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Are You Falling for the Biggest Pet Diet Scam?

Discover why therapeutic diets might fail your furry friends and what alternatives can help them shed those extra pounds.

therapeutic prescription diets


  • Overweight and obesity in dogs and cats is a physiological disorder affecting numerous body systems, often causing secondary, preventable diseases, including diabetes, osteoarthritis, and many forms of cancer
  • According to the results of the 2022 pet owner survey conducted by the Association for the Prevention of Pet Obesity (APOP), therapeutic “prescription” diets for weight loss are of little use in helping overweight dogs and cats slim down
  • It seems pet parents have lots of different reasons for either not trying the diets at all, or abandoning them fairly quickly; fortunately, in my experience, there are far better ways to help too-heavy pets slim down and enjoy healthier lives
  • Parents of porky pets must first acknowledge their dog or cat is overweight, then throw out the carb-heavy ultraprocessed diets, feed the right number of calories for weight loss, and kick-off a daily exercise routine

According to the Association for the Prevention of Pet Obesity (APOP) 2022 survey,1 pet parents are having some success getting weight off their dogs and cats; however, therapeutic “prescription” diets haven’t proved to be very helpful in addressing the issue.

“Therapeutic weight loss diets are the primary evidence-based treatment veterinary professionals have to help an overweight pet attain a healthy body composition,” the authors of the APOP report wrote. “The fact that only about one in five owners of overweight pets in our survey reported they have tried a therapeutic weight loss diet indicates a gap in education and compliance.”2

In my opinion, the fact that pet parents are avoiding ultraprocessed weight loss pet food is a good thing. It’s a shame but unsurprising that these diets are “the primary evidence-based treatment” available to veterinary professionals.

We’re seeing an explosion of “prescription” diets advertised for dogs and cats with a wide range of health conditions such as kidney or liver disease, joint disease, obesity, food intolerances, gastrointestinal (GI) disorders, cognitive dysfunction, urinary crystals and stones, diabetes, heart disease, cancer, dental disease, and recovery from an accident, surgery, or illness.

The mainstream pet food industry as well as many in the conventional veterinary community are working hard to convince pet parents that processed so-called therapeutic or prescription diets are “food as medicine” and the wave of the future.3

I think fresh food diets made with human-grade human ingredients designed for overweight pets and those with specific health conditions are a great idea. Unfortunately, what you get with a processed prescription diet is simply a modified version of the same feed-grade ingredients found in non-prescription pet food.

In my experience and that of other integrative veterinarians, highly processed diets made with feed-grade ingredients are the root cause of overweight/obesity and many of the diseases pets acquire today. It’s reprehensible that when a dog or cat becomes sick with degenerative diseases after years of eating processed, biologically inappropriate food, their owners are told to buy a more expensive version of a similar food and consider it “medicine.”

Therapeutic, Prescription Diets Ranked Least Effective

According to the 2022 APOP survey results:

  • 54% of dog owners and 56% of cat owners ranked either reducing calories or feeding smaller portions as the most effective way to help their pets lose weight
  • 54% of dog owners ranked stopping or reducing treats as the second most effective approach
  • 47% of cat owners ranked measuring food as second
  • Only 11% of dog owners and 23% of cat owners found therapeutic or prescription diets as the most effective

The APOP report authors note that:

“Therapeutic pet weight loss diet usage remains at the bottom of our pet owner rankings in both pet [weight] loss methods and perceived efficacy. These findings are consistent with our findings in 2018, when 19% of pet owners stated they had tried a therapeutic weight loss diet to help their pets lose weight.”4

Why Commercial Weight Loss Pet Formulas Don’t Fly

The APOP report authors suggest a range of factors that may influence pet owner perception of prescription weight management diets as effective, including:

  • Perceived higher costs of therapeutic diets
  • Lack of easy access to specific brands or formulations
  • Changes in fecal output or other physical factors during diet transition
  • Lack of significant or timely improvement

For their part, veterinary professionals may be hesitant to suggest such diets due to cost, lack of ability to support or monitor a weight loss plan, lack of understanding of the health risks of overweight/obesity, widespread nutritional misinformation and confusion, and/or negative pet owner perception of “vets selling food.”

