The Truth About Carbs in Dog Food: Myths, Net Carbs, and What the Science Actually Says

If you've ever read a pet food forum, you've probably seen it: "Plant-based dog food is too high in carbs." It's one of the most repeated concerns about diets built around ingredients like chickpeas, oats, and sweet potato. But here's what often gets lost in that conversation: not all carbohydrates work the same way in your dog's body. Fiber, for example, is technically a carbohydrate, but it doesn't raise blood sugar or contribute to caloric load the way starch does. Understanding the difference, specifically what nutritionists call net carbohydrates, changes the picture entirely. This post breaks down the science of how dogs actually digest carbs, tackles the most common myths about carbs in plant-based diets, and shows you how to use net carbs as a more accurate lens for evaluating dog food.

What Are Carbohydrates in Dog Food?

Carbohydrates are a broad category that includes starches, sugars, and fiber. In commercial dog food, nearly all carbohydrates come from plant-based ingredients: grains like oats and barley, legumes like chickpeas and lentils, and vegetables like sweet potato and pumpkin. The carbohydrate percentage you see on a pet food label, or calculate from the guaranteed analysis, includes all of these together.

This matters because not all carbohydrates behave the same way in the body. Starches and sugars are digestible: they break down into glucose and enter the bloodstream. Dietary fiber, on the other hand, is largely indigestible by the enzymes in a dog's gut. Soluble fiber is fermented by gut bacteria and plays a role in microbiome health. Insoluble fiber passes through largely intact, adding bulk to stool and supporting digestive motility.

Why the Total Carb Number Can Be Misleading

When pet food critics point to a food's "high carb content," they're typically citing a number that bundles together digestible starch and non-digestible fiber. A food with 40% calculated carbohydrates but 18% total dietary fiber is very different, metabolically, from one with 40% carbs and only 3% fiber. The first food has a fraction of the metabolic carbohydrate load of the second. Looking only at total carbs obscures this distinction entirely.

This is why the concept of net carbohydrates — total carbohydrates minus total dietary fiber — offers a more useful way to compare dog foods. We'll cover the math in detail later in this post.

6 Common Myths About Carbs and Plant-Based Dog Diets

Myth 1: "Plant-based diets are just carb dumps"

This framing treats all plant ingredients as nutritionally equivalent to white rice or corn syrup. In reality, ingredients like chickpeas, oats, and lentils are complex whole foods that deliver protein, fiber, essential fatty acids, vitamins, and minerals alongside their carbohydrate content. A well-formulated plant-based diet is built around these whole food ingredients, not refined starches. The fiber content that comes with them is part of what makes total carb comparisons misleading.

Myth 2: "Dogs should eat like their wolf ancestors — raw, meat-heavy, carb-free"

Much of the carb skepticism in dog food traces back to the "ancestral" or "paleo" diet movement, which applies to pets what it argues for humans: that we should eat the way our prehistoric predecessors ate, before agriculture introduced grains and starchy foods. In the dog food world, this framing shows up most clearly in raw and ultra-meat-centric diets, marketed on the idea that dogs are fundamentally wolves and should eat accordingly.

The problem is that the wolf-diet premise doesn't hold up to the genomic record. Dogs and wolves diverged from a common ancestor and spent thousands of years co-evolving alongside farming human communities — eating scraps, grains, and plant material alongside whatever protein was available. That co-evolution produced the AMY2B gene expansion and other starch-digestion adaptations we cover in the next section. A domestic dog is not a wolf in a collar. Treating them as metabolically identical ignores the most fundamental genetic distinction between the two species.

The paleo framing also tends to conflate "ancestral" with "optimal." Even if early dogs ate a certain way, that doesn't automatically make it the healthiest choice for a modern, domesticated animal with veterinary care, longer life expectancy, and very different activity levels. Nutritional science for dogs — like for humans — is best guided by evidence, not by a reconstruction of prehistoric eating patterns.

Myth 3: "Dogs are carnivores who can't handle carbs"

Dogs are not obligate carnivores — they're omnivores. Tufts University's Cummings School of Veterinary Medicine notes that dogs can obtain up to approximately 75% of their daily calories from carbohydrates, and that one of the most dramatic genetic distinctions between dogs and wolves is the expansion of genes involved in starch digestion. We'll dig into the genetics in the next section. The short version: dogs have been biologically adapting to carbohydrate-containing diets for thousands of years.

