5 Signs Your Dog's or Cat's Diet Isn't Working

Your pet can't tell you when something's not right with their food. They can't explain that their tummy hurts, or that their coat feels uncomfortable, or that they just don't have the energy they used to. What they can do is show you, through their body, their behaviour, and the way they feel in their own skin.

In my work as an animal naturopath, I see pets every day whose owners have been quietly worried for months or even years. They've been told everything is "normal," or they've tried different foods without seeing improvement. Often, the signs were there all along. The body was asking for something it wasn't getting.

Here are five of the most common signs I look for when a dog or cat's diet isn't meeting their needs.

1 A dull, dry, or flaky coat

A pet's coat is one of the clearest windows into what's happening on the inside. When the diet is right, fur should be soft, shiny, and smooth. When it's not, you often see the difference first in how your pet looks and feels.

Dull fur, excessive shedding, dry flaky skin, or a coat that seems brittle and lifeless are among the most common signs I encounter. In many cases, the culprit is a deficiency in essential fatty acids, particularly omega-3s. These fats are critical for skin barrier function, coat condition, and reducing inflammation throughout the body.

Many commercial dry foods are heavily processed using high heat, which destroys much of the naturally occurring fat content and leaves pets relying on synthetic additions that may not be well-absorbed. If your dog or cat is eating a "complete" food but still looks dull, that's worth investigating.

What to do: Look at the quality and source of fats in your pet's food. Fresh, whole-food fat sources tend to be far more bioavailable than synthetic additives. A naturopathic consultation can help you identify where the gap is and how to fill it.

2 Recurring digestive upsets

The occasional vomit or loose stool is not unusual for dogs and cats. But when it keeps happening, week after week, that's your pet's digestive system waving a flag.

Recurring vomiting, soft or inconsistent stools, excessive gas, grass eating (particularly first thing in the morning), or a stomach that seems to grumble constantly can all point to a diet that isn't agreeing with your pet's gut. Common culprits include food intolerances to ingredients like beef, chicken, dairy, or grains; an imbalance in the gut microbiome; or simply a food that doesn't suit that individual animal's digestive capacity.

It's also worth noting that the fibre content of commercial foods can vary enormously. Some pets need more prebiotic fibre to support their gut bacteria than their current diet provides. Others are reacting to filler ingredients that have no nutritional value.

What to do: Keep a food and symptom diary for two to four weeks. Note what your pet eats, when symptoms occur, and any patterns you notice. This kind of record is incredibly useful when working with both a vet and a naturopath to pinpoint what's going on.

3 Low energy or lethargy

It's easy to chalk a tired pet up to age, weather, or "just their personality." And sometimes that's true. But when a dog or cat is consistently low in energy, reluctant to play, or sleeping far more than usual, nutrition deserves a closer look.

Energy production at the cellular level depends on a steady supply of well-absorbed nutrients, including B vitamins, iron, magnesium, and quality protein. Heavily processed foods may technically contain these nutrients on paper, but bioavailability matters enormously. A nutrient listed on a label is not necessarily a nutrient your pet's body can access and use.

I also see lethargy in pets who are eating a diet that creates low-grade, chronic inflammation. Inflammation is energetically expensive. The body is constantly working to manage it, and there's less left over for the things your pet actually wants to do.

What to do: Consider whether your pet's food has changed recently, or whether the lethargy came on gradually over time alongside a long-term diet. Both are useful clues. A full dietary review can often reveal gaps that aren't immediately obvious.

4 Persistent itching, scratching, or skin inflammation

This is one of the most distressing signs for both pet and owner, and one of the most commonly misunderstood. Itchy, inflamed skin, recurring hot spots, paw licking, face rubbing, or ear infections that keep coming back are almost always connected to inflammation, and diet is one of the most powerful drivers of inflammation in the body.

Many commercial pet foods contain ingredients that are highly inflammatory for sensitive animals. Common offenders include artificial colours, flavours, and preservatives, certain proteins that trigger immune responses, refined carbohydrates, and low-quality fats that promote rather than calm inflammation.

For cats in particular, many commercial foods are far too high in carbohydrates for their obligate carnivore physiology. This creates a chronic metabolic stress that can show up in the skin, coat, and gut over time.

The key insight here is that itching and skin inflammation are rarely just a skin problem. They are the skin's way of expressing an internal imbalance, often driven by what's going into the food bowl.

What to do: If your pet has been through multiple courses of antihistamines or steroids without lasting relief, that's a strong signal to look at the root cause rather than the symptom. A dietary elimination approach, done properly with guidance, can be transformative for itchy pets.

5 Strange appetite or eating non-food items

Does your dog eat grass obsessively, chew on dirt or rocks, lick walls, or seem driven to eat things that aren't food? Does your cat beg constantly even after a full meal, or suddenly refuse a food they've eaten happily for years? These behaviours can look quirky or frustrating, but they often carry meaningful information.

Pica, the urge to eat non-food substances, is frequently a sign of mineral deficiency. The body, sensing it's missing something, drives the animal to seek it out. Dogs eating dirt may be seeking iron or calcium. Grass eating can reflect a need for digestive relief or additional plant-based compounds the diet isn't providing.

Constant hunger despite adequate portions often means the food lacks satiety, either because it's too low in protein, high in fillers, or simply not nutrient-dense enough to satisfy. Real hunger and nutrient hunger are different things, and commercial foods don't always address both.

Sudden food refusal can be trickier: it might reflect boredom, a change in formula by the manufacturer (which happens more than most owners realise), or a genuine sensitivity the pet has developed over time through repeated exposure to the same ingredients.

What to do: Don't dismiss these behaviours as "just what they do." They are worth paying attention to. A naturopathic assessment looks at these patterns as part of the whole picture and can help identify whether a nutritional gap is driving the behaviour.

So what now?

If you recognised your pet in any of these signs, the most important thing to know is this: it doesn't have to stay this way. Many of the chronic symptoms I work with respond remarkably well to targeted dietary changes. Not overnight, but steadily, visibly, and often in ways that genuinely surprise the owners who've been managing these issues for years.

The body wants to be well. It just needs the right conditions. And that starts with food.

If you'd like to understand more about what might be going on for your individual dog or cat, I'd love to help. Consultations open in January 2027. In the meantime, you can join the waitlist below, or download the free guide to start building your understanding right now.