Carbohydrates are non-essential nutrients for dogs and cats: animals can obtain them from the diet but they can also synthesize glucose, the sugar that serves as fuel to perform most body functions, from proteins and fats, in a process called gluconeogenesis. However, the fact that carbohydrates are not indispensable does not imply that they are unsuitable for the nutrition of dogs and cats or that they cannot be used by these animals. Dogs are classified as omnivorous animals. In fact, it has been shown that the acquisition of the ability to digest diets rich in starch was a key aspect in the domestication of these animals from their ancestor, the wolf (Axelsson et al., 2013). Regarding cats, although they are considered carnivorous animals since they need to acquire certain essential nutrients from foods of animal origin (i.e. taurine, arginine, vitamin A, vitamin B3), they are also able to digest and efficiently use carbohydrates (De-Oliveira et al., 2008). Thus, a moderate intake of carbohydrates in the diet of dogs and cats is beneficial since it allows more efficient use of proteins because the animals do not have to devote a part of the protein they consume to obtaining energy.
There is a belief that eating a carbohydrate-rich diet can lead to long-term obesity or diabetes, especially in cats. However, there is currently no scientific evidence to support this. Obesity occurs when an animal ingests more calories than it uses, regardless of what nutrients those calories come from (carbohydrates, proteins, or fats). Regarding diabetes, some studies have confirmed that, in healthy cats, there is no negative effect of high carbohydrate intake on blood glucose concentration and insulin sensitivity (Thiess et al., 2004). What has been shown is that low-carbohydrate diets can be beneficial in cats that have previously developed diabetes, improving glycaemic control and reducing the need for exogenous insulin (Bennett et al., 2006).
