Daniel Cormier had to miss his shot at Olympic gold in 2008 when his kidneys failed in Beijing. It nearly killed him. Cormier was cutting weight to compete at 211 lbs.

The symptoms of Acute Renal Failure (ARF) include dry mouth, lack of urine, headache, lower back pain, nausea, and drowsiness. ARF can be treated with fluids and a quick rehydration, but it can also become Chronic Kidney Disease (CKD) if the fighter's kidneys give out from the strain.

"It was very scary," Cormier told USA TODAY Sports. "I was in the hospital. I was getting IV bags, not really eating food. I couldn't recover from the weight cut."

"I had been cutting weight for a really long time. I think I started when I was 13, but I was doing it the wrong way. I put (a plastic sweatsuit) on a week before I weighed in, and I would just start sucking out that water. ... Your body can only take so much. I was beating it down every time. It was very scary."