Myth 4: "Grain-free means low-carb"

This is one of the most persistent misconceptions in pet nutrition. Grain-free formulas often substitute grains with potatoes, cassava, or high concentrations of legume flours — which are just as starchy, or in some cases starchier, than the grains they replaced. Removing grains doesn't reduce a food's carbohydrate content; it simply changes the source of those carbohydrates. If low metabolic carb load is your goal, the total dietary fiber content matters far more than whether a food contains grains.

Myth 5: "Fiber doesn't count because it's not nutritious"

Fiber is genuinely valuable. Soluble fiber feeds beneficial gut bacteria and supports a healthy microbiome. Insoluble fiber helps regulate stool consistency and supports digestive transit. Ingredients like pumpkin, oats, barley, chickpeas, and flaxseeds are all meaningful sources of dietary fiber, which is why foods built on these ingredients tend to have substantially more total dietary fiber than conventional dry dog foods. Treating fiber as a non-nutrient misunderstands its role in gut health.

Myth 6: "High carb always means poor quality"

This conflates ingredient quality with macronutrient percentage. It's true that low-quality dry dog foods often use cheap refined starches as caloric fillers, and that concern is legitimate. But the same total carbohydrate number in a food made from organic chickpeas, whole oats, and pumpkin represents a very different nutritional profile: one with meaningful fiber content, antioxidants, and whole-food micronutrients. The carb source and the fiber content together tell you far more about a food's quality than the total carb percentage alone.

How Dogs Evolved to Digest Carbohydrates

The scientific case for dogs' carbohydrate-digesting ability is well-established in the genetic literature. A landmark 2013 study published in Nature by Axelsson and colleagues found that dog domestication was accompanied by significant changes in three genes involved in starch digestion: AMY2B (pancreatic amylase), MGAM (maltase-glucoamylase), and SGLT1 (a glucose transporter). These genetic changes aren't minor variations — they represent the digestive system of a species adapting to a new food environment over thousands of years.

The AMY2B Gene: Dogs vs. Wolves

The most striking of these adaptations involves the AMY2B gene, which codes for pancreatic amylase — the enzyme that begins breaking starch into digestible sugars in the small intestine. Research published in Animal Genetics found that wolves typically carry around two copies of AMY2B, while dogs carry between four and thirty or more copies, with an average that is roughly sevenfold higher than in wolves. More copies of the gene are associated with higher levels of circulating pancreatic amylase, meaning dogs produce substantially more of this starch-digesting enzyme than their wild ancestors.

This wasn't a coincidence. Research indicates that the AMY2B expansion in dogs tracks closely with the spread of agriculture in human populations. A 2016 study in Royal Society Open Science found evidence of AMY2B gene expansion in ancient European dog genomes dating back at least 7,000 years, coinciding with early farming communities in Southeastern Europe. As humans began growing grain-based crops and sharing food scraps with the dogs living alongside them, those dogs that could more efficiently digest starch had a survival advantage — and that advantage was selected for, generation after generation.

What This Means for Modern Dogs

It's worth noting that AMY2B copy numbers vary among individual dogs and breeds. Dogs from regions with long agricultural histories (like most European breeds) tend to carry more copies than those from regions with little historical farming, like Arctic sled dog breeds or Australian dingoes. This variation means that individual dogs may differ in how efficiently they process starch. It doesn't mean carbohydrates are harmful to dogs broadly — it simply means that, as with most nutritional questions, there isn't one universal answer.

The broader takeaway is clear: dogs are not wolves, and the argument that dogs "aren't designed" to digest plant carbohydrates ignores thousands of years of documented evolutionary change. Domestic dogs have been adapting to carbohydrate-containing diets since before the pyramids were built.

What Are Net Carbohydrates and Why Do They Matter?

Net carbohydrates represent the portion of total carbohydrates that are actually digested and absorbed as glucose. The calculation is straightforward: Net Carbs = Total Carbohydrates − Total Dietary Fiber. Because dietary fiber is not digested by the enzymes in the small intestine, it doesn't raise blood sugar or contribute to the same caloric and metabolic effects as starch. Subtracting fiber from total carbs gives you a number that more accurately reflects a food's glycemic impact.

There Is No "Right" Carb Percentage for Dogs

Before diving into the math, it's worth addressing a question that comes up often: how many carbs should a dog eat? The answer, according to the veterinary nutrition community, is that no one really knows — and there is no official target. Neither AAFCO nor the National Research Council sets a recommended carbohydrate percentage for adult dog maintenance, which is part of why carbohydrates aren't required to appear on pet food labels at all. Whole Dog Journal has described the optimal carbohydrate level as one of the most hotly contested subjects in canine nutrition, with specialists unable to agree on a figure.

