Robert Scragg: Battle begins over health effects of takeaway food

COMMENT


An article by Jeremy Irwin, of the Association of New Zealand Advertisers, on whether takeaway foods are contributing to the obesity epidemic contained a number of misleading interpretations of the Ministry of Health's national children's nutrition survey.

As a contributing author to that report, "NZ Food/NZ Children", I have a number of concerns.

Mr Irwin has a limited understanding of body mass index. For example, he describes BMI as the ratio of height to weight, when, in fact, it is the ratio of weight to the square of height (using metric units).

Far from being a crude measure of obesity and used as a screening device only, it is the main measure used internationally to monitor obesity levels.

Mr Irwin implies that the increasing prevalence of obesity in New Zealand and other countries is due mainly to a change in definition. This is not true.

Dr Noela Wilson, of the University of Otago, presented data at the recent Nutrition Society annual conference that showed the weight of New Zealand children had increased greatly since the mid-1980s.

Comparing 14-year-olds in a 1985 national survey with those in the 2002 national survey, the mean weight for girls increased from 54.9kg to 60.7kg, and for boys from 57.1kg to 64.4kg, with little or no change in height between the two surveys. These are substantial changes, roughly equivalent to an average weight increase of a stone (in Imperial units), and are of great concern for the long-term health of our children.

Mr Irwin has misinterpreted the data on burgers collected in the national survey. He implies that this food item exclusively represents takeaway foods, when, in fact, other food items, such as chicken, which was consumed weekly by 83 per cent of New Zealand children, and fish, which was consumed weekly by 37 per cent, would also have been bought from takeaway outlets.

He is correct in saying that burgers represent only a portion of total food intake and cannot by themselves be solely responsible for children being overweight. But the national survey found a strong association between the proportion of obese children and the proportion eating burgers weekly, when comparing socio-economic sub-groups.

The likely explanation for the association between eating burgers and obesity is that burgers are a marker for the intake of other foods causing obesity, and that children who eat burgers weekly are more likely than other children to regularly eat other fatty foods, such as chicken, which in combination with burgers contribute to obesity.

He implies that intake of fatty foods is determined more by individual choice - which neatly turns the spotlight away from advertising - than our environment.

But most public health professionals would give greater importance to the latter. During the 1990s they gradually realised that weight-loss strategies based on trying to change the behaviour of individuals had limited short-term effects because people coming off weight-loss programmes usually put their weight back on within a few months.

This is because those who are prone to putting on weight find it very difficult to overcome the many drivers for obesity operating in our environment. These include a plentiful supply of fatty foods, advertising to encourage the eating of these foods, limited money to buy healthy (more expensive) foods, prolonged watching of TV, and limited facilities for exercise.

The term "obesogenic environment" has been coined to describe these structural factors causing obesity. Any balanced discussion about the causes of obesity should include both individual and environmental factors, not just the former.

Mr Irwin says that advertising has only a limited influence on food choices. This is on old argument used by the advertising industry. Yet while it claims that its trade has a limited effect, millions of dollars are spent annually to get us to buy its clients' products.

The advertising industry takes the position that if a product can be sold legally, it should be legal to advertise it. For unhealthy products, such as cigarettes or fatty foods, this is a morally indefensible argument - and ultimately irrelevant because, as we have seen with cigarettes, public and political opinion will eventually turn against the advertising of unhealthy products.

The Association of NZ Advertisers is clearly concerned about possible changes in public attitudes to the acceptance of advertising unhealthy foods, particularly during children's TV programmes.

Its potential revenue sources have been damaged by laws restricting tobacco and alcohol advertising; it fears a similar outcome for the advertising of unhealthy foods if the rising tide of obesity in children and adults is not stemmed.

We are witnessing the start of a long-term war for public opinion over strategies to deal with the rising obesity epidemic between the advertising industry, in league with some sections of the media and food industry, and public health professionals.

If the earlier war over cigarette advertising, between the tobacco and advertising industries and the health sector, is any guide, the battle will be a drawn-out affair. But the viewpoint of health professionals will, again, prevail because the public will eventually perceive that health professionals are acting in their interest on this issue.

* Robert Scragg is an associate professor in epidemiology at Auckland University. He is responding to the view of Jeremy Irwin, of the Association of NZ Advertisers, that takeaway food is overemphasised as a factor in obesity.