Flank is the leanest then skirt,flank, and tenderloin. These are all considered lean cuts of of beef.
Chuck is one of the fattiest cuts on a cow.
Flank is 4.5 grams of fat and 160 cals per 100g eaten.
Skirt is 15.1 grams and 250 cals. Hanger and filet are about the same.
Chuck is 25.6 grams of fat and 330 cals.