Humans Don’t Excel at Helping Their Pets Lose Weight

The 2022 APOP survey involved both veterinarians and pet owners. A total of 1,152 dogs and cats were evaluated — 880 dogs and 272 cats. Pet owners completed 403 surveys about their dogs' or cats' weight, nutrition and pet food.

While nearly half of those surveyed reported some weight loss for their dog or cat when they made the effort, 12% of dog owners and 5% of cat owners said their pet gained back the lost weight.

A significant 23% of dog and 29% of cat owners reported that had no success in helping their animal lose weight, or that their pet didn’t lose weight despite their best efforts.

“Obesity is a physiological disorder affecting numerous body systems,” APOP report authors wrote. “Pet obesity often causes secondary, preventable diseases, including diabetes, osteoarthritis, and many forms of cancer. Professionals and the pet care industry need to educate the pet-owning public better that pet obesity is a disease with significant harmful impacts on both quality of life and life expectancy.”5

How to Tell if Your Dog or Cat Is Overweight

Because so many pets are overweight today, many people can no longer tell the difference between a fat pet and a normal-sized pet.

If you're not sure about your own dog or cat, look down at him. Does he have a tapered in waist? If not — if he’s shaped more like an oval, he's probably too heavy. You should also be able to feel (but not see) his ribs as well as the bones near the base of his tail (the exception to this rule are sighthounds, e.g., Greyhounds, Whippets, whose ribs often show). If he's obese, you'll see obvious amounts of excess fat on his abdomen, hips, and neck.

Also compare your pet to these body condition charts provided by the World Small Animal Veterinary Association (WSAVA):

Dog Body Condition Score

Cat Body Condition Score

The goal for both dogs and cats is a body condition score of 5. Unfortunately, many owners assume their pet's body score is just fine because their veterinarian never mentions their pet has a weight issue during exams. Veterinarians fail to address extra pounds for many reasons, including because it can be an uncomfortable conversation.

I've had countless pet parents tell me I was the first vet to comment that their dog or cat needed to lose a few pounds, which tells me vets are not adequately addressing the slow but consistent weight gain that occurs over time with many pets and contributes to so many degenerative diseases that could be avoided with appropriate weight management.

Dos and Don’ts for Keeping Your Pet at a Healthy Weight

The following are several of the recommendations I offer pet parents on the best way to prevent weight gain and help pets lose weight if necessary.

  1. DON’T feed a starch-heavy, carbohydrate-laden, ultraprocessed diet — Ultraprocessed pet foods are a significant contributor to the pet obesity epidemic in the U.S. Many pet parents overfeed, but very often the problem is also the quality of food they're offering in addition to the quantity.

    If you're feeding kibble, while it might be free of grains, it can't be free of carbs, because carbs are necessary to form kibble. If you look at the package label, you'll see potato, sweet potato, lentils, peas (pea starch), chickpeas, tapioca and/or other carbohydrate sources. Starch breaks down into sugar, even though you don't see sugar on the pet food package label. Carbs that aren’t burned for energy are stored as fat.

    Many dry pet foods are heavy in carbs (40% to 50% of total content in some cases), which can lead to blood sugar fluctuations, insulin resistance, obesity, diabetes and other health problems in pets. Carb intake above the daily needs of your pet (less than 10%) activates internal enzyme factors that go to work storing the excess as body fat.

    Calculate the carbs in your pet’s dry diet by adding up the moisture, fat, protein, fiber, and ash (estimate 6% if you don’t see it listed) on the pet food label and subtract this value from 100: this is the amount of soluble carbs in your pet’s diet (aka sugar).

