Sins of the reproductive system are given two whole chapters in Leviticus (Chs. 18 and 20) and mentioned numerous times elsewhere in the Bible. The lack of any similar exposition about gluttony should prove - if the Bible is your basis of morality - that the former are worse.
Matthew 12:31-32
31Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men.
32And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come.
Leviticus spills a lot of ink on the questions of what foods are permissable to eat and the dietary laws are a significant part of the Jewish law in general. Violations of these laws are sins of the digestive system and were certainly important to the G-d that handeed down the ten commandments. A glutton is a persistant and, apparently, unrepentant sinner if he or she keeps the excess weight. It is not a matter for conjecture, the evidence is right there for all to see.