How Fresh Food Works: From Nutrient Profile to Metabolic Response

Key summary

Why is protein density important?

Protein requirements do not fall in proportion with calorie needs. Dogs that are desexed, less active, older, or losing weight may need fewer calories while still requiring enough protein to support lean muscle, normal immune function, tissue repair, and healthy skin and coat.

How does carbohydrate content affect the post-meal response?

Different macronutrient profiles can produce different glucose and hormonal responses after eating. In a University of Sydney crossover study, dogs fed Lyka had a lower post-prandial glucose response, alongside differences in GIP and PYY, compared with when they were fed an extruded kibble diet.

Why look beyond total fat?

The type of fat is important. EPA and DHA can be used directly by the body, while plant-derived ALA must first be converted, and that conversion is relatively inefficient in dogs.

What does moisture add?

Fresh diets contain substantially more water than dry diets. This increases dietary water intake and food volume per calorie, which may be useful when satiety and portion control are priorities.

Can we identify one feature responsible for the benefits?

Not reliably. Fresh and extruded diets often differ in several ways at once, so the biological response reflects the whole nutritional package rather than one isolated ingredient.

Protein density deserves a closer look

A dog’s energy requirement can change considerably with age, desexing, activity level, and body condition. Protein requirements do not fall at the same rate.

That becomes particularly relevant when calorie intake is reduced. If a dog eats fewer calories, each calorie needs to deliver enough protein to support lean muscle and normal body function.

This is where the protein-to-energy ratio becomes useful.

A diet may meet minimum protein requirements at a standard energy intake, but provide less protein than an individual dog needs once calories are restricted.

Image for illustrative purposes only.

That has practical consequences. Lean body mass helps preserve mobility and metabolic function, while also supporting recovery. Protein is also needed for immune responses, tissue repair, digestive enzymes, skin, and coat health.

“One of the biggest risks during a weight-loss programme is the loss of lean muscle mass… Some diets that are sitting close to the AAFCO minimums for protein may not be enough for that dog.” – Dr. Alex England.

For dogs with lower energy requirements, including those that are sedentary, desexed, older, or overweight, looking at protein relative to energy intake gives a more useful clinical picture than crude protein percentage alone.

Macronutrients shape the post-meal response

Protein, fat, and carbohydrate also influence what happens after the meal is eaten.

In the University of Sydney randomised crossover study, dogs fed Lyka showed a lower post-prandial glucose response compared with when they were fed an extruded kibble diet¹. Differences were also seen in GIP and PYY, hormones involved in post-meal metabolic and appetite signalling.

These markers give us a window into how the body is handling the meal.

A lower glucose response suggests a different pattern of carbohydrate absorption and glucose regulation after eating, while changes in gut hormones such as GIP and PYY reflect differences in nutrient sensing and appetite-related signalling.

The diets differed in several respects, including protein, carbohydrate, processing, and moisture content, so the findings cannot be attributed to one macronutrient alone.

They do show that the nutritional profile of the meal can influence how the body responds in the hours after eating.

For clinicians, that makes macronutrient composition useful to consider alongside total calorie content, particularly when supporting dogs with weight, satiety, or metabolic concerns.

The type of fat deserves attention too

Total fat percentage gives only part of the picture. Different fatty acids have different biological roles, and the source of those fatty acids can affect how efficiently they are used.

Omega-3 fatty acids such as EPA and DHA are particularly relevant because they can be used directly by the body and contribute to cell membrane function and normal inflammatory signalling, with wider roles in neurological and cardiovascular health.

“The classic one we talk about is the omega 6:3 ratio. A systematic review of studies in dogs² found that a ratio below 5.5:1 is the anti-inflammatory range, and beyond that may be pro-inflammatory.” – Dr Alex England

Plant-derived alpha-linolenic acid, or ALA, can also contribute omega-3s, but it must first be converted into EPA and DHA. That conversion is relatively inefficient in dogs.

This means two diets with a similar total fat percentage can still deliver very different fatty-acid profiles.

A year-long feeding study in senior dogs found higher circulating EPA and DHA in dogs fed a fresh diet compared with dogs fed extruded kibble³. The fresh-fed dogs also had higher levels of several compounds associated with antioxidant status.

Those differences reflect the ingredients chosen, the source of omega-3s, and what happens to the food during processing and storage.

Clinically, this means looking at where dietary fat comes from can be more informative than looking at the total percentage alone.

Moisture changes the nutritional package

Fresh diets typically contain around 65–80% moisture, compared with approximately 8–10% in dry diets.

A higher-moisture diet provides more food volume for the same number of calories. For dogs eating a controlled energy intake, that can help create a more substantial meal without increasing calorie delivery.

It also increases the amount of water consumed through food. This can be useful when supporting dogs that naturally drink relatively little or when additional dietary moisture is desirable.

Meal format also affects how easily a feeding plan can be followed. When pet parents measure food using cups or scoops, small differences in portion size can accumulate over time. Pre-portioned meals reduce some of that variation by calculating the feeding amount around the individual dog. This becomes especially useful where calorie intake needs to remain consistent from day to day.

Looking at the whole bowl

Protein density, carbohydrate content, fatty-acid profile, moisture, fibre, and food volume all sit within the same meal.

A higher-protein meal may influence satiety and lean mass support. Carbohydrate content can affect post-meal glucose response. Fatty-acid sources influence the types of omega-3s delivered. Moisture changes food volume and dietary water intake.

At the same time, processing affects the finished food, and ingredient composition influences what eventually reaches the gut microbiome.

This is why nutritional studies comparing fresh and extruded diets need to be interpreted as comparisons between whole diets. The University of Sydney study is a good example. The dogs showed differences in glucose response, gut hormones, stool quality, and microbiome diversity, while the two diets differed in several nutritional and physical characteristics.

Trying to assign every outcome to a single nutrient would oversimplify what the dogs were actually eating. The more useful clinical approach is to look at the nutritional architecture of the entire diet.

For veterinary teams, the useful question is how the whole nutritional profile fits the individual patient, including protein density, carbohydrate load, fatty-acid sources, and meal format.

Fresh feeding becomes more clinically useful when we look beyond the ingredient list and consider what the complete diet is designed to deliver.

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References

1. Campbell L, Thompson M, Muir M, Raubenheimer D, Holmes A. (2026). Diet-induced metabolic and faecal microbiome responses in pet dogs fed a minimally processed versus extruded kibble diet. Frontiers in Veterinary Science. 13:1734572. doi:10.3389/fvets.2026.1734572

2. Vendramini THA, Marchi PH, Olivindo RFG, Pedrinelli V, Amaral AR, Miranda MS, Príncipe LA, Cesar CGL, Zafalon RVA, Perini MP, Lima LOC, Balieiro JCC, Brunetto MA. (2025). Exploring the efficacy and optimal dosages of omega-3 supplementation for companion animals. Nutrition Research Reviews. 38(2):859–874. doi:10.1017/S0954422425100115 

3. Yamka R, Sires R, Wakshlag J, Huson HJ. (2025). Serum Metabolomics of Senior Dogs Fed a Fresh, Human-Grade Food or an Extruded Kibble Diet. Metabolites. 15(10):676. doi:10.3390/metabo15100676