AT 5 FEET 3 AND 100 pounds, she wasn't truly emaciated, but everyone at the Boston Ballet had watched Heidi Guenther struggle a bit too successfully with the pressure to stay thin. ""Please do not lose any more weight,'' company officials had urged the 22-year-old dancer in a written evaluation in January. On June 30, Guenther died suddenly of apparent heart failure. What prompted her collapse during a California car trip is still unclear - a preliminaryautopsy found no apparent problem with her heart. But the ballet company speculated last week that the death may have been ""precipitated by an eating disorder.''
Two years ago, when Guenther was working her way into the Boston Ballet's main company, an assistant artistic director advised her to lose five pounds. She did, and the company promoted her. But Guenther continued to lose weight. Eating problems are common among professional ballet dancers. ""Some go through years of starving and laxatives and diuretics,'' says Dance magazine columnist Linda Hamilton. Still, anorec-tics typically grow weak and lethargic, and acquaintances say Guenther was always strong and exuberant. Though she was thin, being 15 pounds underweight is rarely life-threatening. The cause of Guenther's death is still under investigation, but it may remain a tragic mystery.