Simple Gerund vs Active noun

[RohitM269]

I read following sentence in GMAT official Guide:

Doctors generally agree that such factors as cigarette smoking, eating rich foods high in fats, and alcohol consumption not only do damage by themselves but also aggravate genetic predispositions toward certain diseases.

My understanding from MGMAT SC fifth edition is:

"cigarette smoking" is complex Gerund
"eating rich.... fats" is Simple Gerund
"Alcohol consumption" is active noun.

Also, in MGMAT SC it's mentioned that "Simple gerund phrases are NEVER PARALLEL to complex
gerund phrases—even though they both are -ing forms of a verb, and both are used as nouns!"

Where am I getting wrong?

[tim]

You are "getting wrong" [sic] by paying too much attention to technical terms and not enough attention to what makes sense. One of the most harmful things you can do in studying for SC is to concentrate on obscure terms that will keep you from understanding what's really important in the sentences.