For most of her childhood, Jenna (not her real name) spent dinnertime staring at a plate of food that she refused to touch. She often was sent to bed hungry, or her parents caved and let her eat the only thing she could get down: French fries. Dinnertime hasn’t changed much for the 30-year-old dance teacher, who estimates that fries still constitute 90 percent of her meals. In the last 15 years, the only addition to Jenna’s diet has been pancakes, which she says took more than a year to work up the courage to taste. When she tried an orange for the first time at age 18, she immediately threw up.