Donna Erie is a classic yo-yo dieter. In the last four years, she lost 60 pounds on a liquid diet, 35 pounds with a combination of herbal weight-loss pills and four hours of daily exercise and 15 pounds on the Atkins plan.
Each time, however, she put the weight back on.
"I've been dieting forever," says the 51-year-old secretary for the city of Los Angeles.
Carrying 210 pounds on her 5-foot, 7-inch frame, Erie's aware of studies showing that weight reduction decreases the risks of diabetes and other illnesses. She's determined to slim down to thwart the diabetes that both her parents developed.
But diet and nutrition experts are concerned about the potential health consequences for people, like Erie, who repeatedly lose and regain pounds.
Nutrition educators at UC Berkeley recently reported that women who began dieting before age 14 were not only heavier but also were more than twice as likely to have dieted more than 20 times than women who began restricting their calories later. Lead author Joanne Ikeda said those who begin this pattern of losing and regaining pounds before puberty could disrupt their physical development.
Now, there's new evidence that yo-yo dieting may weaken the immune system.
Researchers at the Fred Hutchinson Cancer Research Center in Seattle measured the effectiveness of natural killer cells, which attack viruses and cancers, in a study of 114 obese, sedentary women ages 50 to 75. Each woman was asked how many times she had taken off at least 10 pounds in the previous two decades.
Among women who had lost weight at least five times, natural killer cell function dropped 30%, the researchers reported. The immune cells are part of the body's complex defense against illness and infection.
Scientists aren't sure how much disease-fighting power must be lost to create harm, said lead researcher Erin D. Shade, a nutritionist. However, she said, a crucial finding was that the immune system effects persisted as many as 15 years after women had last dieted.
At a time when an estimated 50% of American women and 25% of American men are either dieting or thinking about dieting, such findings reinforce the wisdom of sticking with a sustainable weight. They underscore the need for more research into yo-yo dieting, which has become a lifestyle for many people.
"Weight cycling has been somewhat neglected by the research community," said Cornelia Ulrich, a research epidemiologist and senior author of the immune system study.
