You're wrong about a lot of points.
Treatment for anorexia nervosa is hard to come by. Mental health services are severely over stretched. The vast majority of people with an eating disorder are treated in the community, often just seeing their GP and very few see a specialist. Very few will get access to a dietitian, so will not be given a meal plan. Much like overweight people being told to "just eat less", people with AN are often just told to eat more. A lot of community dietetics services will not even see people with anorexia - there isn't the funding and instead they see people with diabetes, obesity etc because the Nhs is a business and obesity costs them a lot more each year than anorexia does so they don't see it as a priority.
Many people wait years for therapy, and in that interim period they either get steadily worse, die, or get better.
It is fairly rare for someone with anorexia nervosa to be sectioned and force fed against their will, despite what we may hear in the media. It's not that easy, and most patients are treated informally (not under a section). The emphasis in treatment centres is on normal eating, not tube feeding.
Obesity alone isn't a psychiatric illness, though as others have said binge eating disorder is. Everyone who is put forwards for bariatric surgery has to undergo a psychiatric assessment, and many do have BED/emotional over eating and will receive counselling for this.
You can't really compare the two in the way that you are. And actually a LOT more money each year is spent by and invested in the NHS in to obesity (and related illnesses) than eating disorders or mental health.
Posted from TSR Mobile