The cost of overweight to the economy is NIS 6 billion a year, or 1.2 percent of the gross domestic product and 15% of national expenditures on health, according to research that will be presented during the two-day annual conference of the National Institute for Health Policy Research (NIHPR) that will open near Safed on Wednesday. Just a small increase in the percentage of Israelis exercising regularly could save hundreds of millions of shekels in medical expenses and prevent hundreds of deaths a year, the research shows. Meanwhile, a separate study has found that although nearly a third of Israeli women are currently on a weight-loss diet, 18% of those have a normal body mass index and their diets are therefore unnecessary. These data were reported Tuesday from a Shiluv Research Institute poll conducted for the Israel Center for Bariatric Surgery at Tel Aviv's Assuta Medical Center. The survey showed that 34% of women aged 18 to 29, 28% of those aged 30 to 49 and 32% among those who are 50 and older are dieting. Assuta doctors said the actual rate of those dieting is probably higher, because there is a natural tendency not to admit attempts to lose weight, even in an anonymous poll. The self-reported height of the average Israeli woman is 1.65 meters, while the average weight is 64 kilos. The average weight among those who said they were dieting is somewhat higher, at 71 kilos. The average body mass index (reported weight calculated against height) is 23.5, which is within the normal limits. Fully 58% of the women said their weight was within normal ranges (lower than BMI 25); 23% were overweight (BMI between 25 to 30); 5% were obese (BMI between 30-35); and 2% were morbidly obese (BMI over 35). 12% of the respondents refused to report their weight. Half of the women who were overweight or obese reported being on a diet. A fifth (18%) of the women who have normal BMI reported being on a diet as well. As women age, they usually gain weight, according to the poll. The average weight of women aged 18 to 29 women is 57 kilos, while those in their 30s and 40s gain another seven kilos. By age 50 and over, they weigh an average of 68 kilos. The poll's sample size was 250 women, and the margin of error was 4%. The NIHPR conference, about to convene for the seventh time and to be attended by leading decisionmakers in the health system from the Health Ministry, universities, hospitals and health funds, is to propose ways to promote public health and minimize smoking, overweight and lack of physical activity. Israeli teenagers are the 18th-most overweight in the world, according to studies to be presented at the conference, though Israelis are number one in the amount of time spent by adolescents sitting opposite a computer screen and in consuming soft drinks. There are to be three working groups at the conference, focused on the topics of: promoting public health through encouragement of healthful habits and discouragement of harmful ones; whether the health system is doing its job in prevention of disease and promotion of health; and how other sectors can contribute to these targets.