Given that ngata has me blocked and won't actually read this, I'd like to start by saying that Colin Kaepernick is braver than literally any US soldier other than Chelsea Manning.
Anywhom this is going to be a doozy that meanders a lot since I have lots of thoughts.
As someone who was obese, then dropped down to be fairly in shape, then has gone back to somewhat overweight, and is now working to drop back (250LBs to 150 to 200 and now in the low 190s): Food is fuel is the smart way to think about it, but it's not a truly realistic path to expect someone to follow. Food is a major part of every society on earth. Our brains are literally hard wired to prefer high caloric foods as a way to cope with the fact that back in the olden days your next meal was never guaranteed so you had to eat what you could while you had the chance.
But nowadays not only is food available, but it's abundant. And basically every social event is centered around food. You go to a party and there might be a veggie tray, but there will also be chips with dip, mozzarella sticks, and other unhealthy stuff. It's hard to stay around there for a long time and just avoid it because you know it tastes good. And you can trick yourself by saying "eating this shit won't really make a difference." Because that one time it doesn't. But you talk yourself into every single time just being an exception and before you know it you've gained 100 pounds. And that doesn't even get into drinking. You eat a great diet and have a few drinks a day and your diet is worthless.
Not to mention food is an incredibly easy pleasure to have in a life often devoid of it. So many people have to wake up early, go to work, work for 8 hours, go home, and get a little time before having to go to sleep and that's their day. So they're presented with the opportunity to either take the time to cook a nice chicken breast with a vegetable (a process that will take a half hour minimum) or they can grab a Big Mac with fries, something that we are biologically wired to enjoy more than the healthier meal, and it's just a 5 minute trip on the way home. And not even that much more expensive than making the chicken (and before you get back to steak, most people can't afford to have steak every night for dinner).
The other big issue with food to me vs other bad habits is that you can't just stop. A few years ago I had a bad breakup and i turned to eating and liquor for comfort (again, it's an easy pleasure). Basically every night I was eating a pizza or burgers or whatnot and getting drunk. Then one day I just woke up with an absurd hangover and it just snapped to me that I was going down a bad path. So I stopped drinking for awhile. I knew that I had to so I stopped buying alcohol, so there was no alcohol around me, so I didn't get drunk. Food is tougher because you can't just stop eating. This could just be me, but moderation is harder than completely abstaining.
And I haven't mentioned exercise in this because in my experience exercise is pretty much worthless when it comes to maintaining weight. When I really decided to start losing weight I started going to the gym a lot. Even as I gained a lot of it back, I still was going to the gym. The gym is good as a mental habit to keep at it (plus the other benefits exercise provides) but one slice of pizza undoes an entire workout from a caloric perspective.
As far as body positivity goes, I do think it is good to an extent. Fat people are treated like shit by society in a way that isn't ok. All the research indicates that being shitty to fat people doesn't help them lose weight. In fact, it often drives them to eat more since they feel shitty about being called fat, and like I've said, food is a quick, easy pleasure. People shouldn't feel subhuman because of their weight, and if they really decide the enjoyment they get out of food outweighs the negative side effects from their weight, that's their choice. People who tell themselves that they're dicks to fat people for their sake are just looking for an excuse to bully people they deem inferior to themselves.
Where I do have problems with the body positivity movement is that my guess is that it's something of a lie people tell themselves. With probably a few rare exceptions, I would bet most body positive people would rather be thin if it was possible without having to change their lifestyle. The people who spread misinformation about dieting piss me off. There's that famous study that showed 98% of diets fail, and while thats true, it's because people don't stick to them. People like to use that to say that some are naturally fat or thin, but that's just untrue. If you diet and don't let yourself fall back into bad habits, you'll never gain weight. People are also horrible about estimating the calories they consume, which is why they think they can't lose weight (which feeds the mindset of "I'll never be thin so might as well eat more).
Now with that all being written, if someone truly has an eating disorder, they probably aren't going to get through that without actual psychological help. Ngata's cousin needs to see a real therapist to help him get to the bottom of his disorder. Binge eating disorder is hard to diagnose since it's so similar to the typical western lifestyle, but it is different. But even if he gets past the disorder, it's still a massive difficulty to lose the weight and keep it off.