Obesity is a prime example of a medical condition that affects a variety of species, especially when the species share similar habits and environments. According to the Centers for Disease Control and Prevention, over 71 percent of Americans over the age of 20 are overweight or obese. And according to the Association for Pet Obesity Prevention, 56 percent of dogs and 60 percent of cats are overweight or obese. Obesity is also increasing in horses.

Obesity in both people and animals is complex and involves multiple factors, including genetic and environmental risk factors, diet, level of physical activity, stress level, and other lifestyle behaviors. But the basic cause is the same across species: there’s an energy imbalance where too many calories are consumed or too few calories are burned. More people and their pets are living a less physically active lifestyle but still eating an energy-rich diet.

Obesity goes a lot further than skin deep. It’s a major health hazard for all creatures, increasing the risk for several potentially serious health problems. Disorders linked to obesity in pets include:

• Orthopedic problems, such as osteoarthritis, torn or ruptured cruciate ligaments in the knees, and slipped disks in the back;
• Laminitis in horses, also called founder (a painful cause of lameness in which the delicate tissues that connect the small bone within a horse’s hoof to the inside of the hoof wall become inflamed and damaged);
• Breathing problems;
• Urinary and reproductive disorders;
• Some types of cancer;
• Type 2 diabetes in cats;
• Fatty liver disease in cats and horses;
• A decreased ability to handle heat;
• Increased risk of having anesthetic and surgical complications; and
• A shortened lifespan.

Overweight and obese pets lose out, both in terms of health-related quality of life and life expectancy.

In 2013, the American Medical Association officially recognized obesity as a disease in people that requires medical attention. And although obesity is the most common nutritional disorder of dogs and cats in Western countries, the veterinary profession has been slow to formally call it a disease. That may change soon, however, as there’s a growing push to follow “our human counterparts’ move” and recognize pet obesity as a disease, said Dr. Ward, the founder of the Association for Pet Obesity Prevention.

Significant parallels exist between people and animals regarding the causes of obesity, its associated complications, and how to prevent and manage obesity in patients. Preventing obesity—through a balanced diet and regular exercise—should be a priority in both human and veterinary medicine.

Managing obesity in both people and pets involves a healthy diet, calorie restriction, and regular exercise. Sometimes, weight loss drugs are prescribed. FDA has approved several weight loss drugs for people, and one drug, Slentrol (dirlotapide), is FDA-approved to manage obesity in dogs.

The biggest hurdle for both pets and people isn’t the initial weight loss; the real challenge is maintaining the lower body weight by sustained long-term lifestyle changes. For owners who are also overweight or obese, the human-animal bond can motivate them to stick to a healthy lifestyle. There is great value in people and pets exercising together. For example, people who have a dog are more likely to get exercise from walking, which in turn may help prevent a number of obesity-related disorders in both the owner and the dog. The benefits are clearly mutual!

Helping pet owners develop a healthy lifestyle for themselves and their four-legged companions is at the heart of a One Health approach to obesity.

This is a true story; only the name and coat color have been changed to protect the innocent.

Rosie was a sweet girl; a happy black Labrador retriever, who, like many labs, lived to eat. Food on the kitchen counter? Kiss it goodbye. Counter-surfing was a rewarding daily sport in Rosie’s house. Unopened loaves of fresh bread were a favorite target—a tasty mid-day snack, plastic bag and all.

When Rosie damaged both her knees at a young age, she began to have difficulty moving around, especially after arthritis set in. Her owner, feeling badly for Rosie and knowing that eating was Rosie’s greatest joy in life, fed her more than an inactive, arthritic, young dog needed. Cutting back the amount of food she fed Rosie was, emotionally, not an option.

As time went on, Rosie gained weight. And she gained more weight. Rosie became a 75-pound lab trapped in a 150-pound body; she could hardly walk. Getting up after laying down was hard work—she had to prop herself up with her front legs and slowly inch her way into a standing position. A simple change in position was difficult; walking occurred only when necessary. So, at 8 years old—middle-age by Labrador retriever standards—Rosie died of liver disease caused by her obesity.

Obesity is a common topic these days, whether in newspapers, online, or on TV. More than one-third of American adults (42.4%) are obese. According to the Centers for Disease Control and Prevention, 21.2% percent of U.S. children and adolescents are obese. But what, exactly, is obesity?

