Hello in Jeremiah 9:23 it says
23 Thus saith the Lord, Let not the wise man glory in his wisdom, neither let the mighty man glory in his might, let not the rich man glory in his riched.
My question is wouldn’t weight lifting with purpose to improve physical looks/to obtain More muscular body by in same category as a form of unrighteous boasting? But then it would seem that any kinda change in our appearance with purpose to look better could be categorized as boasting which wouldn’t seem to be prohibited.
You are bringing up an intersecting point, and I can add to your point that according to what you are asking, it would be a sin for a person to work to try to make himself richer than he is, if he already has his needs, because it would be a form of boasting. But lets look at the whole verse. The verse says ” Let the wise man not praise himself for his wisdom, and the strong man with his strength, and the rich man with his fortune. But with this should a person praise himself, by his knowledge of Me, because I am G-d who does kindness justice, and charity in the land, and in this person I have desire says G-d”. The meaning of these verses is that it is wrong for a person to praise himself for things that are futile and temporary, such as physical strength, wealth or wisdom. Besides that these are tings controlled by G-d and He gives them according to His will, and can be taken away as soon as He wishes. Therefore it is incorrect for a person to boast about things that are not inherently his. On the other hand acquiring knowledge of G-d and achieving a closeness to Him, is something that will stay with the person for eternity, therefore this is something that is really praiseworthy.
Having said that, it is wrong for a person to be boastful, and haughty, whether it is about looks, money or anything else.