    DO feed your pet fresh food — Cats and dogs need food high in animal protein and moisture, with low to no grain or starch content (which is pretty much the opposite of what dry pet foods offer, especially grain-free kibble). A high-quality, nutritionally complete fresh food diet is the best choice for pets who need to lose weight. It's important to adequately nourish their bodies as weight loss occurs, making sure their requirements for key amino acids, essential fatty acids and other nutrients are met despite a lower calorie intake.

    The key to healthy weight loss is to meet your pet's nutritional requirements through a balanced diet but feed fewer calories and encourage more exercise, which forces his body to burn fat stores. This means the food must be formulated for less active animals. The first step is to transition him to a diet free of potatoes, corn, rice, soy, tapioca or any other vegan filler to get the carb content down to a biologically correct value of no more than 20% with a goal of less than 10% for healthy dogs and cats.

    My best recommendation is a nutritionally optimal homemade fresh food diet of lean meats, healthy essential fats, plus fibrous vegetables and low glycemic fruits as the only sources of carbohydrates. These “healthy” carbs are the perfect way to maintain your pet’s microbiome, while providing fiber, antioxidants, and phytonutrients. Homemade diets formulated for less active animals give you ultimate quality control over the ingredients going into your pet’s body.

    If you can’t prepare your pet’s meals, partner with a transparent company happy to discuss ingredient sourcing, quality control and formulation details with you. You can also create nutrient-dense recipes specifically formulated for less active dogs and cats with the Animal Diet Formulator or have their vets formulate a custom diet for you.
  2. DON’T free feed — Also known as feeding ad libitum or the all-day all-they-can-eat buffet, this mistake by necessity goes hand-in-hand with a poor-quality diet, specifically kibble, because it's the only type of food you can safely leave at room temperature 24/7. Free feeding is the perfect way to wind up with an overweight or obese pet. In addition, a constantly available food source turns your carnivorous hunter into a grazer, which goes against her nature.

    Wild cats and dogs are always on the move in search of their next meal; they are fasting and exercising in between meals. Many domesticated pets, on the other hand, are free fed. Many pets and people graze all day, which results in chronically elevated blood sugar, a constant demand for insulin (increasing the likelihood of insulin resistance), the over consumption of calories and circadian rhythm disruption.

    A growing body of research on animal models demonstrates time restricted feeding (TRF) translates into healthier, longer-lived animals with fewer metabolic diseases.6 I have found this to be the cheapest and easiest way to create health, especially if you can’t feed an ideal, fresh food diet or maintain an ideal exercise schedule for your animals.

    My suggestion is to aim for an 8-10 hour feeding window: feed your pet’s meal(s) and all training treats within 10 hours (with a 14-hour fasting period) which allows ample time for the body’s reparative and restorative processes to unfold, according to their inner biologic clocks.

    DO challenge your pet at mealtime — Separate your pet’s daily food allocation into several small portions and place them in different locations around the house for her to find. Make use of food puzzle toys for dogs and indoor hunting feeders for cats, which encourage hunting behavior and provide mental stimulation.

    Also consider putting food bowls at the bottom and top of your staircase if you have one to encourage muscle-building and glucose-burning exercise throughout the day. While many people feed their pets twice a day, feeding just once a day actually offers a number of health benefits, including a lower risk of diabetes.
  3. DON’T follow pet food package feeding guidelines — Most people who feed commercially available pet food follow the suggested feeding guidelines printed on the package, which often isn’t the best approach. These recommendations typically use overly broad weight ranges such as “under 20 pounds” when clearly, a 15-pound dog requires more calories than a 5-pound dog.

    Package feeding instructions also use wide serving ranges, such as “feed 1/2 to 1 1/2 cups.” These suggestions obviously don’t consider, for example, an animal’s activity level, and they tend to be short on other important details, such as whether “feed 1/2 to 1 1/2 cups” is a daily or per-meal guideline.

