like many of us, are eating more and exercising less. And as Americans increasingly choose local, organic and unprocessed foods for their own tables, some animal owners have become wary of mass-produced pet foods and are looking for other options.

So what’s a conscientious pet owner to do? Veterinarians working in a relatively new specialty, veterinary clinical nutrition, are helping provide owners and other clinicians with science-based advice about diets that will keep their pets healthy and fit. The Nutrition Service at Tufts’ Foster Hospital for Small Animals, led by Lisa Freeman, a Tufts-educated veterinarian with a Ph.D. from the Friedman School of Nutrition Science and Policy at Tufts, and the residents she has trained have done some groundbreaking work on the role of nutrition in preventing and treating disease in animals.

Nutritionists in veterinary medicine once focused almost exclusively on what to feed production animals to get the most milk out of a cow or the most meat from a pig. Today they’re more like human nutritionists, determining the optimal caloric and nutritional requirements for specific breeds of cats and dogs at all stages of life. They’re also using nutrition to treat a range of chronic conditions, including heart and kidney disease, cancer and obesity.

Battle of the Bulge

Your cat never has to fit into a pair of designer jeans, but that doesn’t mean you don’t have to count his calories. Obesity carries many of the same health risks for companion animals as it does for humans: diabetes, arthritis and potentially, a shortened lifespan. Research in the United States and the United Kingdom puts 25 to 40 percent of middle-aged cats and dogs in the overweight or obese category.

Some scientists say the rate is even higher: a recent Cummings School study found that 70 percent of otherwise healthy cats were overweight or obese. Considering these statistics, it’s pretty likely your animal is overweight or obese.

Don’t think so? That might be part of the problem. Veterinary nutritionists suspect that in wealthier countries like the United States, we may have forgotten what a healthy animal should look like. A body condition scale—an illustrated guide that places cats and dogs on a spectrum of one to nine, from “emaciated” at one end to “grossly obese” at the other—is one method for assessing your pet’s body condition.

However, Freeman says, there’s an even easier weight reality check. Hold your hand out, palm up. Feel your palm just below your fingers. If that feels something like the side of your dog or cat, your pet needs to shed some pounds. Now flip your hand over and make a fist. Run your other hand along your knuckles. A dog or cat whose ribs feel like that is too thin. Finally, hold out your open hand, palm down, and feel those knuckles again. That’s what a fit pet feels like. If you’re not sure how your pet measures up, consult your veterinarian.

Our dogs and cats don’t go to restaurants or make impulse junk-food purchases at the supermarket, so how did they get so pudgy?

Like us, animals today expend less energy than their ancestors did, and they’re spending more time indoors, with ready access to food. But some of the reasons our pets are plump are unique to them.

“We’ve really gotten good in veterinary medicine at advocating neutering,” says Kathryn E. Michel, V83, an associate professor of nutrition at the University of Pennsylvania School of Veterinary Medicine. “But neutering does increase the risk of weight gain.”

And thanks to the pet food industry’s extensive taste tests, dog and cat food is yummier than ever, prompting pets to keep nibbling kibble even after their hunger is satiated. “Ten years ago, dogs used to stop eating when they were full,” says Freeman, J86, V91, N96. “Now dog food tastes really good, so pets often continue eating even after they’re full.”

For a more insidious reason behind pet obesity, take a look at pet treats, “the fastest-growing segment of the pet food industry,” says Hutchinson. Shaped like bones or fire hydrants, fish or mice, pet treats appeal to the human shopper, but can pack a caloric punch many owners don’t even realize.

“Often, people are feeding their pets the right amount of food [at mealtime], but the pets are just getting too many extras,” says Michel.

Given that a cat or a small 10-pound dog needs as few as 250 calories a day, even a couple of extra treats can pack on pounds. “A treat may seem small to us,” says Freeman, “but if you think about the calories, it might be a big percentage [of a pet’s daily caloric requirement]. It might be like us eating a Big Mac.”

