Walter Kaye, MD, and colleagues performed a fascinating study applicable to this issue, revealing very useful data . They studied 17 patients suffering from Bulimia Nervosa. These women binged an average of 10 times per week and vomited 13 times per week. These women were brought into a laboratory, where they were offered food and asked to binge. They, in fact, did engage in the binge. The researchers were able to carefully monitor the food chosen and eaten by each woman and, therefore, were able to calculate the number of calories that were consumed during a binge. The mean caloric intake during a binge was 2,131 kilocalories (kCals). All of these women were of average weight. Dr. Kaye and colleagues then locked the bathrooms and brought out plastic buckets. Physicians, nurses, therapists and other health practitioners, who have worked with individuals who suffer from Eating Disorders recognize the intense drive to engage in purging behavior after a woman has binged. It is not uncommon after patients leave a hospital setting to find vomit hidden in corners of closets, in shoes, in drawers and in other locations where the patient attempted to hide it. Not surprisingly, the women in Dr. Kaye's study then engaged in purging behavior. The plastic buckets of vomit for each woman were then taken to a calorimeter and the number of calories determined. This allowed the researching team to identify the percentage of calories purged following a binge. Contrary to the usual expectation that at least 90% of calories consumed during a binge are purged, it was found that the mean caloric content of the vomit was only 979 kCals. In other words, less than 50% of the calories consumed during a binge were purged. This is a study that can be very important to patients who suffer from Bulimia. It helps to underscore the necessity to refrain from purging behavior and the futility involved in doing so. There are 3,500 calories in one pound, i.e., if you want to gain one pound in the next week, you must eat an average of 500 calories more a day than you currently are eating to maintain your weight. If you choose to lose one pound in the next week you must eat 500 calories less per day for the next week than you are currently consuming. The average number of calories consumed in the binge that were not then successfully purged would in and of themselves lead to a one pound weight gain every two days. Therefore, it is not surprising that patients who engage in binge and purge behavior, i.e., suffer from Bulimia Nervosa, tend to gain weight, unless they also engaged in severe restrictions during other times of the day.