    Contact the company and ask what’s the least amount of food that can be fed for your animal’s body weight without resulting in nutritional deficiencies, then divide that amount into several meals within an eight-hour “eating window,” which research also shows helps burn more body fat.

    DO feed your heavy pet to achieve weight loss — Decide (with the help of your veterinarian, if necessary) what your dog’s or cat’s ideal weight should be. Then use one of the following formulas to calculate the precise number of calories to feed daily to get your pet down to his ideal weight and maintain it.

    For example, let's say your canine BFF is 30 pounds and his ideal weight is around 22 pounds:

    Daily calories (canine) = Body weight (kg) x 30 + 70

    First, convert his weight from pounds to kilograms. One kilogram = 2.2 pounds, so divide his ideal weight (not his current weight) in pounds by 2.2. 22/2.2 means your dog's ideal weight in kilograms is 10. Now the formula looks like this:

    Daily calories = 10 (kg) x 30 + 70

    And finally, it looks like this:

    Daily calories = 370

    If you feed your dog 370 calories a day, he should drop steadily to his ideal weight of 22 pounds and maintain it.

    Let’s say your cat’s ideal weight is a slender 12 pounds rather than her current weight of 16 pounds:

    Daily calories (feline) = Body Weight (kg) x 30 + 70 x 0.8

    (The formula for cats includes a slight adjustment to account for the extremely sedentary lifestyle of most kitties these days.)

    Her ideal weight of 12 pounds divided by 2.2 converts to 5.5 kilograms; now the formula looks like this:

    Daily calories = 5.5 (kg) x 30 + 70 x 0.8

    And finally, it looks like this:

    Daily calories = 188

  4. DON’T ignore your pet’s need for exercise — You’ll never see a fat dog or cat in the wild because they follow their natural instincts, which includes the drive to be physically active. And while your Chihuahua doesn’t behave or look much like her wolf cousins, she was designed to move like they do.

    Given the opportunity and incentive, your little lap dog will walk impressive distances, hike, run, play, chase things, dig in the dirt, roll in the grass, enjoy every minute of it, and be healthier and happier for it. Only her humans, and possibly her too-heavy, uncomfortable body, are stopping her from being the little athlete she was born to be. How sad and unnecessary is that?

    DO make sure your pet gets daily aerobic exercise — Consistent daily exercise, including at least 20 minutes (and preferably 60) of aerobic activity will help your pet burn fat and increase muscle tone. If you're unable to provide your dog with this much physical activity (and some dogs require even more), consider joining a pet sports club or doggy daycare. Another option is to hire a dog walker (or dog jogger, hiker, or biker).

    If your pet is very overweight or obese, she may not be able to endure extended periods of exercise initially. Swimming is an excellent low-impact, gentle form of exercise for dogs who need to start out slow, as well as those with arthritis or mobility issues. Ask your veterinarian what exercises are safe for your pet to do, and which you either need to avoid or put off until she's in better condition. If you're dealing with a fat feline, check out Creative Strategies to Get Your Indoor Cat Moving.
  5. DON’T overfeed treats — Treats — even very high-quality healthy ones — should make up less than 10% of your dog’s or cat’s daily food intake. It's also important to remember that treats aren't a complete form of nutrition and should never be used in place of nutritionally balanced, species-appropriate meals. Overfeeding treats on top of daily food intake will result in an obese pet, and overfeeding treats while underfeeding balanced meals will result in nutritional deficiencies.

    DO feed tiny healthy treats on a very limited basis — Limit treats to training and behavior rewards only. Again, keep treats at or fewer than 10% of your pet’s daily food intake, which means offering very small pieces of healthy foods, very infrequently.

    My favorite treats are berries, other fruits that can be cubed into tiny, bite-sized morsels (e.g., melons, green bananas, and apples), frozen peas and blueberries, and raw sunflower and pumpkin seeds (pepitas). The ultimate snack for dieting dogs is bone broth ice cubes.

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