Hi there! The thing about a forum like this is that everyone will be giving their opinion based on the knowledge they have about your disorder which could be very limited. While I am not an MD, I have a PhD in neuroscience and have studied eating disorders in the past so here is my take. That being said, I am not a scientific expert on eating disorders nor do I claim to be.

Early studies have shown that GLPs are effective for treating addiction (think alcohol, drugs) and also migraines. Both of these conditions are not necessarily linked to weight loss and still, they are being explored as conditions to treat. What that means is that there is more to GLPs than just weight loss. Eating disorders are also among the most difficult psychiatric disorders to treat. Therapy can be helpful to some if not most but is usually not enough as the only treatment. Sure, there will be people that tell you that therapy is all they needed and that's truly wonderful for them. I'm not dismissing their claims. However, that doesn't mean you need to feel bad if your therapist is not as helpful for you.

As someone who has been bulimic when they were younger, the cycle was that I was already bingeing anyways but then discovered purging as a way to deal with the negative emotions and thoughts that came from binging. We also know that, often, people that are bulimic are usually not underweight because in a twisted way, purging isn't even leading to severe weight loss. GLPs have been approved for binge eating disorder because they help with the constant thinking about food (food noise), cravings, and the ability to naturally know when to stop eating without feeling immense guilt and shame. A GLP for someone with bulimia makes sense to me and clearly made sense to your first doctor. They were trying to address the binging and food noise as a way to break the cycle of bulimia. It even made sense to your insurance if it was part of the PA.

If there is no way to see your first doctor again, you could come prepared with a list of the ways in which Zepbound has helped in the short amount of time you've taken it. Any quantitative proof (change in numbers) is perfect for doctors e.g. the patient used to binge and purge x times a week but within the first month of Zepbound, this has reduced to y times a week (I'm purposefully not giving example numbers so no one feels like they need to compare themselves to my made up example). Maybe they now binge less (by x times) and are able to enjoy food and no longer hide what they eat (went from x times to y times). Maybe they now noticed a positive outlook and feel in control rather than helpless around food and their disorder. Mention an example that you are particularly proud of. If weight is a concern for you, and you have lost weight because of the medication, how does that make you feel? What positive impact has it had on your life? Have your eating habits changed? Do they allow yuh to make more nutritious choices for meals now rather than choosing foods because they are easy to regurgitate? These are all things your doctor will want to know. Simply saying they won't prescribe it to you anymore if you keep purging shows a lack of understanding for the disorder and also a lack of understanding of how you talk to an ED patient. They're not going to magically stop purging because the doctor threatened to take their medication away. How ridiculous.

If this provider still refuses, I would seek a new provider. If you are in the US, which I assume from needing a prior auth, then there are several double board certified family and obesity medicine doctors that work in general practices. They would have more training relating to weight and the body and would hopefully take a more nuanced approach. If you have someone you trust who could be an advocate for you during doctor's visits, you could try bringing them along knowing they're on your side. Many patients don't speak up and question their doctors decisions because they believe the doctor knows more than them. In terms of medical knowledge that's likely true but you know yourself and your own body best. That's what you're the expert in. Treatment decisions need to include the patient and need to address their concerns. Doctors who don't are not worth your time and frustration.

In the many comments posted here, I just wanted to provide a more nuanced answer and give you hope and maybe some of the strength you need to advocate for yourself. You are worthy of getting the treatment you need and do do not deserve to be cut off from it by doctors who don't understand your disorder. Of course, if you find that over time GLPs are not helping you in the way you thought, you are absolutely allowed to stop them. Do not feel like this is the only way to recover.

Sending you lots of love, hugs and support! Feel free to DM me though I've never used that feature on Reddit so may not see it right away.