Still, Cooper accepted the fight after taking 30-percent of Dern's purse as punishment.
Dern hit the scale at 123 pounds, well over the 116 pound limit for a non-title, strawweight bout.
Mackenzie Dern still has plenty of questions left to answer after coming into her fight seven pounds overweight, but there's no denying her performance after making quick work of Amanda Cooper on Saturday night in Brazil.
Cooper won her last fight in her hometown of Detroit, knocking out Angela Magana at UFC 218.
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She made weight prior to her split decision victory over Ashley Yoder in her UFC debut in March.
The 26-year-old Cooper has a career record of 4-3. Later that morning, all fighters make weight except for Mackenzie Dern.
Well, more recently, Cooper tweeted out the comment below.
UFC 224 takes place at Jeunesse Arena in Rio de Janeiro, and the main card airs on pay-per-view following preliminary-card bouts on FX and UFC Fight Pass. The weigh-in drama then led to a very motivated Cooper, who seemed to be looking for some revenge on Dern. Swarming in, Dern was able to get full mount before landing a barrage of elbows and strikes.