Food for sterilised cats: do nutritional needs change?

Myths and truths about sterilisation

“My cat is fat because he’s sterilised, it’s not his fault.” 

While it is true that sterilised cats are more prone to gain weight, it is completely avoidable. Interventions as simple as putting out less food or dedicating some time to playing with the cat every week can produce remarkable improvements in controlling the cat’s weight. Another option is to use cat toys that encourage activity to obtain food.

“He has been hungrier since we sterilised him.”

It is true, sterilised cats seem unable to control how much they eat in the short term. Increased consumption is known to occur immediately after sterilisation, as cats will tend to eat everything placed in their bowls.

“Sterilisation makes cats lazier and changes their personality.”

This is not true. No studies have reported that cats are lazier after sterilisation. However, they do undergo some behavioural changes that are desirable in household cats. On one hand, there is a decrease in sexual behaviours such as territorial urine marking, running away from home, fighting, and so on. On the other, they become much quieter. If physical activity is stimulated with play, sterilised cats will respond by increasing their activity.

Sterilised cats need a smaller energy intake

It has been shown that sterilised cats require less energy, which means that their dietary intake must be reduced to maintain an ideal weight. There are two possible explanations for this:

• Decreased metabolic rate
• Decreased physical activity

As we said above, there may be a suspicion of reduced physical activity due to changes in sexual behaviour and adjustment to indoor life. With respect to metabolic rate, there is no consensus and various studies have produced contrasting results. Some data show a decrease of about 30% in resting metabolic rate, others are more indicative of a change in body composition, which may decrease the cat’s muscle mass, leading to reduced energy expenditure (54% of energy expenditure is related to muscle mass).

Food for sterilised cats: key features for preventing obesity

• Restrict energy intake

Recommendations are to restrict energy by 14–40%. The most widely accepted reference values are 50–60 kcal/kg/day, but it has been reported that under 40 kcal/kg/day is still adequate.

• Prohibit unrestricted access to food

Sterilised cats cannot control their intake.

• More protein, less fat

Improve body composition to lose weight.

• Add indigestible cellulose

This reduces the energy intake.

• Healthy lifestyle

Ideally, dietary interventions should be accompanied by an increase in physical activity. Playing with cats, encouraging them to move around to find food and environmental enhancement are the best ways of encouraging physical activity.