Lot of excellent insight in this thread so far. Perhaps Mumsnet should use this to make a submission to the department of health, since they can't work it out themselves.
Something that has not been mentioned so far is malnutrition. This is entirely preventable (with the exception of very advanced chronic disease), and contributes significantly to poorer health outcomes in the elderly.
For example, a malnourished individual is far more likely to experience sarcopenia (Muscle loss) which leads to frailty, falls, hospitalisation, and death.
Malnourishment costs the NHS a lot of money every year, easily comparable to obesity, and just as preventable. More education directed at people in their late 50s onwards on best practice health management as they age, on how to prevent/delay ending up in a care home would be very useful, as a way to save money.
And oral nutritional supplements (ONS) such as Fortisips or Ensures, should NEVER be prescribed outside an acute setting without full assessment and recommendation by a dietitian. Then ongoing re-assessment until patient can be weaned off ONS. They should never be used as a food replacement, should not be prescribed simply because patient or family ask for them, and they will not bring a dying person back to life.
To put the cost of ONS into perspective, one serving per day costs upwards of £400 per year. There are far too many patients in the community, who are on 4-5 servings per day, and have been for years.
it all comes back again to individuals taking more responsibility for maintaining their own health as far as reasonable. instead of relying on the NHS to fix something that they broke.