So what is wrong with the 'exchange system'?
Unless you have an eating disorder.
I don't know the history of the 'exchange system', which is often used in the field of nutrition. I don't doubt that it's been useful for many people who may need some structure for eating, due to any number of medical illnesses.
What I DO know is that it's likely the worst possible approach to meal planning for someone who is in treatment for an eating disorder.
If you are reading this, you likely know that the mindset of someone suffering with an eating disorder is not usually rational. This in itself is due to malnutrition and [likely] being in a state of starvation. Even people who struggle with bingeing and purging are starving. Their bodies are being deprived of consistent, adequate nutrition.
The eating disordered mind thinks in terms of 'less' and 'smaller' and often classifies foods as good or bad.
With the exchange system of tracking food intake, you have four or five major food categories which make up your recommended daily intake. Within these categories you may have numerous choices, which are supposedly interchangeable. The truth is, when you compare nutritional value (calories), these choices could vary up to 50-75 calories among items in a certain category. What do you think the person with the eating disordered mindset is going to choose? Naturally, they will always pick the lower calorie item. Don't doubt for one minute that they don't know which item that is.
For example, apples can vary greatly in size, and up to 50 calories based on their size. The same goes for a slice of bread. Different types of bread can also vary at least this much.
If you consider a person's intake for an entire day, and they have made these choices with an eating disordered mindset, they could end up eating several hundred calories less than if they had made different choices within those food categories.
If you don't have an eating disorder, and never have, I can't begin to explain or help you comprehend the power of that eating disordered mindset. The person cannot help but choose according to their eating disordered beliefs.
Precise calories is the only sure and safe way to develop a recovery meal plan. Unless you know the precise and exact calories that you are eating, there is no way to know how your body will react to food and calories. This is also the only way to challenge the fears that a person with an eating disorder has about food. There is a science behind this, in terms of using this concept in treatment. I am not a scientist, nor do I claim to be. But I do know, without a doubt, that this works. Otherwise, I would not be alive tonight to write this.
Counting calories can be a healthy thing when used for recovery, and it's a way of maintaining control, while learning how to let go of unnecessary control of other areas of your life.
Meal planning and counting calories is necessary for effective treatment, but it doesn't have to last forever.
Believe me, it's much better than living [or dying] with an eating disorder.