The centaur diet consists mostly of meat, so they require fewer plants to survive. But plants are very good for their health, preferably root and leafy plants over grains, nuts, and fruits, but they can still enjoy any diet.
Centaurs used to prefer to eat only raw meat and alcohol, but after contact with humans they developed a cooking culture, preferring methods like spit roasts over methods like boiling, but they still enjoy a good stew.
Foods that are toxic or harmful to horses but not to humans are not a problem for centaurs, such as garlic, onions, avocado, chocolate, bread, dairy, and the brassica cultivars.

The upper torsos of centaurs have secondary lungs and a second small heart that help support their brain and make it less likely that they'll faint during heavy activity, with an esophagus leading to the stomach and a thick trachea leading to larger lungs, both on the second torso.
Their esophagus moves food faster than a human esophagus does, so eating something sharp that could scratch their esophagus is more harmful to them, so it's more important for them to really chew their food well. Unlike horses, centaurs can vomit. Their upper torso has none of the other vital organs humans have in that area, leaving more room for muscles, which gives them their massive upper body strength. When a centaur appears to have a belly, there's no interintestinal fat there; it's all abdominal fat.
The lower torso has all other main vital organs, and a larger heart and lungs similar to those of horses, and the thicker trachea allows them to breathe faster. Centaurs often have large nostrils and a slightly elongated face to allow for faster airflow.
Their livers are more similar in function to those of humans and sledge dogs, giving them high endurance. They can run without rest far longer than any other creatures they know.
Their lymphatic and blood system, on the other hand, is more similar to that of horses.
Unlike humans, centaurs do not lose muscle mass due to lack of activity, mostly due to illness or lack of nutrition.

There are some variations depending on what 'taur' is their lower body, but these are the common traits shared among all tauric species.