Doctors generally agree that such factors as cigarette smoking, eating

Generally, whenever a noun form exists for an action , that noun form is preferred to the -ing form of that action.

Here, alcohol consumption is preferred over consuming of alcohol

Coming to the parallelism aspect , the parallelism rules say the following are parallel
1) action nouns || to action nouns ( consumption here)
2) nouns || to complex gerunds (verb-ing OF <something>) --> notice the presence of "of <something>"
2) verb-ing (simple gerund) || to verb-ing (simple gerund)

Going by the rule - I see what you're saying. it's difficult to explain the parallelism by these rules.
But, going by the construction of this sentence, it is clear to see that smoking , eating and consumption are all unambiguously positioned as nouns . (considering verb-ing can be modifiers as well) ,

so I am guessing GMAC took the liberty to position all the nouns parallel (smoking, eating, and consumption) to avoid the awkwardness of a construction like below.

smoking of cigarettes, eating of rich foods high in fats, and alcohol consumption

this might be the only other possible construction to fit the rule, because smoking and eating do not have a proper noun form.

my takeaway would be that we should keep an eye on the role of verb-ing and if it's unambiguously a noun, it can be presented parallel to action nouns. just noticed that this question is repeated in OG16 (Q87) , verbatim, without eliminating the question. so GMAC believes this a valid construction. the rule is probably hard for modifier forms and soft on noun forms .

A new learning today, after having recently learnt about how past participle forms can be parallel to present participle forms - from the famous fungus question .
thanks for asking this Q. do drop in another post if you notice similar construction in other Qs.