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  • The Links Between Your Pet’s Diet & Behaviour

    The Links Between Your Pet’s Diet & Behaviour

    It is well known that the food your pet eats can have an effect on their physical health. A high-quality diet can have many benefits, including promoting healthy coats and joints, improving dental health, and aiding in the protection of vital organs. However, it is less commonly acknowledged that diet can also play a vital role in your pet’s behaviour. The quality and quantity of protein in a diet, as well as the presence of certain amounts of carbohydrates, can all alter chemical functions in the body that are then expressed by your dog or cat as certain behaviours.

    When reading further into this subject online, it becomes obvious that there is an abundance of conflicting information available. Vets, behaviourists, trainers, breeders, and pet owners all seem to offer differing opinions on what affects a pet’s behaviour and what is best for them in terms of diet. By looking at scientific studies we have been able to separate the facts from the myths and gain a better understanding of how nutrition can affect your pet’s behaviour.


    Carbohydrates are a common ingredient in pet foods, usually seen in the ingredients list as types of rice, potato or cereals. Being carnivores, dogs’ and cats’ main source of energy should ideally not come from carbohydrates but instead comes from protein and fats. Therefore, if your pet is fed a diet where carbohydrates are the main energy source, it may cause your pet to act differently than if it were fed an alternative diet.

    When fed a diet high in carbohydrates, one study showed that dogs became less active. It was hypothesised that this was due to the dogs being more relaxed and more satiated as a result of their diet1. However, behaviour analysis could not verify this as there was no recorded behavioural difference between the dogs fed a high carbohydrate diet and those fed a low carbohydrate diet.

    Another study by the same author confirmed that high levels of carbohydrates caused a decrease in activity in dogs. In this study, it was stated that this lack of activity was due to the fact that carbohydrates require a longer digestion time than protein, and therefore did not provide an efficient enough source of energy2.

    By analysing the way dogs store and utilise energy from different sources, it can be confirmed that there is little benefit in providing dogs with a carbohydrate-rich diet. Carbohydrates do not provide enough energy for an active dog3, and as a result, dogs fed this kind of diet may show lower energy levels and tiredness. They may also appear calmer, however, there is no evidence to confirm that this is due to chemical functions in the brain and not a side effect of fatigue.

    In regards to cats, studies have linked a high carbohydrate diet to decreased physical activity4. Much like in dogs, cats derive little energy from carbohydrates and instead rely on protein as an efficient energy source5. Therefore, it can be assumed that cats will react in a similar way to dogs as mentioned above when fed a carbohydrate based diet. Lethargic behaviour in cats can swiftly result in weight gain and obesity if not managed.


    While it is accepted that cats thrive on high levels of digestible protein, some opinions state that feeding dogs a high protein diet can lead to aggression and hyperactivity. However, there are no scientific studies that prove this to be the case. It appears that many studies stating that high protein diets result in aggression are undertaken with the supplementation of tryptophan6,7

    Tryptophan is an essential amino acid that is found in protein-based foods and is used to synthesise protein in the body. High levels of tryptophan have been found to increase aggression in rats and primates when administered in the form of a supplement, however, when naturally occurring in the diet in the form of protein, it reduces aggression and other harmful behaviours8.

    There is little evidence to suggest that being fed a diet containing naturally occurring tryptophan will cause aggression, and some studies seem to suggest the opposite. One study was conducted in a stressful shelter environment with rescue dogs. The dogs were fed a diet high in protein and fat, and with high quality animal ingredients such as fresh meat as opposed to meat meal. Over time the dogs were observed to be less agitated and distressed by the kennel environment, and by the end of the study, the overall behaviour of the dogs had improved9.

    In regards to hyperactivity, protein is actively utilised in both dogs and cats as a source of energy and aids in gluconeogenesis, a reaction in the body that helps maintain healthy blood sugar levels and energy10. This process does not create large amounts of energy, and therefore could not be responsible for hyperactive behaviour.

    Being obligate carnivores, cats have an increased need for protein compared to dogs. This is confirmed by the efficiency in which cats convert protein to useable energy11. As well as providing your cat with a healthy source of energy, protein-rich foods are more nutrient dense, and therefore should satiated hunger for longer.

    Your cat’s motivation to play and hunt is influenced by their level of hunger12.  A hungry cat is more likely to seek out live prey, whereas a satiated cat will be less likely to hunt. Cats are less satiated when fed high carbohydrate diets compared to high protein diets, so may be more likely to seek out alternative food sources13. Therefore, providing a diet containing high levels of digestible protein may actually decrease unwanted hunting behaviour in outdoor cats.

    Providing a diet suitable for your pet’s needs is vital for their physical and mental health, and unfortunately, there is a lot of conflicting information about what is considered to be the best. All pets have their own unique personalities and behaviours, so this should always be taken into account if considering the impact your pet’s diet is having on their behaviour. As mentioned above, signs of aggression and hyperactivity are most likely not linked to diet, but instead may be linked to a need to increase mental and physical stimulation, or due to an underlying illness.

    If you are unsure about your pet’s dietary needs, our team at Thoughtful Pets will be happy to provide you with unbiased nutritional advice.

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