Obesity is a term simply meaning a buildup of fat in the body. Although people may think of fat as relatively harmless or somewhat inconvenient, it is anything but. The fat in a person’s body, like the fat in an animal’s body, is made up of many tiny cells. These cells make various hormones, like insulin, and secrete these hormones directly into the bloodstream. (Hormones are special chemicals that regulate certain cells or organs in the body.)

In a person or an animal with low body fat, the amount of additional hormones produced by fat cells is small because there aren’t many fat cells. However, in people or animals with higher body fat and more fat cells, a greater amount of additional hormones is secreted into the bloodstream, negatively affecting the body. Obesity leads to a variety of diseases including: Type 2 diabetes mellitus, high blood pressure, gallstones, fatty liver disease, sleep apnea, heart failure, degenerative joint disease, asthma, and cancer.

Just as obesity has become a serious problem in people, it is also a growing problem in their pets. According to the Association for Pet Obesity Prevention, 59.5% of dogs and 55.8% of cats in the U.S. are overweight or obese. The diseases seen in these pets are eerily similar to those reported for people: Type 2 diabetes mellitus, osteoarthritis, high blood pressure, heart and respiratory disease, kidney disease, inflammation, and shortened life span.

Obesity is a complex disease in people. Genetics, environmental factors, other diseases, and medications all may play a role. It’s a similar story in pets. There are pet-specific factors, such as if the pet is on any medications or has a disease that contributes to obesity; environmental factors, such as not enough exercise and how the pet is fed by the owner; and genetics, with some breeds more prone to being overweight. Studies show that weight loss in pets improves their overall health by:

• Improving respiratory function,
• Decreasing osteoarthritis in shoulder, hip, and elbow joints,
• Lengthening the median life span in dogs, and
• Delaying the onset of chronic diseases in dogs.

Your 8-year-old chocolate lab is putting on weight, and you know she should probably lose a pound or two. But when she looks at you pleadingly with those big brown eyes, how can you resist handing out just one more treat?

It’s not easy. But it may be important.

“Just as obesity has become a serious problem in people, it’s also a growing problem in pets, one that can seriously harm your pet’s health,” says Carmela Stamper, a veterinarian in the Center for Veterinary Medicine (CVM) at the U.S. Food and Drug Administration. Among CVM’s responsibilities are making sure that food for animals—which includes animal feed, pet food, and pet treats—is properly labeled with truthful claims, and is safe for animals and the people who handle it.

According to a 2018 survey by the Association for Pet Obesity Prevention, an estimated 59.5% of cats and 55.8% of dogs in the U.S. are overweight.

“The diseases we see in our overweight pets are strikingly similar to those seen in overweight people,” Stamper says, naming as examples diabetes mellitus (also known as Type 2 Diabetes, in which the body does not use insulin properly), osteoarthritis, high blood pressure, heart and respiratory disease, and kidney disease.

“We want our pets to live happy lives, but we also want them to live long ones,” Stamper says. Obesity in your pet causes chronic inflammation throughout the animal's body, and it can significantly shorten the animal’s life span.

How Fat is Too Fat?

According to the Association for Pet Obesity Prevention, pets that are 10-20% over their ideal body weight are considered overweight, while pets 20% and over are considered obese. But the ideal weight is relative, depending on the animal’s breed, age, body type, and metabolism.

“In dogs, some breeds seem more inclined toward obesity than others,” Stamper notes. Labs and beagles are two examples, as well as long, low dogs such as dachshunds and basset hounds. In contrast, while veterinarians are reporting more overweight and obese felines, no one specific cat breed is prone to obesity.

Neutering can slow down a dog or cat’s metabolism, and so can aging, especially if the animal gets less exercise than when younger. It is important to talk to your veterinarian about how much food your dog or cat should be eating.

Keeping Track: Important Questions to Ask Your Vet

The real expert on the ideal weight for your animal is your vet, who marks changes over time in a way that you—who sees your animal every day—may not.

How does your vet know if a pet’s weight has edged past normal and become unhealthy? Many use body condition scoring systems for both dogs and cats, such as a 1-95 point scale (with a “1” being very skinny, and a “95” being obese.) Where on the scale does your animal fall?

