Having a good diet is of great importance to keeping healty.为什么要用keeping .to不是要跟原型吗?

Having a good diet is of great importance to keeping healty.
为什么要用keeping .to不是要跟原型吗?

举个例子：
The news is of great importance to the family.
这里"family"是名词,可见词组"be of great importance to“ 后应加名词,故用动词的现在分词形式"keeping..."