Every cook knows about grill shrinkage—the tendency of burgers to lose juice and fat as they approach perfection. But we wondered: Do fattier cuts lose a higher percentage of their fat over heat, since fat melts and combusts easily? And if so, does a fattier grind of beef—say, the usually cheaper 80/20—end up close to the 90/10 grind that we usually recommend?

To find out, we sent samples, raw and grilled, to the lab for analysis. From the raw samples, we wanted to know if the fat-ratio labels were even accurate. The answer there was "sort of." All grinds had slightly less fat than labeled; our 90/10 was actually 93/7. From the grilled samples, we wanted to know: How much gets lost over a fire? See answers below.

80/20 fattiest grindRaw (4 ounces): 21.2g total fat, 9g sat fatGrilled (2.6 ounces): 14.2g total fat, 6.1g sat fatShrinkage: 34% weight loss, 33% fat loss

This grade indeed lost the most fat, but the resulting burger was still left with almost double the fat of the leanest grind.

85/15Raw (4 ounces): 16.8g total fat, 6.9g sat fatGrilled (2.7 ounces): 12.4g total fat, 5.1g sat fatShrinkage: 33% weight loss (wow!), 26% fat loss

90/10 leanest grindRaw (4 ounces): 8.3g total fat, 3.5g sat fatGrilled (3.1 ounces): 7.5g total fat, 3.2g sat fatShrinkage: 22% weight loss, 10% fat loss

* Still our recommended grade—just as tasty but with much less fat. Less shrinkage, too.What the Ratios Mean: The ratio is percentage by weight. Fat is higher in calories than protein, so a 4-ounce raw 80/20 beef patty has 285 calories, versus a 90/10 patty, which has 200 calories. And the 90/10 has 12.9 fewer grams of total fat.

Photo: Francesco Tonelli/Philippa Brathwaite