Actually, I think part of the issue is the Government pushing exercise.
A lot of people are shit at sport and/or are still traumatised from their school days. But as the saying goes, 'you can't outrun your fork.' Exercise is good if you can do it, but the key to weight loss is actually nutrition. You exercise for health, you control your food for weight loss. They're not really interchangeable concepts.
You don't have to exercise to lose weight. People need to be made aware that they can regain control of their weight without having to wear lycra (which can feel like the worst thing ever if you're not happy with how you look).
People don't know how to cook and/or don't have time to cook. There needs to be more education around nutrition and how to cook reasonably healthily on a budget.
Education starts in schools, but for the adults who don't know how to feed themselves, we need fewer Masterchef programmes (where the nice food has loads of calories and is full of fat) and more programmes where healthy food is shown as within people's cooking abilities. Given the BBC is still funded by the taxpayer, that would be a good place to start.
Personally, I think WW is a load of overly complicated shit, but the Government could give away free subscriptions to weight loss programmes like that for anyone with a BMI of over, say, 28. So covering a bit overweight as well as obese. I think if you are very obese you can sometimes get access to these things through your GP, but they're not exactly easy to access.
More funding for tackling eating disorders would also be good. Part of our problem as a nation is a lack of nutrition knowledge, most of the rest of the problem is mental health related.
(There are some people who can't help putting on weight due to the medication they're on, but I'd suggest they are not the majority, and they have other health issues to focus on first.)