The 80/20 percentage refers to the proportion of fat and protein in the grind – not the proportion of calories. According to CookingLight, 20% of fat by weight contributes 72% of the total calories in a 3.5 ounce portion of raw ground beef! That means about 180 calories of the 250 total calories come from fat. The Dietary Guidelines for Americans recommends 20 – 35 percent of total calories from fat, or less than 30% calories from fat per meal.
Look for 90/10, 95/5, or better yet, purchase a lean whole cut of meat, like sirloin or brisket, trim it up, and grind it yourself. If you don’t have a meat grinder (and okay, a lot of people don’t), ask your butcher to do it for you. It’s fresher, leaner, and you don’t need to worry about nasty additives lurking in ground beef.