"Psychotherapy is not a treatment for malnutrition." — Dr. Kim McCallum, founder of McCallum Place treatment centers for eating disorders
When it comes to ED treatment we have to prioritize treatment goals. The erratic eating patterns that those with ED's experience make them physically and mentally out of whack. The body and mind cannot function properly until stabilized with adequate nutrition.
Hence, food needs to come first in treatment. No amount of psychotherapy will work if the brain remains starved for nutrition. Think about it this way – the brain itself is made up of mostly fat and shrinks in size with starvation. The only fuel that the brain can use is glucose, a type of carbohydrate better known as "blood sugar." The brain alone burns 400-500 calories per day! And the chemicals in the brain that control mood are made up of proteins which are also influenced by food, carbohydrates in particular.
So, the brain doesn't work right if a person is in the throws of their ED. Even psychotropic medications (like antidepressants) may be less effective without proper nutrition.
Therefore, food must come first, a difficult reality for someone with an ED.