From the Jerusalem Post:
"We announce the death of the Zionist prisoner, 'Yagev Buchshtav,' 34 years old, as a result of a lack of medicine and food," Hamas claimed in a statement published to their telegram channel on Saturday.Yagev Buchshtav, 34, and his wife, Rimon Kirsht Buchstav, 36, who worked in alternative medicine, were taken hostage from Kibbutz Nirim on October 7. Rimon was released from captivity on November 28, as part of a hostage-prisoner exchange deal between Israel and Hamas.The terrorist organization remarked, "We had previously warned that enemy prisoners are suffering from the same conditions that our people are suffering from."
I have not heard any claims that anyone in Gaza who is healthy and in their 20s or 30s or 40s have died of starvation.
Which means that, assuming Yagev Buchshtav died, he died because Hamas killed him or denied him food altogether.
May Yagev's captors suffer a much worse fate than he seems to have.