Canada's obesity epidemic needs legislative approaches such as taxing junk food, setting standard portion sizes and nutritional labels, and banning trans fat, researchers say.

"Obesity is expected to surpass smoking as the leading cause of preventable morbidity and mortality," Dr. Mark Eisenberg of Jewish General Hospital and his co-authors wrote in Tuesday's issue of the Canadian Medical Association Journal.

The authors argue that a public health approach is needed to fight obesity in both adults and children, and its toll on life expectancy when combined with heart disease, high blood pressure, stroke, Type 2 diabetes and other illnesses.

"Legislative approaches, together with environmental modifications, can be an effective means of reversing the growing problem of obesity in Canada," the authors say.

They discuss the advantages and disadvantages of legislative approaches including:

• A tax on junk food, saying it remains unclear whether such a tax is feasible or appropriate.
• Improved nutritional labels, such as the U.K.'s "traffic-light system" of voluntary red, green and amber colour codes to indicate the nutritional value of foods, combined with educational programs.
• Clearly defined serving sizes to compare products more easily and reflect "real-world" portions.
• A ban on trans fats and regulation of sodium content.
• Modifying neighbourhoods to provide opportunities for safe physical activity, such as providing well-lit sidewalks and bicycle paths.
• Zoning bylaws to regulate the number and density of fast-food restaurants and their distance from schools and hospitals or to ban them from specified areas and neighbourhoods.
• Requiring restaurants to display calorie counts on menus to increase awareness and influence consumer choice.
• Banning advertisements for unhealthy foods, though the researchers say the link between the ads and poor health outcomes is still unclear.
• Banning the sale of junk food in schools.

Obesity has traditionally been viewed as a physical problem for doctors to treat, but there is an increasing awareness of the role that governments, corporations and educators can play in preventing and reducing the problem, the researchers say.

"The growing problem of obesity in Canada can be reversed only with an integrated approach involving both the public health and medical models," the authors conclude.

"There is a greater need than ever for strong political will to effect these complex societal changes, and for champions at all levels of government to step forward and do so in new, innovative and effective ways."