Kittens grow rapidly in their first year, and their diet plays a major role in helping them develop strong bones, healthy muscles, and a resilient immune system.

But as they mature into adult cats, their metabolism slows, and their nutritional needs change. Feeding kitten food for too long can lead to health issues like obesity. Here’s when and how to make the switch, with guidance from ROYAL CANIN®️.

Why kitten nutrition is so important

Kittens require a diet that is:

High in energy

Rich in highly digestible protein

Full of vitamins and minerals

Formulated with immune-supporting nutrients

ROYAL CANIN®️ kitten diets are tailored for these needs, supporting everything from immune development to digestive health and bone growth.

Kitten growth stages

Birth to 4 months: A period of intense growth. Kittens need calorie-dense food to support physical development and immunity.

4 to 12 months: Growth slows slightly, but they still need a high-quality, easy-to-digest diet. At this stage, they’re building strength and starting to approach adult size.

Note: Maine Coons and other large breeds may continue growing until 15 months, and benefit from extended time on kitten food.

When to switch to adult food

Most cats: around 10–12 months

Large breeds (e.g. Maine Coon): up to 15 months

Once your cat has reached around 90% of their adult size, it’s time to transition to an adult diet.

Why it matters

Kitten food contains more calories to fuel growth. Adult cats, however, need fewer calories per kilogram of body weight due to slower metabolism and lower activity levels.

Continuing with kitten food into adulthood can lead to weight gain and increase the risk of diabetes, arthritis, and other health issues.

With around 60% of cats considered overweight or obese, it’s essential to feed age-appropriate food and follow correct portion guidelines.