This is a typical example of a word that can have different meanings given its context. The Dutch language has many of these so called homonyms.
Three translations of "aankomen" are most common, I will illustrate each with an example:
1. to arrive [verb] [kwam aan, aangekomen]
– "De trein zal om 4 uur aankomen."
("The train will arrive at 4 o’clock.")
2. to gain weight
– "Te veel aankomen is slecht voor je gezondheid."
("Gaining too much weight is bad for your health." Note that it is "te veel" and not "teveel". This is one of the most common Dutch spelling errors, due to the fact that "teveel" is actually a word. "Teveel" is a noun and means "surplus".)
3. to touch
For example: you are in a museum and a sign says: "Niet aankomen!" ("Do not touch!")
Read more on homonyms: http://en.wikipedia.org/wiki/Homonym