Ötzi the iceman filled his belly with fat before he set out on the ill-fated hunting trip that ended with his bloody death on a glacier in the eastern Alps 5,300 years ago, scientists say.

The first in-depth analysis of the hunter’s stomach contents reveal that half of his last meal consisted of animal fat, primarily from a wild goat species known as the Alpine ibex.

While researchers have previously studied remnants of food in Ötzi’s intestines, a more complete picture of his final feast was delayed because they could not find his stomach. It was finally located by a CT scan, tucked up under his ribcage near his shrunken lungs.

“It was surprising to see this extraordinarily high-fat diet,” said Frank Maixner at the Eurac Research Institute for Mummy Studies in Bolzano, Italy. “He clearly knew that fat is a high-energy source and he really composed his diet to survive at high altitude.”

Ötzi’s last meal may have fortified him for a hunting trip that lasted several days high up in the Alps, but it may not have been the most enjoyable feast. Maixner has tried ibex. He said the meat is not too bad, but struggled to find the words to encapsulate the experience of eating the animal’s subcutaneous fat. “The taste is really, well, it’s horrible,” he said. “And they had no salt at the time.”

Facebook Twitter Pinterest A: Ötzi and the contents of his stomach. B: Meat fibres from his stomach. C: Plant remains. Photograph: Frank Maixner/Eurac Research/Institute for Mummy Studies

German tourists discovered the copper-age corpse in 1991 while hiking at 3,200 metres in the Ötztal Alps near the Austrian-Italian border. They thought the body, soon nicknamed Ötzi, was that of a modern mountaineer, but upon excavation the well-preserved remains were found to be more than 5,000 years old. The hunter, thought to be 45 years old when he died, was clad in a woven grass coat and wore leggings and shoes of leather. He was covered in simple line tattoos, and carried a copper axe, a knife and flint-tipped arrows.

Ötzi’s body is stored at -6C to ensure the remains do not deteriorate. So to analyse his stomach contents, Maixner, part of an international team of scientists, had to partially thaw the corpse to collect samples to check for remains of his final meal.

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Through a combination of methods including DNA matching and microscopic inspections, the researchers found traces of red deer and ibex meat, ancient wheat and plenty of ibex fat. They also discovered multiple traces of toxic bracken, a finding that has the scientists stumped.

Writing in the journal Current Biology, the researchers speculate that Ötzi may have eaten the toxic bracken to rid himself of whipworm parasites, which had been discovered in his intestines previously. But Maixner favours other explanations. Ötzi may have eaten the bracken as a food supplement, a practice known among some indigenous groups. “Another possibility is that he wrapped his dried meat in bracken leaves and some of the material got into his gut unintentionally,” Maixner said.

However it got there, the toxic plant was not fatal. The discovery in 2001 that an arrowhead had shattered Ötzi’s shoulder blade suggests that events turned dark on the mountain that day. “The current thinking is that he bled out and died on the glacier,” said Maixner.