I'm a bit late to this discussion, but one thought that crosses my mind is about "free" gym memberships for the obese, courtesy of the NHS, and that 6tought is that, in my view, it simply won't work.
First, again in my view, most obesity problems (and I exclude genuine medical conditions which, though relatively rare, do exist) are far more about what you eat and how much of it you eat than they are about exercise. Yes, clearly exercise is critical to health and overall condition, but if you're cramming loads of crisps, cakes, chocolate etc down your throat, then virtually no practical mount of exercise is going to burn that off.
Secondly, gym usage is every bit as much about mental attitude as it is about cost. Quite a proportion of people that take out gym membership use it a handful of times, then it gets less and less, then they stop going, and that's when they have paid for it. The human condition is that generally, if it doesn't most you anything you don't value it, or at least, nowhere near as much.
In my view, the vast bulk (excuse the pun) of obesity problems are to do with what gets eaten, in what quantities. Someone I knew thought nothing of buying a 6-pack bag of crisps, and eating the lot in one sitting (usually in front of the TV). And that was NOT an isolated incident. Or of buying a multi-pack of biscuits and, again, munching though them until they've gone.
The result, a relatively small (as in short and light-framed) person ended up at, IIRC, 27 stone. And it caused huge problems. I won't go into them all, but essentially, this person, in their 30's, was told, in no uncertain terms, that they were causing huge system damage, damage to organs, and all sorts of complications that that they were, literally, not just wrecking their own quality of life but eating themselves into an early grave.
Harsh message, bluntly delivered, but true.
So, that person stopped eating crisps and biscuits. And I mean stopped cold. Portion sizes of meals when down, gradually but steadily, and the snacks between meals went from several bags of crisps to an apple or other fruit. They were still allowed chocolate, but as a weekend treat in the form of a small bar bought on a Friday, not as a 1kg slab, several times a week.
And what happened? Weight done from 27 stone to 16 stone, over the course of a few months.
And, as a direct consequence, some major breathing problems went away, they've gained in a sense of general well-being (i.e not feeling listless and knackered, 24/7) in a direct way to the weight coming off, they're more mobile, walk more easily, are having less joint problems and pain, so get out more and exercise more anyway, because even walking to the shops doesn't hurt as it used to.
With this person, that blunt message worked. It caused a change in what they wanted. And that's the critical bit. If you are obese, you have to really want to resolve that, because unless you do , nothing else is going to work. But if you do, it often is possible. Not easy, and it may well require help, encouragement and monitoring, and will will probably be damn hard over a period of time, but it can be done and it can be done with free gym membership.
To my mind, this issue with the cost of ambulances to cater for the obese is the tip of the iceberg. Yes, it's not cheap, but in terms of the costs of all the other medical implications of a national tendency to serious excess weight, it's a pimple on the backside of the problem.
The real problem is how you change the national mindset. How you get people to want to help themselves by watching what they eat, and especially, how you do it without seeming like a patronising nanny state. The state has to tread quite carefully in how it does this, or it could be counter-productive.
I also don't think taxing fatty foods is the answer. Not everyone that eats a fast-food burger or buys a packet of biscuits has a health problem, and for large numbers of people, you could quadruple the cost of burgers or biscuits and they'd have enough disposable income to carry on regardless. To really address the problem, you have to find a way to make people want to change how they feed themselves. You have to change mindsets, and attitudes, behaviours and habits. There's no guarantee the carrot will work (again, excuse pun) but the stick almost certainly won't.
It stands to reason, really. If this problem was easy to solve, it'd have been solved by now. There are no easy answers, and certainly, no easy top-down answers.