“Ask your vet to explain the scoring system he or she uses,” Stamper says. And ask for specifics about what to look for, such as:

• What are some specific signs that my animal is gaining weight?
• What is a good normal weight for my pet?
• What type of food do you recommend, and how much is a serving? How many times a day should I feed my pet? (Stamper notes that the amount recommended on the side of the food bag may not be right for your particular animal, depending on your pet’s age, activity level, or other factors).
• Does my pet have a health condition (such as arthritis) that makes it advisable to keep weight on the low side?

“There’s a good reason why your animals get weighed at every vet visit,” Stamper says. Pet owners should make it a habit to ask how their animal is doing weight-wise and whether there is cause for concern if their animal is significantly overweight—or underweight.

Being too skinny or weight loss can be the sign of a health problem, too, Stamper adds. In particular, a dog or cat who normally enjoys eating but suddenly shows a lack of appetite can be exhibiting a symptom of a serious health problem that may warrant a visit to the vet to be sure everything’s okay.

Signs to Look For

In the meantime, there are some basic signs to look for to determine whether or not your pet is at a healthy weight.

• Look at your animal from above. Does your pet have a definite waist? “If not, and her back is broad and flat like a footstool, she is likely overweight,” Stamper says.
• Run your hands along your animal’s side. Can you easily feel the ribs, or do you have to push hard to feel them? Are they too prominent?
• Does your animal have a “tucked” abdomen, or a sagging stomach? If you can easily grab a handful of fat, that’s a sign your animal is overweight.

All things in moderation, Stamper says. For most animals, the occasional treat is just fine.

“It’s not unusual for people who are very focused on their own weight to be overly focused on their animals’,” she adds. “The key is to talk to your vet if you’re concerned.”

Like most pet owners, you likely know it’s better to feed your dog or cat pet food rather than table scraps. While an occasional treat of “people food,” like a piece of bacon or a bite of hamburger may be fine, eating too many table scraps may cause your pet to have an unbalanced diet. You can determine if a pet food meets your pet’s nutritional needs by looking at the nutritional adequacy statement on the label. If this statement includes the phrase “complete and balanced,” then the product is intended to be fed as a pet’s sole diet and should be nutritionally balanced. Treats, snacks, and supplements are typically not intended to be a pet’s sole diet, so these products are often not complete and balanced.

To have "complete and balanced" in the nutritional adequacy statement, a dog or cat food must either:

• Meet one of the Dog or Cat Food Nutrient Profiles established by the Association of American Feed Control Officials (AAFCO); or
• Pass a feeding trial using AAFCO procedures.

For a product to meet one of the AAFCO nutrient profiles, it must contain every nutrient listed in the profile at the recommended level.

The association established the first Dog Food Nutrient Profiles in 1991, and shortly after, in 1992, the first Cat Food Nutrient Profiles. Since then, AAFCO has updated the nutrient profiles for both species when new nutritional information has become available, most recently in 2016. The profiles incorporate the most current information on good nutrition for dogs and cats and provide practical information for pet food manufacturers.

All the nutrients listed in each profile have a minimum level, and some also have a maximum level. Because not all life stages are the same in terms of nutritional needs, AAFCO established two nutrient profiles for both dogs and cats—one for growth and reproduction (which includes growing, pregnant, and nursing animals) and one for adult maintenance. A growing kitten or a dog nursing six pups, for example, has different nutritional requirements than an older, spayed or neutered pet. Pet food made for adult dogs and cats contains lower levels of some nutrients, eliminating unnecessary excesses.

When you see a reference to either an AAFCO nutrient profile or a feeding trial using AAFCO procedures on a pet food label, you’re better assured that the "complete and balanced" claim is valid. Endorsements and seals of approval from other organizations are not assurances of nutritional adequacy and may be misleading.

AAFCO publishes the nutrient profiles for dogs and cats in the association’s annual Official Publication.

Comparing Pet Food Products

The AAFCO Dog and Cat Food Nutrient Profiles express nutrient levels on a "dry matter," or moisture-free, basis. But, the guaranteed analysis on a pet food label expresses nutrient levels on an "as-fed," or moisture-included, basis.

