A man who went missing in western Japan survived in near-freezing weather without food and water for over three weeks by falling into a state similar to hibernation, doctors said.

Mitsutaka Uchikoshi had almost no pulse, his organs had all but shut down and his body temperature was 71 degrees Fahrenheit when he was discovered on Rokko mountain in late October, said doctors who treated him at the nearby Kobe City General Hospital. He had been missing for 24 days.

"On the second day, the sun was out, I was in a field, and I felt very comfortable. That's my last memory," Uchikoshi, 35, told reporters Tuesday before returning home from hospital. "I must have fallen asleep after that."

Doctors believe Uchikoshi, a city official from neighboring Nishinomiya who was visiting the mountain for a barbecue party, tripped and later lost consciousness in a remote mountainous area.

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His body temperature soon plunged as he lay in 50-degree weather, greatly slowing down his metabolism.

"(Uchikoshi) fell into a state similar to hibernation and many of his organs slowed, but his brain was protected," said Dr. Shinichi Sato, head of the hospital's emergency unit. "I believe his brain capacity has recovered 100 percent."

Uchikoshi was treated for severe hypothermia, multiple organ failure and blood loss from his fall, but was unlikely to experience any lasting ill effects, Sato said.

Doctors were still uncertain how exactly Uchikoshi survived for weeks with his metabolism almost at a standstill.

In animals like squirrels or bears, hibernation reduces the amount of oxygen that cells need to survive, protecting them from damage to the brain and other organs.