Always more questions
In the average intake per person per day chart, there are two distinct and identicaly shaped dips for 2004-5 and 2008. I can't remember any national food shortages during those years or any national advertising campaign to eat less - so why the dips?
BMI: " ... there is no distinction between pure rippling muscle and unadulterated flab."
True, so BMI is not a good indicator of 'obesity' if you're a boxer, rugby player or a lumberjack, or very tall or very short. However, for the majority of the 'ordinary' population it is a reasonable and easy measure to take. So, unless the height or muscle development of the average population has changed much, it should be fine for long term use. If the average height does change then it should be easy enough to apply correction factors so as to make valid comparisons.
"Crucially, there is no measure there of waist circumference, which is what most of us use to make a judgement .."
What 'most of us' use to make a judgement is not medically uselful. From what I've read, the waist circumference in relation to chest and hip sizes can be a good indicator of future cardiac problems, so maybe these should be measured as part of the standard GP type of examination.
In the BMI category graph, there is a period of notable change between 1993 and 2001, then not much change after that to 2012. The BMI changes (for the worse) seem to coincide with the period of decreased calorie intake, though there are no figures for calorie intake after 2001. Does anyone know why this might be?
It all raises more questions than it answers, as do many of these types of studies.