To me, body positivity is a reaction against the idea that fat people should hate ourselves, just for being fat - that the fatness is all that defines us. And being positive, loving your body, doesn't literally mean that you love being fat, but that you feel you are worth just as much as anyone else, fat or not. The hate towards being fat is so ingrained in you that it's really hard not to hate yourself, and to agree with the messages that society gives you that fat is one of the worst things anyone can be. The constant messages that you should have fat models showing how clothes look in case anyone is inspired to try to look like that (yeah right, it's so obvious hot much fat people are hated that it's not going to happen!), that clothes - especially nice ones - in larger sizes shouldn't be available in shops in case it makes being fat seem too normal (again, who is going to choose to be fat just because nice clothes were available?!), that if you're fat you shouldn't eat in public, especially treats, but also shouldn't exercise in public, etc. All of it just gives you the constant message that you aren't worth as much as a thin person. So body positivity and loving yourself -regardless of your body - is more what I think this movement was originally about; loving yourself despite(?) or perhaps including(?) being fat, as part of the whole package of 'you'.
And none of that is counter to losing weight. I have lost a fair bit of weight recently, not via jabs, but I probably would if I had had the opportunity. I probably would have been a good candidate in many ways - I am currently managing to control calories, but it's constant hunger and obsession about food and planning and what I am going to eat when, when will I fit in a long run to make up for it, how many hours of exercise etc - and realistically, I don't know if it's sustainable. It's miserable, that's for sure. I've done it before, and never managed to maintain, though with fewer hours of exercise before. It's a constant battle, it seems. And my blood work, other conditions etc isn't getting better anyway, which makes it even more of a struggle. I can't stop thinking about it for a day or I lose the will power and gain again. I don't think I have turned into someone with the mind of a slim person at all. Yet people will say that I've done it 'properly' because I haven't used the drugs, but honestly, I don't think it's different. People using the drugs are possibly happier while doing it, but they still have to cut the calories and treats almost completely, exercise for ages etc, if they actually want to lose the weight.
Do I feel more body positive now? Not really. I still know I've been fat for most of my life, have a likelihood that I will be again, and am very very aware of how I'm judged for it and treated when fat/slim, and I know what people think. They are more likely to make comments about fat people around me now that I'm less fat, and it's astonishing the depth of fat hatred that you can find in people you wouldn't have expected. The years living with the messages from society about how awful being fat is have had a long-term effect that is as hard to get rid of as the weight. I don't think people realise how much their judgements affect people - and not in a way that spurs them to lose weight, that's for sure.
And as for burgers and chips, yes maybe once a month or two I will eat out, and then I will have something that I've been craving for ages, what might seem like a full, unhealthy meal, but only because I've prepared and planned for it, possilbly run for ten miles earlier in the day, eaten extra mini portions for the week beforehand, etc. It might be the treat I've been looking forward to as motivation to keep on with the whole business. So don't judge your friends without knowing all the details of what they're doing. Treat them as if they're worth something regardless of size instead, and then maybe they will be able to make the healthy choices - it's much easier to treat yourself well and be healthy when you think you're worth it as a person.