Tuesday, February 07, 2006

Getting fat in Australia

I talked to researcher Samantha Farmakis this afternoon about her work on obesity and, yes, some interesting things already seem to pop out. As measured by trends in BMI since 1990 Australians are getting fatter -- no ambiguity about that (there is elsewhere in the literature!) except for some bizarre trends at older ages. There are questions about the appropriateness of BMI calibrations of obesity that we need to note and it would be nicer to have a longer time series. New data is arriving soon this year.

One point was that exercise levels have not fallen so this does not seem to be the rationale for us getting fatter. It might be that overall activity levels have fallen even if exercise levels have not so we need to sort out this data. Indirect data suggests people drive further to work so perhaps they walk less. We need to be careful about the definition of 'exercise'.

Food prices do seem to have fallen though not, on inspection in areas where we might expect weight problems to arise -- sweets, confectionary and fast food prices seem to have galloped away.

Data on smoking and alcohol consumption exists. Both have fallen off a bit recently.

Income levels have risen but as food is a normal necessity this seems an implausible explanation of sharply rising obesity.

Data on female work force participation would seem to be useful though dominated by trends that have declined.

Anything else? I am a bit of a fatty myself so I want to know.

Update: An interesting review by Andrew Leigh is here.

5 comments:

Anonymous said...

One question that comes to mind is that are these trends for averages, or has there been a shift of the entire distribution of BMIs. This question arises because of (1) Publicity about anorexia (2) Publicity about personal trainers/exercise fads etc (e.g. there was a story in The Age recently about this). Was the distribution Normal and then shifted up - or have the tails become fatter (no pun intended) or the distribution more skewed?

Anonymous said...

My favourite paper on this is Cutler, Glaeser & Shapiro in the JEP last year (blaming technology, not exercise). They have a nice discussion of why Posner's changing jobs theory doesn't help explain the post-1970 rise in obesity.

I wrote the CGS paper up for an SMH oped in 2003 or 2004 (see www.andrewleigh.com if you're interested).

Like the site, BTW. But the black background is almost illegible on my laptop.

Anonymous said...

My hobby is collecting popularist books on sleep medicine. The latest one I bought is called the Doona Diet which has references to papers about insufficient sleep leading to weight gain.

The theory is that artificial lighting makes your body think the days are longer and gets the impression you are perpetually in summer. This causes your body to store away food in fat deposits for a winter which never comes.

Vicki said...

Ummm it's a lovely navy blue background for me. :-)

Now (disclaimer!) I'm not an economist, but this article shows that in many instances food prices have risen a lot.

I don't know the validity of the research (which deals mainly with primary produce) but maybe someone can correlate that with prices of junk food...

Another point of interest may be how much alcohol Australians are consuming. I always get a wry chuckle when overweight people say "I don't know why I am overweight because I really don't eat much!" as they tuck into their first glass of whatever for the day - at midday. :-)

hc said...

Getting back to the comment by anonymous. We tested your hypothesis about distributions and you do get interesting effects. The distribution is getting more positively skewed. The thin are getting thinner and the fat are getting fatter. This is particularly noticeable among old people 75+. Also lots of old people are heavy dispelling the widespread presumption that having a bit of weight is bad for your health. Quite a few heavier people survive.

Now testing for differences by gender and will report back.

A useful comment that helped us so thanks!