A new feeding study compared how healthy pet dogs responded to a gently cooked fresh diet and an extruded kibble. Researchers found measurable differences in blood glucose, digestive hormones, stool quality, and the gut microbiome, even though both foods were formulated to provide complete nutrition.

The findings add useful evidence that a diet affects more than whether nutrient minimums are met. How nutrients are supplied, combined, processed, and digested also influences what happens after the food enters the body.

How the Study Was Conducted

Researchers recruited 24 privately owned dogs between 2 and 9 years old. The dogs represented 18 breeds and weighed between 11 and 43 kilograms. They were generally healthy, with no chronic disease, recurring gastrointestinal problems, known food intolerances, recent antibiotic use, or prescription diets.

The study used a crossover design. Each dog was fed both diets, one after the other, allowing researchers to compare each dog’s response to the fresh food with that same dog’s response to kibble. After a gradual transition, each food was fed exclusively for approximately two weeks. One dog was withdrawn after developing an intolerance to the fresh diet, leaving 23 dogs that completed both feeding periods.

The fresh food was Lyka Chicken Bowl, cooked at a maximum temperature of 90°C and then frozen. The kibble was Hill’s Science Diet Healthy Mobility Adult, produced through extrusion. Both were commercial diets intended for adult maintenance.

The Diets Were Very Different

This was not simply the same recipe prepared in two different ways.

Protein supplied approximately 52 percent of calories in the fresh diet, compared with about 20 percent in the kibble. Carbohydrate supplied approximately 12 percent of calories in the fresh food and 48 percent in the kibble. The fresh food also contained considerably more moisture and used different ingredients and fiber sources.

That distinction matters. Any difference between the dogs’ responses could have resulted from processing, macronutrient balance, ingredients, moisture, fiber, food structure, or a combination of these factors.

Blood Glucose Rose Less After the Fresh Meal

The dogs had a significantly lower overall blood glucose response after eating the fresh diet. Their peak glucose level was lower, and the peak occurred sooner than it did after the kibble meal.

This was the general group pattern, but it was not universal. A few individual dogs had a lower glucose response to the kibble, reinforcing that dogs do not all respond identically to the same food.

The difference is not surprising given that the kibble provided approximately four times as much of its energy from carbohydrate. It does, however, demonstrate that two diets considered complete and balanced can produce substantially different metabolic responses after a meal.

Digestive Hormone Signaling Also Changed

Dogs had lower concentrations of GIP and PYY while eating the fresh diet, both before and after meals. Several other hormones, including insulin, amylin, GLP-1, ghrelin, and leptin, also tended to be lower, although those differences did not reach statistical significance.

These hormones are involved in nutrient sensing, appetite, digestion, and metabolic regulation. Lower values should not automatically be labeled healthier or better. The study shows that the diets stimulated different physiological responses, but it did not establish the long-term health consequences of those differences.

Stool Quality Improved

Owner-reported stool consistency was closer to the study’s ideal score while dogs ate the fresh diet. Average scores were 2.24 on the fresh food, compared with 2.87 on the kibble and 2.69 on the dogs’ original diets.

This was a statistically significant difference, although stool quality remained generally acceptable on both experimental diets.

The Gut Microbiome Shifted

Diet produced clear changes in the composition of the dogs’ fecal microbiomes. Microbial richness was generally higher during the fresh-food period, while the kibble supported lower diversity in several analyses.

The types of bacteria that increased also reflected the foods being supplied. Bacteria associated with protein metabolism were more abundant on the high-protein fresh diet, while bacteria commonly associated with carbohydrate-rich kibble diets increased during the kibble period. The researchers concluded that macronutrient distribution was probably a major driver of these microbial differences.

The individual dog still mattered enormously. Each dog retained a recognizable microbial pattern, and the magnitude and direction of change varied between dogs. A microbiome result therefore cannot be interpreted only by asking whether a particular bacterium increased or decreased.

What the Study Does Not Prove

This was a short pilot study involving healthy adult dogs. It did not test whether either diet prevents obesity, diabetes, inflammatory disease, gastrointestinal disease, or any other chronic condition. Both foods maintained the dogs’ general health during the brief feeding periods, and the researchers found no significant overall change in body weight or clear difference in inflammatory markers.

The study also cannot tell us whether the observed effects were caused by less processing. The recipes differed too much in protein, carbohydrate, moisture, fiber, ingredients, and physical structure to isolate processing as the determining factor. The authors specifically acknowledged that causal effects could not be assigned to nutrient composition or processing level and called for longer studies using more closely matched diets.

The research was co-funded by Lyka Pet Food, the manufacturer of the fresh diet, and one author was employed by the company. The authors reported that the funder was not involved in study design, data collection, analysis, interpretation, or publication decisions. This does not invalidate the findings, but it belongs in any fair assessment of the evidence.

Why These Findings Matter

“Complete and balanced” tells us whether a diet is formulated to supply established essential nutrients. It does not mean that every complete diet produces the same digestive, hormonal, metabolic, or microbial response.

This study provides additional evidence that food form and formulation matter. The gently cooked, higher-protein, lower-carbohydrate diet produced firmer stools, a lower post-meal glucose response, different digestive hormone signaling, and a richer microbial community than the extruded kibble.

It does not prove that every fresh diet is superior to every kibble, or that fresh food is automatically suitable for every dog. Recipe quality, nutrient adequacy, ingredient tolerance, medical needs, calorie control, and the individual dog still determine whether a diet is appropriate.

The real lesson is that nutrition cannot be reduced to a nutrient adequacy statement printed on a label. Meeting minimum requirements is essential, but it is only one part of how a diet interacts with the dog eating it.

Study reviewed: Campbell LC, Thompson M, Muir M, Raubenheimer D, and Holmes A. “Diet-Induced Metabolic and Faecal Microbiome Responses in Pet Dogs Fed a Minimally Processed Versus Extruded Kibble Diet.” Frontiers in Veterinary Science, published April 10, 2026.

Read the full study