Although Audrey Hepburn has always been held up as a model of thinness, her son reveals that the root of her thin physique was her extreme malnourishment during the war.

“The reason for her slenderness was because from the time she was 9 to 16, during World War II, she was extremely malnourished,” says her youngest son Luca Dotti who’s written a new memoir about his mom, Audrey at Home.”The time she most needed nourishment, she didn’t have enough food.”

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“When the Nazis locked down Holland in 1944, they called it the Winter of Hunger and my mom didn’t have enough to eat,” he says. “Almost to the point of her body failing.”

At the end of the war, Hepburn, who stood 5’6″, weighed just 88 lbs. The actress later described those years: “We ate nettles and everyone tried to boil grass – in addition to tulips – but I really couldn’t stand it.”

One of the few things they could eat during the war years was endive. “For a long time that’s all there was,” writes Luca. “She used to say, ‘Thank God there was at least that,’ but then she would imitate Scarlett O’Hara in Gone with the Wind, saying, ‘I swore to myself that I would never eat it again in my life, not ever.’ ”

At times, Hepburn’s mother told her to “drink water to feel full.” And when she was too weak to stand up, he writes, “She would spend entire days in bed with a book, thus hoping to expel from her mind obsessive thoughts about food.”

“She suffered from asthma, jaundice and other illnesses caused by malnutrition,” writes her son, “including acute anemia and a serious form of edema which Mum explained like this: ‘It begins with your feet and when it reaches your heart, you die. With me, it was above the ankles when I was liberated.’ ”

One day toward the end of the war, a Dutch soldier gave her seven candy bars, which she immediately gobbled up along with condensed milk given out by the U.N., and she immediately became ill. “The liberation forces came in with all sorts of things, cigarettes and chocolate, and my mother hadn’t eaten for months,” recalls Luca. “She ate it up but her stomach wasn’t prepared. It was too small. She couldn’t keep it down. Her stomach had been empty for too long.”

Throughout her entire life, Hepburn carried the pain of the war and all she had seen. “Still, the taste of chocolate for her was connected with liberation,” says her son. “It was the real taste of freedom.”