The only directional guidance that exists is context-specific: dogs with high energy demands or those in growth phases are generally advised to consume at least 20% carbohydrates, while dogs with diabetes or certain metabolic conditions may benefit from lower digestible carbohydrate intake. For the average healthy adult dog, the evidence points less to a specific number and more to the importance of carbohydrate quality and metabolic impact — which is exactly where net carbs become useful. Rather than chasing a percentage that nutrition science hasn't defined, net carbs give you a practical way to understand what a food is actually delivering metabolically.

Why Standard Labels Don't Tell the Full Story

Most dog food labels are required to show crude fiber as a maximum, not as an actual measured value — and crude fiber is not the same as total dietary fiber. Crude fiber testing captures only a fraction of the insoluble fiber in a food and misses soluble fiber entirely. Total dietary fiber, which includes both soluble and insoluble fractions, can be significantly higher than the crude fiber figure. A food with 6% crude fiber on its label might actually contain 16–18% total dietary fiber. Without lab-tested total dietary fiber data, calculating meaningful net carbs from a pet food label isn't possible.

This is why transparency in nutritional testing matters. When a company publishes actual lab-measured total dietary fiber data alongside calculated carbohydrates, consumers can calculate net carbs with accuracy. When only the guaranteed analysis is available, comparisons across brands are imprecise at best.

Why Whole-Food Fiber Sources Matter

Not all fiber comes in forms that are equally beneficial. Whole food ingredients like chickpeas, oats, barley, pumpkin, and flaxseeds deliver fiber alongside a range of other nutrients. This is different from isolated fiber additives (like beet pulp or powdered cellulose) that are sometimes added to lower-quality foods primarily to create a feeling of fullness. When a food's fiber content comes from recognizable whole-food ingredients, it's more likely to deliver the microbiome and digestive benefits that make fiber genuinely valuable.

Net Carbs in Petaluma's Formulas

Petaluma publishes full nutritional lab analyses for all formulas, including lab-measured total dietary fiber. This makes it possible to calculate actual net carbohydrates rather than estimating from label guarantees. The numbers below are drawn from Q1 2026 laboratory testing averaged across multiple production lots.

One distinction worth understanding: the crude fiber figure on the product label represents the maximum as required by AAFCO labeling rules. The total dietary fiber in the table below is lab-measured and includes both soluble and insoluble fractions, which is why it's substantially higher than crude fiber alone.

Nutrient (per cup)	Adult Baked Food	Senior Baked Food	Whole Food Mixer
Calories	405 kcal	390 kcal	332 kcal
Total Carbohydrates	43 g	43 g	42 g
Total Dietary Fiber (lab-measured)	18 g	19 g	17 g
— Soluble Fiber	3 g	4 g	6 g
— Insoluble Fiber	15 g	15 g	11 g
Crude Fiber (label max)	6%	6.5%	4.5%
Net Carbohydrates (calculated)	25 g	24 g	25 g

Across all three formulas, roughly 40% of total carbohydrates are dietary fiber rather than digestible starch. The net carbohydrate figures — 25g per cup for the Adult and Whole Food Mixer, and 24g per cup for the senior formula — reflect the actual metabolic carbohydrate load, and give a truer basis for comparison than total carb percentages alone. One number worth highlighting: the Whole Food Mixer carries 6g of soluble fiber per cup, double the Adult formula's 3g. Soluble fiber is the fraction that feeds gut bacteria and supports microbiome health, making the Mixer a particularly fiber-diverse option when used as a topper or mix-in.

Where the Fiber Comes From

Petaluma's fiber content comes from whole-food ingredients rather than isolated fiber additives. In the Adult formula, organic chickpeas, organic oats, organic barley, and organic flaxseeds contribute the bulk of dietary fiber. The senior formula adds pumpkin to the mix — a source of both soluble and insoluble fiber that supports digestive regularity, a priority in older dogs. The Senior formula's slightly higher total dietary fiber (19g vs. 18g per cup) reflects this pumpkin inclusion.

For more on how the senior formula is formulated to support aging dogs specifically, see our post on senior dog nutrition. And for a deeper look at fiber's role in gut health, our post on dietary fiber for dogs covers the latest research on soluble and insoluble fiber sources.

Frequently Asked Questions

Are carbohydrates bad for dogs?

