I've heard eating burnt food like this can increase the risk of cancer.中eat为啥加ing?

比如说：Eating burnt food isnotgood.Eating burnt food is not good.因为不管是主语还是宾语，都属于名词。而eat是动词，怎么当名词用？当然是变成“动名词”。动名词就是动词加上ing.而Eating burnt food like this can increase the risk of cancer.这句话是宾语从句，Eating在这个宾语从句中作为主语。我可以肯定地说我是对的，这是一个复合句式，用hear doing是解释不通的。