OPINION: The ups and downs of the Australian cricket team have certainly provided gripping drama this summer. Far less edifying has been watching on TV time and time again as cricket greats both past and present team up with the fast food industry.

Excess weight is a national emergency. Obesity has now overtaken smoking as the leading cause of premature death and illness in Australia. Fifty-five per cent of us are either overweight or obese; healthy weight is now a minority position. Yet the most alarming story is what is happening to our children.

One in four Australian schoolchildren is either overweight or obese, a figure that has more than doubled in the past 25 years.

Disturbingly, if an adolescent is obese, the chances of staying obese during adulthood are high. Some of the medical consequences are well known - increased risk of heart attack, diabetes, cancer and premature death. Indeed, best projections suggest that the current generation of school children may be the first since Federation to experience a shorter lifespan than their parents.

The quality of this contracted lifespan may also be diminished, for less well known are links between obesity and mental health issues such as depression and, of course, the burden of excess weight on the self esteem of young minds.

Fast-food advertising during prime time and children's TV is contributing to this state of affairs. Certainly, there are several factors weighing on this complex issue, but the bottom line is energy imbalance. Children are consuming far too many more calories than they are burning in their day-to-day activities. Solutions must therefore deal with both sides of the equation.

On the consumption side, most parents and medical experts agree that TV advertising of high-energy and low-nutrition food is adding to ''food pressure''. Regulation of fast food advertising is certainly needed as one part of a co-ordinated response.

As a community, we also expect that high-profile and inspirational public figures, especially sports figures, play their part.

KFC is among Cricket Australia's main commercial partners. The company heavily promoted its ''tower burger'' during the Ashes campaign. Nutritional information about this product is not available on the KFC website. But an inquiry revealed it to contain 605 calories. A hash brown, cheese, mayonnaise and fried chicken burger represent about a third of a typical child's daily energy requirements, or two to three hours of continuous cricket.

Shane Warne's recent association with McDonald's is even more exasperating.

The ''Legend'' chicken burger was launched this summer, and again - despite eight pages of nutritional information on its website on everything from Big Macs to the type of water it sells - there was nothing from McDonald's on this product. Again, an inquiry elicited information: there are 588 calories in a burger with fried chicken, bacon, cheese and mayonnaise. With 34 per cent of an average adult's daily fat requirements and 66 per cent of one's daily sodium, this burger won't be getting a Heart Foundation tick of approval.

One of our most famous cricketers spruiking McDonald's during a match is really a low blow to kids and parents trying to favour healthy fresh food over fatty food consumerism.

The number of McDonald's and KFC advertisements every hour during the cricket is overwhelming. Rather than help reverse the ''obesogenic'' modern environment that has made Australia one of the fattest nations on earth, our cricket heroes appear content to make matters worse.

What's the alternative? Imagine the galvanising force and health promotional bonanza of our cricket heroes repudiating fast food sponsorship. It would be the talk of the nation, and no doubt grab the attention of many youngsters.

There is precedence, if not in the cricket world. Arguably the greatest football team on the planet, Barcelona FC, proudly promotes the United Nations children's charity UNICEF on its shirts, rather than any commercial organisation.

The ledger is, of course, not all bad for the Aussies. Sports stars, by nature, represent fitness, athleticism, excellence and teamwork - all worthy traits.

It is therefore an even greater shame that those with the best credentials for leading the charge against obesity in our schoolyards undermine their positive physical activity message by representing fast food. They can do better - and should - for our children's benefit. Who knows, it may even help with their on-field performance.

Dr Michael Valenzuela is a senior research fellow in the Faculty of Medicine, UNSW.

This article was first published on Fairfax's National Times website.