for a few years now i've taken a casual interest in obesity. Not actual obesity but the facts around what seemed to me to be at least somewhat a scare. Every February the NHS publishes a report. It is here:https://catalogue.ic.nhs.uk/publications/public-health/obesity/obes-phys-acti-diet-eng-2013/obes-phys-acti-diet-eng-2013-rep.pdf and past years may be found by googling. There's a lot of data, some dodgy stats and a trend far smaller than what you might have come to believe. But what I wanted to show you is the fine example of model predictions below. Because it has parallels in climate and elsewhere What follows is all quoted from the text:

There are various research reports and journal articles available that use HSE data to predict future obesity trends in adults. The report by Foresight at The Government Office for Science produced the Tackling Obesities: Future Choices report14 which provides a long-term vision of how we can deliver a sustainable response to obesity in the UK over the next 40 years. HSE data from 1994 to 2004 were used as a basis of modelling obesity prevalence up to 2050.

By 2015, the Foresight report estimates that 36% of males and 28% of females (aged between 21 and 60) will be obese. By 2025 it is estimated that 47% of men and 36% of women will be obese. In a few years we will be able to compare against these modelled estimates. At the moment, the HSE 2011 data shows that the current rate for obesity is 24% for men and 26% for women.

Another research report published in 2008 by the British Medical Journal Group, Trends in obesity among adults in England from 1993 to 2004 by age and social class and projections of prevalence to 201215 predicted that the prevalence of obesity will increase to 32.1% in men and 31.0% in women by 2012 based on 1993-2004 obesity prevalence trend data.
The predicted 2012 obesity prevalence for adults in manual social classes is higher (34%) than adults in non-manual social classes (29%). The report also concluded that if recent trends in adult obesity continue, about a third of all adults in England (almost 13 million adults) would be obese by 2012, of which around 34% will be from the manual social class. HSE 2012 is expected to be published in December 2013. Comparisons against these modelled estimates will then be possible. The definitions of obesity used are contained within the publication. These do differ, which will need to be taken into consideration when attempting any comparisons.

TBYJ, I have a memory of a rtime when the BBC was not so monolithic in approach. I remember heaing on Radio 4 a documentary suggesting that all the fuss about obesity was msplaced. Probably a File on Four programme (No, an 'Investigation'). The presenter took some obesity nazi NHS spokeswoman into a school playground and asked her to point out the obese kids. Should be easy if it's 20% (or whatever they claimed). She could not do it and was obliged to fall back on bluster that you can't tell the BMI by looking. I mentioned the show on some blog or other at the time and got an email back from the producer, one Richard Vadon.

And I found a link to this or a similar show http://news.bbc.co.uk/1/hi/magazine/7105630.stm

So the BBC at least has toyed with a sceptical approach.