What figures of speech are used in the following article?...

Your question is about an articled titled "Science and
Pseudoscience in Adult Nutrition Research and Practice."  Since this is clearly a
non-fiction article on a technical subject, one would not expect it to use much
figurative language.  Still, there are some
examples.

METAPHOR: a comparison that does not use "like"
or "as"

a) "nutrition research...have lagged behind many
other...fields."

Only a person (or animal, or
vehicle) in a race can lag behind; saying that one kind of research
"lags behind" another is a
metaphor.

b) "such
studies...are...the result of
'data-dredging."

The author is comparing some
studies to "dredging," which is the process of cleaning a body of water by dragging up
the mud and sewage that is clogging it.  The author is saying that some researchers find
a lot of "dirty," unreliable statistics, "draw" them out of the mud, and use them as the
basis for their conclusions.

ALLUSION: a
reference to another work of literature, or to history,
etc.

a) "Are there 'fountain of youth' nutritional
approaches...?"

The "Fountain of Youth" is a
reference to ancient legend (see link below)

b) The author refers
several times to the ancient Greek philosopher, Aristotle.