That is in regards to the word "bowels."
You are conflating 'bowels' with 'stomach' which are two Greek words. The Philippians 3 verse is about the stomach.
Verses that refer to σπλάγχνα translated literally “bowels”
Verses that use σπλάγχνον, which can literally be translated as 'bowels', some non-literal examples.
2 Corinthians 6:12
Greek: τοῖς σπλάγχνοις ὑμῶν
KJV: “ye are straitened in your own bowels.”
Philippians 1:8
Greek: ἐν σπλάγχνοις Χριστοῦ Ἰησοῦ
KJV: “in the bowels of Jesus Christ.”
Philippians 2:1
Greek: εἴ τις σπλάγχνα καὶ οἰκτιρμοί
KJV: “if any bowels and mercies.”
Colossians 3:12
Greek: σπλάγχνα οἰκτιρμοῦ
KJV: “bowels of mercies.”
Philemon 7
Greek: τὰ σπλάγχνα τῶν ἁγίων
KJV: “the bowels of the saints.”
Philemon 12
Greek: τὰ ἐμὰ σπλάγχνα
KJV: “mine own bowels.”
Philemon 20
Greek: τὰ σπλάγχνα μου
KJV: “refresh my bowels in the Lord.”
1 John 3:17
Greek: κλείσῃ τὰ σπλάγχνα αὐτοῦ
KJV: “shutteth up his bowels [of compassion].”
Verses that refer to κοιλία, literally translated “belly / stomach”, certain examples.
John 7:38
Greek: ἐκ τῆς κοιλίας αὐτοῦ
KJV: “out of his belly shall flow rivers of living water.”
Romans 16:18
Greek: τῇ ἑαυτῶν κοιλίᾳ
KJV: “they… serve… their own belly.”
Philippians 3:19
Greek: ἡ κοιλία
KJV: “whose God is their belly.”
We have also have another similar scripture in the context of fornication.
I Corinthians 6
12 All things are lawful unto me, but all things are not expedient: all things are lawful for me, but I will not be brought under the power of any.
13
Meats for the belly, and the belly for meats: but God shall destroy both it and them. Now the body is not for fornication, but for the Lord; and the Lord for the body.
14 And God hath both raised up the Lord, and will also raise up us by his own power.
15 Know ye not that your bodies are the members of Christ? shall I then take the members of Christ, and make them the members of an harlot? God forbid.
16 What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh.
17 But he that is joined unto the Lord is one spirit.
18 Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body.
Tertullian of Carthage from the 2nd century commented on the Philippians passage:
" For it is emulation, not religion, which impels them. Sometimes it is that god- their belly. Not one of such women knows how to speak of the good of single-husband hood; for their "god "as the apostle says, "is their belly; "
A quote from Greek-speaker John Chrysostom from the early 400s:
"Your belly is given to you so that you may nourish it, not so that it may burst. Your body is given you that you may rule it, not so that you may have it as a mistress. It is given that it may serve you for the nourishment of the other members, not so that you may serve it. Do not exceed these bounds. The sea in flood does not so much harm to the boundaries as our belly does to our bodies and our souls. The flood overwhelms only part of the land. The god of the belly overwhelms the whole body. Set selfconstraint as a bound to it as God sets the sand to the sea."
Some commentators think Paul may have been referring to pleasure-seeking ideologies of Epicureans.
Athenaeus, Deipnosophists, XII p. 546F:
Epicurus says, "The principle and the root of all good is the pleasure of the stomach; even wisdom and culture must be referred to this."
This is from the classical era. While he may have used 'gaster', Paul's readers may have made the connection.