The IPC cannot officially declare famine - that is usually done by governments or the United Nations.
Reem Tawfiq Khader, 41, a mother of five from Gaza City, said: "The declaration of famine came too late, but it is still important."
"We haven't eaten any protein for five months. My youngest child is four years old - he doesn't know what fruit and vegetables look or taste like."
Rida Hijjeh, 29, said her five-year-old daughter Lamia’s weight had dropped from 19kg (42lbs) to 10.5kg (23lbs). She said Lamia was healthy before the war began and had no prior illnesses.
"This all happened only because of the famine," she said. "There is simply nothing for the child to eat. There are no vegetables, no fruits."
Now, Lamia suffers from swelling in her legs, thinning hair, and nerve problems, she said.
In response to the report, UN aid chief Tom Fletcher said the famine was entirely preventable, saying food could not get through to the Palestinian territory "because of systematic obstruction by Israel".
UN Secretary General Antonio Guterres said: "Just when it seems there are no words left to describe the living hell in Gaza, a new one has been added: 'famine'."
He described it as "not a mystery;" but rather "a man-made disaster, a moral indictment, and a failure of humanity itself".
He added that Israel has "unequivocal obligations under international law - including the duty of ensuring food and medical supplies of the population".
Phillipe Lazzarini, head of the UN agency for Palestinian refugees (Unrwa), said: "This is starvation by design & man-made by the Government of Israel".
UN Human Rights Chief Volker Turk described the famine as "the direct result of actions taken by the Israeli Government", which has "unlawfully restricted" the entry of aid.
UK foreign secretary David Lammy said described the famine as a "moral outrage."
"The Israeli government's refusal to allow sufficient aid into Gaza has caused this man-made catastrophe," he wrote on X.
Israeli Prime Minister Benjamin Netanyahu said in a statement: "Israel does not have a policy of starvation, Israel has a policy of preventing starvation. Since the beginning of the war Israel has enabled 2 million tons of aid to enter the Gaza Strip, over one ton of aid per person."
In recent months, Israel has come under widespread international condemnation for the aid situation in the Gaza Strip.
Last month, after weeks of mounting pressure, the Israeli military said it had airdropped humanitarian aid into Gaza - a move that was criticised at the time by aid agencies as a "grotesque distraction".