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Last Updated: Thursday, 22 November 2007, 09:20 GMT
Cost of obesity 'over-estimated'
By Richard Vadon
Radio 4's The Investigation

Obese family
Obesity is a major public health problem
A major government study has over-estimated the future cost of obesity to the UK by at least 10bn, according to a BBC investigation.

The Foresight report put the cost to the UK by 2050 at over 45bn a year, almost half the NHS budget.

But Radio 4's The Investigation found the estimate was based on a misreading of figures from a parliamentary report.

The report's author admitted to the programme that he had made an error but claimed that it made little difference.

The calculations were based on a Commons Health Select Committee Report which estimated that in 2001, obese people cost the NHS 1bn a year.

But the calculations for the Foresight report failed to notice that figure doubled to 2bn when allowing for the costs of both obese and overweight people.

COSTS OF OBESITY/OVERWEIGHT
Parliamentary report: estimates for 2001:
Cost to NHS: 2bn
Cost to UK economy: 7bn (3.5 times greater)

Foresight report: estimates for 2050:

Cost to NHS: 6.5bn
Cost to UK economy: 45bn (7 times greater)

The parliamentary report also said that the overall cost to the UK economy allowing for time off work and early deaths was 7bn or 3.5 times the 2bn cost to the NHS.

Foresight looked ahead to 2050 and estimated the NHS costs would have risen to 6.5bn.

Scaling that up to find the overall cost for the UK economy they should have used a ratio of 3.5 to give an overall cost of 22.5bn. Instead they multiplied by 7 to obtain a figure of 45bn.

Revised estimate

The man who led the team responsible for the Foresight figures was Professor Klim McPherson, an epidemiologist from Oxford University.

It shows how important it is to scrutinise any report that comes out about health issues especially making long term projections
Professor David Speigelhalter

After being challenged over the figures, he gave a revised estimate where total costs in 2050 had shot up to 57bn.

Several days later he changed this figure, this time down to 49.9bn.

The programme sent the Foresight figures to several respected statisticians. One called them "fatuous".

Another said: "The general sloppiness of this section is evidence to me of poor quality work."

Professor David Speigelhalter, a statistician from Cambridge University, looked at the figures too.

He said the Foresight team had made "a basic logical error in their calculations".

Asked if it was embarrassing for them, he replied: "You could say that".

Speculative

Using the same figures as the Foresight team, Professor Speigelhalter produced his own estimate for future costs of obesity and overweight - 34bn, over 10bn less than the original Foresight estimate.

Professor McPherson stands by his figures: "You can contest any of these multiplication factors, they are all a bit speculative but in my judgement the safest assumption was to take the most reliable costs and that is where you get the factor of seven."

His response to critics of the quality of his report was that they were wrong.

"This has been through the Department of Health, Economics Department, and has been read by experts from various of fields. Nobody has said such a thing."

Does it matter when both figures are so big?

Professor Speigelhalter says it is vital we get them right: "It shows how important it is to scrutinise any report that comes out about health issues especially making long term projections."

The Investigation - The Truth About Obesity:
Radio 4, 2000GMT, Thu 22 November.
Online from Radio 4's
Listen again page.
Podcast from the
File on 4 website.



SEE ALSO
The truth about obesity
22 Nov 07 |  Magazine
Not that naughty but still nice
16 Oct 07 |  Health

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