The channel spoke to a man whose brother had converted to Islam and travelled to Syria.
"It began with Youtube videos. He folded his clothes, and went only with long clothing and a short beard," the man said. "He began to read the Quran and would no longer eat pork. He began to concentrate only on religion, and his expression became stricter and stricter."
According to Petter Nesser, a researcher at the Norwegian Defence Research Establishment, converts are often more radical and extreme than ordinary Muslims.
"Various studies show that converts in extreme environments may have more to prove just because they come from outside," he told NRK. "In some cases this means that they are radicalized faster and are more extreme than people who come from a Muslim background."
He said their Western passports, and accent-less grasp of languages, made converts useful for extremist groups.