Carbohydrates are not inherently harmful to dogs. Dogs have evolved specific genetic adaptations for starch digestion over thousands of years alongside human agricultural communities. The quality and source of carbohydrates matters more than the total carbohydrate percentage — whole food sources like chickpeas, oats, and pumpkin deliver fiber, vitamins, and minerals alongside their carbohydrate content, in contrast to refined starches used as inexpensive caloric fillers.

How do you calculate net carbs in dog food?

Net carbs = total carbohydrates − total dietary fiber. To do this accurately, you need lab-measured total dietary fiber data, not the crude fiber figure on the guaranteed analysis label. Crude fiber testing captures only a portion of total dietary fiber (primarily insoluble fiber) and misses soluble fiber entirely, so it significantly underestimates how much fiber a food actually contains. Contact the pet food company directly, or look for published nutritional analyses that include total dietary fiber.

Why do plant-based dog foods appear high in carbohydrates?

Plant-based dog foods use whole food ingredients like legumes, grains, and vegetables, which naturally contain carbohydrates alongside their protein and fiber. Importantly, these same ingredients also tend to deliver significantly higher total dietary fiber than meat-based dry foods. When you account for fiber and calculate net carbohydrates, the metabolic carbohydrate load of a well-formulated plant-based food is often lower than the total carb number suggests.

Does grain-free dog food have fewer carbohydrates?

Not necessarily. Grain-free dog foods typically substitute grains with potatoes, cassava, tapioca, or high concentrations of legume flours — all of which are starchy carbohydrate sources. In some cases, grain-free formulas have higher total carbohydrate content than grain-inclusive alternatives. Whether a food is grain-free tells you nothing reliable about its carbohydrate level or net carb content.

What is the AMY2B gene and what does it tell us about dogs and carbs?

AMY2B codes for pancreatic amylase, the enzyme that begins breaking starch into digestible sugars in the small intestine. Dogs carry an average of roughly seven times as many copies of this gene as wolves, which is associated with significantly higher amylase activity and improved starch digestion. This expansion occurred over thousands of years as dogs lived alongside farming human communities. It's one of the clearest pieces of genetic evidence that domestic dogs are well-adapted to diets that include carbohydrates.

Is fiber a carbohydrate?

Yes — biochemically, fiber is classified as a carbohydrate. But unlike starch and sugars, dietary fiber is not digested by the enzymes in the small intestine, so it doesn't raise blood glucose or contribute to the same caloric effects. Soluble fiber is fermented by gut bacteria and supports microbiome health; insoluble fiber supports stool consistency and digestive motility. Because fiber behaves so differently from digestible carbohydrates, it's subtracted when calculating net carbs.

How much fiber should a dog get per day?

There is no AAFCO minimum for dietary fiber, as it is not classified as an essential nutrient in the same way protein or fat are. That said, many veterinary nutritionists recognize the functional benefits of appropriate fiber levels for digestive health and stool quality. The right amount varies by individual dog, health status, and activity level. Dogs with specific conditions such as diabetes, obesity, or certain digestive issues may benefit from higher or specifically balanced fiber intake — consult your veterinarian for guidance tailored to your dog.

References

1. Axelsson E, Ratnakumar A, Arendt ML, et al. The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature. 2013;495(7441):360–364. pubmed.ncbi.nlm.nih.gov/23354050
2. Arendt M, Fall T, Lindblad-Toh K, Axelsson E. Amylase activity is associated with AMY2B copy numbers in dog: implications for dog domestication, diet and diabetes. Animal Genetics. 2014;45(5):716–722. pmc.ncbi.nlm.nih.gov/PMC4329415
3. Ollivier M, Tresset A, Bastian F, et al. Amy2B copy number variation reveals starch diet adaptations in ancient European dogs. Royal Society Open Science. 2016;3(11):160449. pmc.ncbi.nlm.nih.gov/PMC5180126
4. Rankovic A, Adolphe JL, Verbrugghe A. Role of carbohydrates in the health of dogs. J Am Vet Med Assoc. 2019;255(5):546–554. pubmed.ncbi.nlm.nih.gov/31429654
5. Tufts University Cummings School of Veterinary Medicine. Carb Confusion Part 1: The Role of Carbohydrate in Pet Foods. petfoodology.com. 2021. sites.tufts.edu/petfoodology
6. Ivanović S, Becskei Z, Radinović M, et al. Copy number variations in AMY2B gene and amylase activity in Balkan dog breeds. PLOS ONE. 2025. pmc.ncbi.nlm.nih.gov/PMC12047765