2. Because the fat content in lean beef is extremely low, only a few grams, on the contrary, its protein content is very high, about 20 grams. Generally, most of the energy consumed by eating lean beef is in the form of protein, and protein won't make us fat. However, fat cows contain a lot of fat, which will lead to excessive fat intake, so it is not recommended to eat fat cows to lose weight and eat lean beef.