Recently, I saw that a friend of mine had posted on her refrigerator a simplified list of food exchanges for diabetics. She does not have diabetes, so I asked her why she would need that list. She said that she wants to lose weight. I tried to explain that the exchange system is not a weight-loss plan. Its purpose is to help people with type 1 diabetes (insulin-dependent diabetes) figure out how much insulin to inject. And it does not do a particularly good job at that. She said that she was using the list to help her count calories.