There’s a huge difference between simple sugars and complex sugars, and most people have no idea how this affects their dogs!
Commercial pet foods (kibble, tins, even many “premium” brands) are loaded with complex carbohydrates, better known as starches.
“Complex carbs” = polysaccharides
(“Poly” = many, “saccharide” = sugar)
So basically… starches are long-chain sugars — too much unhealthy sugar! 
These ingredients — grains, rice, peas, lentils, potatoes, chickpeas, etc. — are used because they’re cheap fillers and help bind kibble together. But just because dogs can survive on them doesn’t mean they thrive on them.
Starches actually rob the body of nutrients. They block proper mineral absorption and over time, can lead to issues like anaemia, dull coats, poor energy, and inflammation.
Insulin and Fat
Insulin is a hormone made by the beta cells in the pancreas. Its main job is to act like a key — it unlocks the door to the cells, allowing sugar (glucose) from the bloodstream to enter and be used for energy.
However, when there’s too much fat circulating in the bloodstream — especially from processed or damaged, unhealthy fats — it can block insulin’s ability to do its job. The fat forms a coating around the cells, making them less responsive to insulin’s signal.
This means glucose can’t enter the cells properly, so it builds up in the bloodstream. Over time, this leads to insulin resistance, which then develops into high blood sugar and eventually diabetes.
We see this in humans, and now the same metabolic issues are showing up in dogs — because their diets have shifted toward the same high-fat, high-starch, ultra-processed foods.
Unfortunately, few studies have been done on dogs, so we often rely on human research to understand these mechanisms.
For anyone curious to learn more, the documentary What the Health (2017) gives a great visual explanation of how dietary fat interferes with insulin function, leading to insulin resistance and diabetes.
Watch here: What the Health (YouTube)
Now here’s where it gets really interesting
Simple sugars, like the natural sugars in fruit (fructose) and complex sugars (starches) behave completely differently in the body.
Simple sugars — like fructose in fruit — enter cells easily through diffusion.
No insulin needed! This gentle process saves the body energy and fuels the cells directly.
Starches, on the other hand, require insulin to enter cells. When a dog eats starch, the body breaks those long chains of sugar apart, causing a huge spike in blood sugar, followed by a crash. The leftover undigested starches then ferment in the gut, feeding yeast, candida, and parasites. 👉 You can read about the role and causes of yeast overgrowth here.
And it gets worse…
These sticky starches and processed fats together cause inflammation, acidosis, and chronic strain on the body.
Acid = corrosive.
It breaks down tissues, dehydrates the body, and fuels chronic inflammation.
Over time, this constant strain on the system can show up as:
Itching & ear ‘infections’
Yeast overgrowth
Gut imbalance
Low energy
Poor coat & skin
So while many worry about giving fruit because they think it’s “too sugary,” the real issue isn’t simple sugars; it’s the complex starch sugars hidden in processed pet foods.
Fresh fruits (fed on the right days!) nourish.
Starches in kibble deplete.
Let’s stop fearing nature’s simple sugars and start questioning the complex ones that don’t belong in our dogs’ bowls 
Feeling confused about sugars and starches in your dog’s diet? You’re not alone; so many people have been taught to fear fruit sugars while unknowingly feeding the wrong kinds of sugars hiding in processed foods. I can help you clear up the confusion around sugars, starches, and fats. I can guide you through it step by step. Get in touch today, and let’s make it simple. Real food, real results naturally.
If you’d like to dive a bit deeper into what’s hiding in commercial pet foods, from fillers to synthetic additives. I’ve written a full blog. The Hidden Dangers in Commercial Dog Food
Read the full article
Canine Wellness Specialist 