My cat

My cat is 16 and he keeps throwing up after he eats, what could this mean?

Could suggest lots of things, including:

Eating too much too quickly

A sign of eating something poisonous

An intolerance to a food

Pancreatitis

Sounds like a vet trip is needed! It is important to get help fairly quickly as if cats are not taking in sufficient amounts of food they can develop liver problems fairly quickly.

Can you give us some more details, how long has this been happening? Has he lost weight recently? Have you changed his food? Is he opening his bowels normally? Has he eaten something he shouldn't?

Since he likes to eat the kitten food we switched him to that and its been going on like a year.

Maybe it's a bit rich for him? Perhaps try going back to what he was eating before he was vomiting. I would still get him checked over by the vet though, especially since he is an old man in cat years!

My friend said hes 80 in cat years, even on that food he would get sick, my mom said hes just getting old so theres nothing to do.

It is not true that old age in cats will automatically cause them to throw up.  I have a 16 year old cat, and she does not throw up very often.  Something is not right. 

He needs to be seen by a Vet to try to determine what the cause is.  As Evamilly said, it could a variety of things.  The problem with prolonged vomiting too is, it can cause damage to the esophagus, so you definitely want get this nipped in the bud.  Poor baby.  A year!  This is way too long!

You  need to determine how soon after the meals this occurs, whether or not the food seems digested or not, whether it's ALL meals or just some, whether it's with certain foods, or ALL foods,and exactly what those foods are, and present that data to your Vet.  Then they can try to figure out what is causing it.