At first, the background for eating disorder treatments was, "a calorie is a calorie". At that time, people involved in the eating disorder industry didn't know that metabolic waste - faeces, urine, sweat, exhaled breath, etc. have calories.
Like the academics in the weight loss industry, people in the eating disorder industry believe that every single calorie in food uptake, if not spent on basal metabolism or burned through physical activity, will be converted to fat mass. They didn't question any model of obesity, like "a Calorie is a calorie" or Calories In Calories Out - Energy Balance Model (EBM)", the Carbohydrates Insulin Model of Obesity (CIM), etc. Note: When the weight-loss professionals, obesity researchers, and academics involved in obesity research realised that metabolic waste (faeces, urine, sweat, breath, etc., contains calories), they abandoned the model "A calorie is a calorie" and replaced it with the new model called the Energy Balance Model of obesity (EBM). The Energy Balance Model of Obesity (EBM) is widely known as "Calories In, Calories Out". At the same time, the Carbohydrates Insulin Model of Obesity (CIM) is introduced, a kind of supplement to the Energy Balance Model of Obesity (EBM) - Calories In, Calories Out.
The NHS website's answer to the question "what causes eating disorders" is "we don't know what causes eating disorders." ... "Eating disorders are attributed to factors like body image distortion (BID), biological factors, a desire for perfection, rarely being satisfied with what you've done, being very critical of yourself, being overly competitive about things, etc.."
The official view about the cause of eating disorders is wrong and is born out of eating disorders specialists thrust on theories like, "A calorie is a calorie", Calories In - Calories Out (Energy Balance Model), Carbohydrates Insulin Model of Obesity (CIM), etc.
Eating disorders professionals are reluctant to face the fact that eating disorders were almost nonexistent before pseudoscience of weight gain/weight loss took the foothold.
Academics researching and treating eating disorders (anorexia and bulimia) are reluctant to admit that fear of gaining unwanted body weight and the pseudoscience of weight gain/weight loss is causing eating disorders.
Guided by pseudosciences like "Calorie is a calorie" and "Calories In - Calories Out, " also known as Energy Balance, every underweight person is diagnosed/labelled as anorexic or bulimic, and everyone who is overweight or obese is diagnosed/labelled with a binge eating disorder. Thus, every underweight person is labelled as (undereater) and at the same time as mentally ill/diagnosed. And every overweight and/or obese person is as (overeater) sick mentally labelled/diagnosed.
Every underweight person is diagnosed/labelled as anorexic or bulimic, and everyone who is overweight or obese is diagnosed/labelled with a binge eating disorder. If someone is of average weight, overweight or obese, he can't be diagnosed with anorexia. They can only be diagnosed with atypical anorexia because it is the eating disorder professionals believe obese people purge after overeating.
Apart from rare examples of anorexia (medieval saints), anorexia was unheard of before pseudoscience of weight gain/weight loss took the foothold.
An even more straightforward example is diabulimia. Diabetes type 1 with disordered eating (T1DE) or diabulimia is an eating disorder that only affects people with type 1 diabetes. It's when someone reduces or stops taking their insulin to lose weight.