A 500g package of Coles regular mince has approximately 20g protein per 100g serve, for 230 calories, with 17g of fat:
However, the same brand, same weight of extra lean mince has 21g of protein oer 100g serve, basically the same amount, but with 5g of fat for 133 calories: https://shop.coles.com.au/a/national/product/coles-beef-lean-5-star-mince?uztq=46abcbb7e16253b0cdc3e6c5bbe6a3f0&cid=col_cpc_Generic%7CColesSupermarkets%7CPLA%7CMeat&Seafood%7CAustralia%7CBroad&s_kwcid=AL!12693!3!495628917070!!!u!364576380634!&gclid=Cj0KCQiAweaNBhDEARIsAJ5hwbei6dV_IZvojWbW0vlwsMjM7Ail1WxVqTGnuYSZwYBSnhJG2UjWViQaAnqaEALw_wcB&gclsrc=aw.ds
My question is, what is making up the extra weight? Less fat, same protein, same weight? Did they just add indigestible sawdust to bulk up the weight without increasing the calories?
Leaner meat has a higher water content.
See the nutrition info the from the USDA food database:
80/20 ground beef is 61.9% water
85/15 ground beef is 65.7% water
90/10 ground beef is 69.4% water
95/5 ground beef is 73.2% water
This is because fat cells (i.e. adipocytes) have a lower fraction of water compared to other cell types, due to the fact that most of their volume is taken up by a lipid-filled vacuole.