Blood doesn't lie about what's been in the bowl. A 2025 study out of the University of Helsinki's DogRisk group tracked exactly what happens to a dog's metabolism over months of eating kibble, and the pattern showed up in the numbers before it showed up anywhere else.

The team followed 46 Staffordshire Bull Terriers for four and a half months, splitting them between a high-carbohydrate kibble diet and a low-carbohydrate raw meat-based diet. They drew blood the whole way through, tracking glucose, insulin, cholesterol, triglycerides, ketone bodies, and bodyweight.

The kibble group's blood sugar climbed. So did their lipids. So did the scale.

The raw-fed group moved the opposite direction. Blood sugar and lipids dropped, ketone bodies rose, and the dogs showed more signs of running on fat for fuel instead of carbohydrate. Researchers also calculated a triglyceride-glucose index, a marker used in human medicine to flag early insulin resistance, and it tracked worse in the kibble group across the study period.

Dogs didn't evolve eating bowls of starch. A kibble formula typically runs 30% to 60% carbohydrate by weight because starch is what lets the extrusion process work, not because a dog's body is built to run on it. Every one of those meals asks the pancreas to release insulin to manage a glucose spike that a raw, low-carb diet never creates in the first place. Do that twice a day for years and the weight gain and metabolic strain aren't a mystery. They're the predictable output of the input.

Here's what this trial doesn't prove: it ran on one breed, over one four-and-a-half-month window, and no independent lab has repeated it yet. That matters. A Staffordshire Bull Terrier's metabolism isn't a Chihuahua's or a Great Dane's, and a longer trial could still shift these numbers. Treat this as a strong early signal, not a settled fact across every dog.

What it does give owners is a direction backed by real bloodwork, not a guess: dogs eating raw ran cooler on every metabolic marker that matters. Ask your vet for a fasting glucose and lipid panel at your dog's next checkup. That's not a hypothetical. It's a number you can actually see, compare, and use to check the switch is working.