New report rewrites the obesity trends - or does it?

Obesity trends in children are levelling off, says the National Heart Forum in a new report. Hooray, we’re not going to be quite as fat in 2020 as we thought we were.

But nothing has actually changed, except the projections made from data that are inadequate to support the conclusions drawn. The new report says more about how poor the ability to project these trends is than it does about obesity now, or in the future.
On the face of it, the new figures are wonderful news. For example, instead of 19 per cent of teenage boys being obese in 2020, as the Foresight report predicted in 2007, the new estimate is that just 6 per cent of them will be. Among girls in the same age group, the proportion falls from 30 per cent to 9 per cent.
How has this miracle been achieved? Merely by adding three years of additional data from the Health Survey for England, which were not available in 2007 when the Foresight team published its report, Tackling Obesities.
The same team, led by Professor Klim McPherson, is responsible for both reports – so it cannot even be argued that different methodologies have led to different results.
If three years of data can make such a huge difference to the projections, either something dramatic has happened or the projections are wrong. The latter is a far more likely explanation, because nothing dramatic has happened. The national strategy to tackle obesity, launched by the Government in October 2007 in response to Tackling Obesities has not had time to have any effect yet.
Figure 3 from the Heart Forum’s summary report (below) compares the Foresight projections for teenage boys up to 2020 with the new projections. The three categories are shown in green (normal weight) blue (overweight) and red (obese). In contrast to the sweeping curves of the Foresight report, and its wide confidence intervals, the new report shows almost flat trend-lines for all three categories.
The original Foresight projections were strongly criticised in a report for the Department of Children, Schools and Families by a committee under the chairmanship of Professor David Buckingham. These criticisms were published by Straight Statistics – and so far by nobody else, since DCSF has not yet seen fit to publish the full report.
The last time I asked, I was told it would be published in the autumn of this year. We’re now past that, and still no sign.
The Buckingham report, when it finally does appear, should contain a technical appendix casting doubt on the Foresight projections. This says, inter alia, that over time and without Government intervention, a significant number of people will modify their diet and lifestyle, making the projections meaningless.
Alternatively, it says, “it might be better simply to acknowledge that we currently have no scientific basis for making such long-term projections.”
The new report, by the same team that made the earlier one, rather confirms this conclusion. By adding three more years of data, it transforms the projections for 2020.
The results were welcomed by the Minister for Public Health, Gillian Merron, who said: "The encouraging news that child obesity may be levelling off is thanks to the hard work of families, schools and the NHS across England, supported by Government initiatives such as 5 A Day and Healthy Schools  which have overseen improvements to school food and school sport.”
That’s wishful thinking. The data used to make these projections only goes up to 2007, before the big government push against obesity even began. The Government didn't even have any worthwhile data from the Child Measurement Programme. What we have here is not a real change, but an artefact produced by the projection methods.
I didn’t believe the Foresight claims, and I don’t believe these. If they are right it will be more by luck than judgement.