Thursday, March 11, 2010

Growing up in Ireland: obesity amongst 9 year olds

I have been looking at the Key Findings for the Growing up in Ireland data (9 year olds). There is lots of interesting information there. One thing that caught my eye was the extent of obesity:
Apparently 26% are overweight or obese. The figure for girls is 30%. This is much higher than I would have expected (never having studied the topic) & seems pretty alarming. Does anyone know how this compares internationally?
The incidence is also much higher amongst lower SES groups.


Colm Harmon said...

Yes Kevin - the rate of change in obesity in Irish kids is the fastest in the western world

Alan Fernihough said...

Obesity and overweight are not the same things at all. The actual obesity figure is 7%.

I am known skeptic of BMI. This measure has a lot of issues, which I've raised before on this blog. So if some kids are just going over the threshold from 'normal' to 'overweight' I wouldn't be too worried. In fact, I'd almost see it as a good sign of increasing bone density and muscle mass which ultimately leads to healthier much more productive adults.

Don't get me wrong, I wouldn't deny that child obesity has risen and it's a bad thing. However, the way which these often ad-hoc statistics are thrown around does very little to inform the debate IMO.

Kevin Denny said...

Alan: my post was careful to distinguish between being overweight and being obese. The limitations of a simple index such as BMI are well known. But I'm curious to know the basis for your suggestion that high values of BMI - in these ranges- are more likely to be a good than a bad thing. That seems pretty ad hoc to me.

Peter Carney said...

Our in-house child-BMI specialist, Ms. E. Hudson, tells me that kids don't have significant muscle mass, owing to their lower levels of testosterone.

Can we agree that the WHO has put some thought into these guidelines and that they are useful for monitoring population trends?

Peter Carney said...

Our old gender equality concerns might be abated by the fact that only 53% of children had a male principal.

But its also interesting to note that 86% of 9-year-olds are taught by women.

Kevin Denny said...

On the BMI data, I think thats the safest conclusion. I wonder is there a sex difference: i.e. is the lack of muscle-mass more of an issue for girls, for example?
On teachers: I think its well known that it is dominated by women except at the top. There is a certain kudos to having a male principal. However I think there has been an increase recently in males doing teacher training although I doubt that this will reverse the long term trend.

Eibhlin said...

The WHO/UK90 cut-offs for children are calculated separetly for girls and boys. I'm assuming Kevin is using those rather than the cut-offs for adults. These are based on the LMS method (developed by Tim Cole) which try to account for different stages of puberty, etc, in particular adiposity rebound. To my knowledge, muscle should not really be a problem until the teenage years-It is very difficult for a 9 year old boy or girl to develop muscle. In Ireland I would guess that bone density levels have been stable for some time. I would imagine this is more of an issue with developing countries who are teasing out obesity/health problems with their children. I think for Irish children the BMI cut-offs (based on z-scores) are more reasonably reliable indicator.

Peter Carney said...


A few things here:

Women naturally have more body fat and men have more muscle mass. For BMI the basic metric uses body weight and body height; with no distinction of fat or muscle.

Alan's concern, in general, applies mostly to adult males that have built extra muscle mass. Their BMI will have them classified as overweight (muscle weighs heavier than fat) even though they are not carrying extra body fat (which is generally the unhealthy bit). So, yes, BMI is an inaccurate measure of being "over-weight" for body-builders, strength athletes, and people tending in that direction. The criticism is fair up to a point and that point is 30 - Obesity.

Women and prepubescent children are likely to have more body fat, pound for pound, than adult men who are more likely to have more muscle mass. Considering such ratio would suggest that for a level of excessive BMI over 25 and up to 30: see to the women and children first.

For the children, I don't see any reason to distinguishing clinical concern between boys and girls in childhood obesity. But perhaps there is reason to think girls will find it harder to 'grow-out-of' than boys who will have the assistance of muscle mass development in adolescence. In this sense, obesity could be more of an issue for girls than boys.

Kevin Denny said...

Thanks, very informative!

Kevin Denny said...

Eibhlin, I was just quoting what was said in the study's Key Findings which didn't specify which particular values of BMI they used but my guess is that they were up-to-speed on this.

Alan Fernihough said...


This is the sentence in your original post:

'One thing that caught my eye was the extent of obesity:Apparently 26% are overweight or obese. The figure for girls is 30%'

The extent of obesity is 7%, or two children in class of thirty. IMO your post was misleading. You say the extent of obesity caught your eye, yet you quote the figures for something else.

Peter, Eibhlin:

You are missing my point. I am not saying that there are a bunch of 'overweight' bodybuilder kids or whatever skewing the data. What I am saying is that BMI IMO is a bogus measure of 'health'/whatever, because it was developed in the early 1800s. I guess you either believe the musculoskeletal mean in the western world has remained constant since the early 1800s or you don't.

I am not saying that obesity in children should be ignored. However, I remain skeptical that the overweight category is really any concern.

Kevin Denny said...

Alan: now you are being silly

Liam Delaney said...

Moderator Time:

Alan, it is clear that Kevin did not mislead in the post. He said "overweight or obese". This is not as informative as putting in both figures so you are correct to clarify this. End of that discussion in my view. Kevin, "silly" is an inflammatory word that might disturb the tranquil vibe of our longstanding forum.

At some stage Alan, post up a few papers that clarify your point about BMI being a relatively poor marker compared to other measures that take into account muscle and so on.