Objection 1. It would seem that six daughters are unfittingly assigned to gluttony, to wit, "unseemly joy, scurrility, uncleanness, loquaciousness, and dullness of mind as regards the understanding." For unseemly joy results from every sin, according to Proverbs 2:14, "Who are glad when they have done evil, and rejoice in most wicked things." Likewise dullness of mind is associated with every sin, according to Proverbs 14:22, "They err that work evil." Therefore they are unfittingly reckoned to be daughters of gluttony.
Objection 2. Further, the uncleanness which is particularly the result of gluttony would seem to be connected with vomiting, according to Isaiah 28:8, "All tables were full of vomit and filth." But this seems to be not a sin but a punishment; or even a useful thing that is a matter of counsel, according to Sirach 31:25, "If thou hast been forced to eat much, arise, go out, and vomit; and it shall refresh thee." Therefore it should not be reckoned among the daughters of gluttony.
Objection 3. Further, Isidore (QQ. in Deut. xvi) reckons scurrility as a daughter of lust. Therefore it should not be reckoned among the daughters of gluttony.
On the contrary, Gregory (Moral. xxxi, 45) assigns these daughters to gluttony.
I answer that, As stated above (1 and 2,3), gluttony consists properly in an immoderate pleasure in eating and drinking. Wherefore those vices are reckoned among the daughters of gluttony, which are the results of eating and drinking immoderately. These may be accounted for either on the part of the soul or on the part of the body. on the part of the soul these results are of four kinds. First, as regards the reason, whose keenness is dulled by immoderate meat and drink, and in this respect we reckon as a daughter of gluttony, "dullness of sense in the understanding," on account of the fumes of food disturbing the brain. Even so, on the other hand, abstinence conduces to the penetrating power of wisdom, according to Ecclesiastes 2:3, "I thought in my heart to withdraw my flesh from wine, that I might turn my mind in wisdom." Secondly, as regards the. appetite, which is disordered in many ways by immoderation in eating and drinking, as though reason were fast asleep at the helm, and in this respect "unseemly joy" is reckoned, because all the other inordinate passions are directed to joy or sorrow, as stated in Ethic. ii, 5. To this we must refer the saying of 3 Esdra 3:20, that "wine... gives every one a confident and joyful mind." Thirdly, as regards inordinate words, and thus we have "loquaciousness," because as Gregory says (Pastor. iii, 19), "unless gluttons were carried away by immoderate speech, that rich man who is stated to have feasted sumptuously every day would not have been so tortured in his tongue." Fourthly, as regards inordinate action, and in this way we have "scurrility," i.e. a kind of levity resulting from lack of reason, which is unable not only to bridle the speech, but also to restrain outward behavior. Hence a gloss on Ephesians 5:4, "Or foolish talking or scurrility," says that "fools call this geniality--i.e. jocularity, because it is wont to raise a laugh." Both of these, however, may be referred to the words which may happen to be sinful, either by reason of excess which belongs to "loquaciousness," or by reason of unbecomingness, which belongs to "scurrility."
On the part of the body, mention is made of "uncleanness," which may refer either to the inordinate emission of any kind of superfluities, or especially to the emission of the semen. Hence a gloss on Ephesians 5:3, "But fornication and all uncleanness," says: "That is, any kind of incontinence that has reference to lust."
Reply to Objection 1. Joy in the act or end of sin results from every sin, especially the sin that proceeds from habit, but the random riotous joy which is described as "unseemly" arises chiefly from immoderate partaking of meat or drink. On like manner, we reply that dullness of sense as regards matters of choice is common to all sin, whereas dullness of sense in speculative matters arises chiefly from gluttony, for the reason given above.
Reply to Objection 2. Although it does one good to vomit after eating too much, yet it is sinful to expose oneself to its necessity by immoderate meat or drink. However, it is no sin to procure vomiting as a remedy for sickness if the physician prescribes it.
Reply to Objection 3. Scurrility proceeds from the act of gluttony, and not from the lustful act, but from the lustful will: wherefore it may be referred to either vice.
Source: Summa Theologica (New Advent)