The magazine for alumni and friends of Massey University.
Issue 14, April 2002

Pyramid schemes: On why exercise should always be linked to good nutrition

In late 2002 a paper co-authored by Walter Willett, a researcher from the Harvard School of Public Health, gave rise to a flurry of headlines. The food pyramid with which Americans were all familiar had been overturned, ran the headlines. The received wisdom of the ages – or at least of a decade – was refuted.

The original pyramid, released by the US Department of Agriculture in 1992, had fats and oils among the foodstuffs at the apex; the new pyramid sits in a puddle of vegetable oil. The old pyramid advocated complex carbohydrates; the new pyramid does too, but they must be unrefined wholegrains.

Both pyramids advocate lots of fruit and vegetables.

But before you turn around the eating habits of a lifetime, drown your meals in olive oil, and tearfully consign all but wholegrain bread to the bin, you should realise that Willett’s conclusions are disputed. They largely derive from large-scale epidemiological studies, where people periodically have their health assessed and fill out questionnaires about their lifestyle. The trouble with such studies is the statistical difficulty of separating out the influence of particular factors. How do you compare a young sedentary drinker with a middle-aged exercising smoker who eats a fried breakfast every morning?

One aspect of the Willett wisdom that is not under dispute is placement of “daily exercise and weight control” at the base of the new pyramid.

No one disputes the nature of the most serious and intractable nutritional problem in the developed world: obesity. No statistician is going to quibble about the association between obesity and lifestyle diseases such as Type II diabetes, cardiovascular disease and some forms of cancer, or that being obese affects how people feel about themselves and interact with others.

A healthy weight is determined by a body mass index (BMI) score of between 20 and 25. BMI is a person’s weight in kilograms divided by height in metres squared (BMI = kg/m2). A value above 25 indicates that you may be overweight, and above 30 that you may be very overweight (obese). Fifty-two percent of New Zealanders are overweight or obese, and we are getting fatter. Between 1989 and 1997 adult obesity increased by 55 percent. In 2001 Ministry of Health was projecting that by 2011 it will have risen by a further 70 percent.

Why is this? Simply put, our calorific consumption has risen without our choosing to exercise any more than we did. The increase in calories is thought to be largely due to energy-dense snack foods, convenience or fast foods and sweetened drinks.

This is a global trend. Typically the Americans – whose leads we usually end up following – are consuming more and more calories, growing ever more obese and all while endlessly obsessing about finding just the right diet!

We are being endangered by our prosperity. By the cars, remotes, televisions – particularly televisions – and computers that encourage sedentary behaviour. By a social, economic and physical environment that promotes the consumption of energy-dense recreational foods. By new products, larger portions and the advertising to children.

How can you counter that? In the US the 2001 budget for the government’s ‘5 a day’ fruit and vegetable campaign was $1.1 million. McDonalds’ advertising spend that year was $1.1 billion. Would you like that supersized?

Efforts to address the obesity crisis need to focus on balancing our eating, physical activity and sedentary behaviours. The challenge is to gain a greater understanding of how these eating-related behaviours manifest. Fat intake, for example, is not a single behaviour but the product of a multitude of eating and other food-related behaviours. How do we change a lifetime of culturally shaped and socially defined habits?

In an attempt to curb the rising tide of obesity an initiative to integrate healthy eating and physical activity has been instigated by the Ministry of Health. In the 2002 discussion document Healthy Action –Healthy Eating the Ministry proposes a number of strategies for New Zealanders to achieve and maintain a healthy weight. There have, needless to say, been such exercises before.

The politics of obesity demand major changes in our thinking about food and physical activity. We need to truly believe that healthy eating and frolicking outdoors are more fun than gorging ourselves in front of the television.