Canned pet food is typically 75 to 78 percent moisture, whereas dry pet food is typically 10 to 12 percent moisture. You can directly compare nutrient levels between products with near-equal moisture content. However, if you want to compare nutrient levels between products that differ widely in moisture content—say between canned and dry—you must first convert the levels in the guaranteed analysis from an as-fed to a dry matter basis so that you’re comparing at near-equal moisture content.

To do this conversion, divide the percent guarantee for the nutrient (listed in the guaranteed analysis on the label) by the percent dry matter of the product and then multiply by 100. To get the percent dry matter of the product, subtract the percent moisture guarantee (listed in the guaranteed analysis on the label) from 100.

An Example
Your cat is healthy with a normal appetite. You want to compare the crude protein level in two cans and one bag of adult cat food. The AAFCO Cat Food Nutrient Profile for adult cat maintenance sets the minimum level of crude protein at 26 percent on a dry matter basis. But remember, the guaranteed analysis on each product’s label expresses the minimum crude protein level on an as-fed (moisture-included) basis. You must convert this to a dry matter basis to make a meaningful comparison.

If you simply looked at the crude protein level listed in the guaranteed analysis on the products’ labels without converting to a dry matter basis or taking into account each product’s moisture content, you would mistakenly think the dry food has the highest level of protein. In actuality, it has the lowest protein level when you compare the products at near-equal moisture content. All three products contain more than 26 percent protein on a dry matter basis, so they all meet AAFCO’s minimum level for crude protein in adult cat food.

Note that if you want to compare only the two canned food products, you don’t need to do the conversion calculations because the products have the same moisture content (the same moisture guarantee). You can just look at the crude protein level listed in the guaranteed analysis on each product’s label and see that Canned Food #2 contains slightly less protein.

The U.S. Department of Agriculture (USDA) and the Department of Health and Human Services jointly created the Dietary Guidelines for Americansto address proper nutrition and the prevention of diet-related diseases in people. The nutrition and health experts in both departments re-evaluate current science and medical knowledge every 5 years and use that information to revise the guidelines when necessary.

Until 2010, the guidelines provided nutrition advice for healthy Americans over the age of 2 years. The latest revision, released in 2020, addresses this healthy population and those Americans at an increased risk of obesity-related diseases. The guidelines provide recommendations on how to eat healthy and maintain proper calorie balance (calories in equal calories out) to prevent becoming overweight or obese. An easy–to–understand picture, the USDA Food Plate, is a companion to the guidelines and gives people a visual example of proper food portions on their dinner plates.

Unfortunately, similar dietary guidelines don’t exist for pets. In 2010, the American Animal Hospital Association (AAHA) released a document written for veterinarians and their staff, entitled AAHA Nutritional Assessment Guidelines for Dogs and Cats. The association drafted the document because “good nutrition enhances pets’ quality and quantity of life, and is integral to optimal animal care.” The guidelines give veterinarians and their staff a no-cost, quick way to obtain crucial nutrition information for pets. Using this information, veterinarians are better able to help pet owners make better decisions about their pets’ nutrition and overall health.

The nutritional assessment provides veterinarians and their staff with:

• An increased awareness of the importance of nutritional assessments in dogs and cats,
• A set of guidelines to help evaluate the nutritional health of dogs and cats, and
• More evidence and better tools to support recommendations about nutrition to pet owners.

According to the AAHA guidelines, a screening nutritional assessment should be performed on every dog and cat as part of a routine physical examination. Based on the assessment, the veterinarian, with the pet owner’s input, creates an action plan that the owner will likely follow. The goal of the action plan is to help keep the pet in good health.

The screening assessment includes a checklist of the following risk factors for obesity:

• Altered gastrointestinal function (for example, vomiting, diarrhea, flatulence, and constipation),
• Previous or ongoing medical condition or disease,
• Current medications and/or dietary supplements,
• Unconventional diet (for example, a raw, homemade, vegetarian, or vegan diet),
• More than 10 percent of the pet’s daily calories from snacks, treats, and table food,
• Uneducated pet owner regarding how much, or what diet, to feed the pet, and
• Inadequate or inappropriate housing (for example, the pet is caged much of the day and doesn’t get enough exercise).

