It's easy to be judgy about other people whose experience you don't share, and Mumsnet is a minefield of it.
Lots of self righteous "I have done this so I don't understand why everyone can't"
I guess a great analogy for me would be - some people do brilliantly well at school, some don't.
Of those that do, there are a fair number that seemed to be naturally gifted and excelled without really putting a finger. There are others who grafted really hard to get their results, and made sacrifices.
Equally of those who did badly, some were likely naturally hampered by learning difficulties, which were no fault of their own. Some of those tried really hard and achieved what they could, and maybe we're really happy with that, knowing they had overachieved their expected level.
Others were completely uninterested in learning or had behavioural difficulties that meant they found it difficult to concentrate.
So e of that may be due to environment, parents, some not.
The analogy is that weight loss and gain are similar.
There are some thin people, like dh, who have a naturally low appetite. If you look at the family you will see that there is a "thin gene" of low appetite. My daughter is the same.
Equally there are people who make thin-ness a big part of their life goals. They work out, they eat healthily. Maybe they have some genetic help or maybe they don't.
On the other side, there are people who struggle with weight from childhood onwards. Whole families of obese people. There are also people who could genetically be thin, with a manageable appetite, but are struggling with bad habits, in an obese environment full of hyper-palatable food, or who don't care that much about weight.
And there are other people whose weight is the least of their problems. Their only pleasure in their hard life is food. Or those whose mental health issues have led them down a path to food addiction.
None of these groups are comparable. A naturally thin person can never identify with someone who is addicted to food. They can't grasp what on earth it feels like to be that person, and vice versa.
Personally, substance abuse is in my past, and at some point in my recovery I seem to have switched to food. I didn't notice it happening until I realised I was on a yo-yo of dieting then "eating as an Olympic sport".
I think the government is right to encourage people to lose weight. But it's not helpful if all that does is give smug thin people the justification for feeling superior. Which many of them already do, because I know them. They actively look down on the obese as lesser forms of life. Along with smokers, alcoholics etc.
But we all have a different starting point and a different journey.