FreightTrain:
Support them and appreciate them no matter their weight. If they want to lose weight so be it. If they aren't really into it but aren't doing anything to lose weight appreciate what you have now, not as a focus but just in general. With love and support they may eventually find comfort in their own body but that's something they need to find for themselves.
Hela:
I love him so much and his weight does not matter and I know that he likes this lifestyle and that is the problem. I know that when he loses weight, he gains it again, because naturally he eats a lot and loves high-calorie dishes. Sometimes he have large complexes because him old clothes doesn't fit
That's great, It sounds like you're doing your best and I'm sure they appreciate it. As for their weight fluctuation it's kinda on them at this point. I suppose you could ask them if they want you to intervene in anyway and support their diet at all or just kinda continue on as normal.
Ultimately it's something they kinda need to figure out for themselves. The best way to go about it is to continue giving them support and hope that maybe the fact that they have someone who loves and supports them unconditionally aids them in finding comfort in their own skin.