The screening assessment also includes a checklist of physical examination factors for the veterinarian to evaluate:

• Body condition score (a body fat score based on body shape and how the body feels as the veterinarian runs his or her hands over the pet),
  • 1 to 5 point scale, with 2.5 to 3 as the target scores
  • 1 to 9 point scale, with 4 to 5 the target scores
• Muscle condition score: mild, moderate, or marked muscle wasting (muscle loss),
• Unintended weight loss of 10 percent or more,
• Dental abnormalities or disease,
• Poor skin or hair coat, and
• New medical condition or disease.

If the veterinarian finds that the pet has any of the risk factors for obesity on the checklists, the guidelines suggest performing a more in-depth, or “extended” evaluation.

The screening assessment above and the extended evaluation for a pet at-risk for nutrition-related disease revolve around what the American College of Veterinary Nutrition (ACVN) calls the “Circle of Nutrition.” According to ACVN, a comprehensive approach to animal nutrition can be represented as a circle containing three interrelated components. Each component represents a different nutritional aspect for veterinarians to assess in each patient:

The Pet
“Animal-specific factors” include basic information about the pet, such as age and level of activity, and if the pet has any health issues. This information helps the veterinarian determine the appropriate nutrition for the pet. For example, a young pet has different nutritional requirements than a senior pet, and a hunting dog needs more calories than a lapdog.

The Pet’s Diet
“Diet-specific factors” determine if the pet’s diet is appropriate and safe. For example, the owner may be inappropriately feeding puppy food to a senior dog, or the diet may have recently been recalled for safety concerns. Some of the safety concerns related to pet food include:

• Improper storage, whether at the warehouse or the owner’s house,
• Adulteration, like the melamine tragedy,
• Contamination with disease-causing bacteria, like salmonella or listeria, or toxins made by fungi, like aflatoxin, and
• Nutrient imbalances, such as the past pet food recalls on thiamine-deficient diets and diets containing too much Vitamin D.

Feeding Management and Environmental Factors
Feeding management and environmental factors include information like:

• How much food does the owner feed the pet and how often?
• Does each pet have a separate food bowl or is there a shared food bowl?
• Does the pet get treats, and if so, how many? (Treats add extra calories that owners may not think about.)
• Is there competition among pets in the house such that one pet gets more food than the others?

Besides providing veterinarians with sample checklists, the AAHA guidelines also give examples of body and muscle condition scoring systems. The guidelines recommend that, in addition to being weighed (preferably on the same scale each time), every dog and cat should have a physical evaluation of its body and muscle condition at each visit. All veterinarians in the clinic should use the same scoring system to ensure the scores are more consistent. These scores will vary somewhat because they are subjective, meaning they are based on a veterinarian’s opinion of the pet’s body at that time.

The body condition scoring (BCS) system is easy to learn and requires little effort to record in the chart. The BCS system uses pictures, words, and numbers to help veterinarians and their staff quickly determine body fat levels in dogs and cats. Optimum body condition scores for cats and dogs range from 2.5 to 3 on a 5-point BCS scale, to 4 to 5 on a 9-point BCS scale. The system’s pictures are helpful in showing what pets look like at various scores. The written descriptions, although potentially a bit too technical for pet owners, describe what a pet should look and feel like at each score.

The AAHA guidelines give an example of a 9-point scale.

For an example of a 5-point scale, visit the Association for Pet Obesity Prevention’s website.

Unlike the body condition scoring system, which measures body fat, the muscle condition scoring (MCS) system looks at the amount of muscle an animal has (muscle mass). Like the BCS system, the MCS system uses pictures and written descriptions but no number score is assigned. Muscle mass is determined by pressing specific bony points on a pet’s body and seeing how far the veterinarian’s finger sinks into the body. Veterinarians can’t easily feel those points if the pet has a lot of muscle mass. As a pet loses muscle mass (muscle wasting), the bony points become easier to feel. Veterinarians describe the degree of muscle mass loss as “mild,” “moderate,” or “severe.” Sick pets are more likely to lose muscle mass, which can decrease their immunity, physical strength, and ability to heal wounds.

An action plan is only successful if it is followed by the owner. The responsibility for success is shared by the veterinarian and the pet owner. Open communication is crucial during the nutritional assessment, action plan creation, and follow-through stages. Veterinarians need to give pet owners the reasons for the action plan recommendations. Pet owners need to be honest and let the veterinarian know when they feel they cannot carry out certain recommendations. In the end, both parties want the pet to be healthy.