Dog biscuits range from 5 to more than 300 calories, and some “dental bones” contain more than 1,000 calories. Even rawhide strips can have a hefty number of calories. A general rule is that owners should aim for treats to comprise 10 percent or less of a pet’s daily caloric intake. For a small dog or cat, that means limiting treats (and table food) to less than 25 calories each day.

In theory, it should be easy for owners to restrict their pets’ calories and encourage more activity. In practice, however, it can be just as difficult for pets to shed weight as it can be for the people who own them. More often than not, it’s the humans who need to change their ways.

“More and more pets are viewed as members of the family, so when you have that orientation, you are predisposed to indulge the pet,” says Michel. On top of that, owners tend to misinterpret their pets’ behavior around treats, especially dogs, which can appear incredibly ravenous at mealtime. “Pets beg, regardless of being hungry,” says Debbie Linder, V09, a resident in veterinary clinical nutrition at the Cummings School. “They develop patterns, and they train us.”

With a little sleuthing, a veterinary nutritionist can help pet owners break bad habits—like doling out too many treats or leaving out too much food. For pets that still don’t drop the weight, the Cummings Nutrition Service offers consultation on site, or via phone or email, to develop more effective dietary plans and then monitor an animal’s weight.

That’s especially important for cats, which can wind up with a serious liver problem if they lose too much too fast, notes Freeman. “If the cat or dog hasn’t lost weight, we have to make adjustments and keep making adjustments until it works.”

The owner education component is essential for reversing the obesity trend and maintaining a healthy animal. “Pet owners are more interested in nutrition now, yet often their vet may not be able to answer their questions because they didn’t receive the training in school,” says Freeman, who is one of about 70 veterinarians in the country to earn board certification in nutrition. Less than half of the 28 U.S. veterinary schools have a nutritionist on the faculty. Come January, the Cummings School will have two teaching students, conducting research and advising pet owners.

Fit for Life

So how do you get your cat off the couch? One strategy for blending exercise with portion control is to put your pet’s entire meal inside a treat ball, or hide portions of his meal all over the house. For very food-motivated animals, try opening a can of wet food, then walking up and down a flight of stairs and having your pet follow you. Take your dog for an extra walk around the block or trick your cat into getting exercise with toys like lasers and feathers.

But don’t rely too much on exercise to trim the tabby down. “It’s important to realize that if a cat needs to lose weight, you’re not going to get that loss just from exercise,” says Hutchinson. “Exercise is great. It helps increase lean body mass. But to actually lose weight, you have to restrict calories.”

One of the toughest things about getting your pet into shape is figuring out your animal’s daily nutritional and caloric requirements. All pet food labels have to contain feeding directions, but some are more accurate than others, Freeman says. Feeding directions are just a starting point. The real test is what your pet looks like. If you can easily feel the ribs, without pushing hard, then you’re feeding the right amount. If you have to push hard to feel the ribs—or you can’t feel them at all—you’re feeding too much, Freeman says.

Some, but not all, pet food manufacturers list the calories on the package, although that’s only required for foods labeled as “light,” “low calorie” or “reduced calorie,” says Freeman. If your brand doesn’t list the calories, look for that information on the company’s website or by calling or writing the manufacturer.

Even foods labeled as light or marketed for weight control can vary tremendously in calories. “You may buy a pet food that is marketed as a weight-loss diet, and it may have twice as many calories [as another brand],” says Linder.

In a study published in the January 1, 2010, issue of the Journal of the American Veterinary Medical Association, Freeman and Linder examined 93 commercial dog and cat foods marketed as weight-management diets. They found that dry dog foods ranged from 217 to 440 calories per cup and also varied wildly in price—from 4 cents to more than $1.10 per 100 calories. The study also concluded that “the vast majority of foods’ directions would result in no weight loss or even weight gain,” says Freeman.

Deciphering the Label

Whether your pet is overweight or in perfect shape, there are several things to consider in selecting the best food for your animal.

