"Leviticus 3:14-16 And he shall offer thereof his offering, even an offering made by fire unto the LORD; the fat that covereth the inwards, and all the fat that is upon the inwards, And the two kidneys, and the fat that is upon them, which is by the flanks, and the caul above the liver, with the kidneys, it shall he take away. And the priest shall burn them upon the altar: it is the food of the offering made by fire for a sweet savour: all the fat is the LORD’S."
"Biologically, the fat is used by the body to store excess energy in good times for hard times; let us make an analogy; fat is the “money” your body needs to survive. When there is a temporary excess of money coming in, on payday or harvest season, you will first spend that money on this week’s grocery bill, and then you will store the surplus in a bank. Then in the downtime between your next payday you will draw on that reserve. If you have a well paying job or low expenses, then you will continue to have an excess every month and save that money back for your retirement, children, and grandchildren."
https://www.thesimpleanswers.com/articles/2007/12/09/why-is-the-fat-reserved-for-god/