Pet foods are regulated by the Food and Drug Administration, the U.S. Department of Agriculture and the individual state departments of agriculture. But it is the Association of American Feed Control Officials (AAFCO) that provides guidelines for the manufacture, labeling and sale of pet foods, with the goal of ensuring safe and nutritious diets. The AAFCO also sets standards for the levels of nutrients that should be in dog and cat foods for the different stages of life, from puppies and kittens through old age.

Veterinary nutritionists generally agree that owners should look for foods that are tested using AAFCO feeding trials—rather than by formulation—to meet the minimum AAFCO levels. You can tell how the food was tested, Freeman says, by looking for the nutritional adequacy statement that is required on all pet food labels. “This is the most useful piece of information on the label,” Freeman says, because it provides answers to three critical questions:

• Is the food complete and balanced?

• For which stage of a pet’s life is the food intended?

• How are the claims on the label substantiated?

Pet foods, Freeman says, are designed to meet the minimums for one of the recognized life stages: growth and reproduction or adult maintenance. Owners should be aware that the life stage a food is marketed for may not necessarily be the same stage for which the food actually meets the minimums, she says.

For example, many diets marketed for adult cats actually meet the requirements for all stages of life, meaning their nutrient levels are high enough for kittens or lactating queens. By checking the nutritional adequacy statement on the label, you can select the food that is most appropriate for your pet’s stage of life.

A pet food intended as a complete and balanced diet must be substantiated in one of two ways: by formulation to meet the levels established by the AAFCO or through feeding trials. Feeding trials, Freeman says, provide better assurance that the food meets your pet’s nutritional requirements.

When feeding trials have been done, the label should read: “Animal feeding tests using AAFCO procedures substantiate that Brand X provides complete and balanced nutrition for growth (or maintenance).” If the food is only formulated to meet requirements, the label has to say: “Brand Y is formulated to meet the nutritional levels established by the AAFCO Dog (or Cat) Food Nutrient Profiles …”

Other information on pet food labels is more about advertising than nutrition, Freeman says. While there are guidelines governing the use of the word “natural,” meaning the food does not contain chemically synthesized ingredients, descriptive language such as “holistic,” “organic,” “gourmet” and “human grade” are primarily marketing terms, she says.

Yet another reason for pet owners’ heightened interest in what their pets eat may be a result of the pet food recalls of 2007, when several major companies issued voluntary recalls for hundreds of brands. Something in the food was causing kidney failure in otherwise healthy animals, primarily cats.

Investigators from the veterinary school at Cornell University, New York State and the U.S. Food and Drug Administration found that the food contained the toxic industrial resin melamine, the same substance that killed six and sickened 300,000 children in China in 2008, after they drank milk tainted with it.

In the case of the poisoned pet food, a Chinese supplier had intentionally and illegally spiked wheat gluten, a protein used in most commercial pet foods, to boost its apparent protein content. The recalls prompted many pet owners to rethink what they were feeding their animals.

Some started buying foods made by smaller companies with more familiar-sounding ingredients. But those brands may not be all they claim, says Michel. “Often alternative pet foods are made by commercial manufacturers and just marketed as alternative,” she notes.

Other pet owners turned to preparing homemade meals for their animals. It can be done, Freeman says, but owners should consult a veterinary nutritionist before deciding to cook for their pets.

“Unless they’ve been formulated by a veterinary nutritionist,” Freeman says, “almost all of the homemade diets I see owners feeding are very nutritionally unbalanced.”

Even a tiny change “can easily make a balanced diet unbalanced,” says Hutchinson, noting that “just substituting white for brown rice can completely alter the diet.”

And while human nutritionists extol the virtues of fresh foods and home-cooked meals to avoid the high salt and fat content in processed foods, when it comes to your pet, “it’s not better to cook for them,” Freeman says. “It can be done, but in many ways it’s probably less desirable. People are often surprised to hear that. They say, ‘In that case, I’d rather open a can.’ ”


This story first appeared in the Winter 2010 Tufts Veterinary Medicine magazine.

Jacqueline Mitchell can be reached at


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