Obesity is on a rampage in the western world, but developing nations are fast catching up. Health officials gathered at an international conference in Sydney are calling for governments to step in to reverse the pandemic.

There are now more overweight than undernourished people in the world, he said.

Zimmet, an Australian diabetes expert who is a professor at Monash University, tagged the international crisis "globesity."

Among the repercussions of the obesity pandemic among adults and children are skyrocketing rates of chronic ailments such as diabetes and heart disease, and, ultimately, shorter life spans. The current generation of children could be the first in history to die before their parents because of health problems related to weight, said Kate Steinbeck, an expert in children's health at Royal Prince Alfred Hospital in Sydney.

The economic burden associated with treating health problems connected to obesity -- immeasurable on a global scale -- threatens to overwhelm national medical systems, Philip James, chairman of a global task force, reportedly warned.

More than 1 billion adults around the world are overweight and 300 million are obese, says the World Health Organization. In contrast, the number of people who are undernourished is estimated at 800 million.

Childhood obesity is a particular worry. Globally, 22 million children under five are estimated to be overweight, notes WHO.

In the US, the number of overweight children has doubled and the number of overweight adolescents has tripled since 1980, according to the Surgeon General.

Although overeating -- particularly energy-dense foods high in saturated fats and sugars -- and inactive lifestyles are more prevalent in the world's wealthier countries, these twin causes of obesity are quickly becoming drivers of the pandemic in the developing world as well, WHO reports.

In addition to diabetes and heart disease, obesity hikes the risk of high blood pressure, strokes and some forms of cancer. It also contributes to psychological problems such as low self esteem and depression resulting from the social stigma of being overweight.

Delegates at the conference acknowledged that attempts to persuade individuals to change their diet and exercise habits have failed. Some called for governments to intercede by banning junk food ads that target children, but they acknowledged the political difficulties in pursuing such approaches.

Health officials are calling on governments to require more parks, bike paths and sidewalks in new housing development plans.

"We know this is not about gluttony -- it is the interaction of heredity and environment," Zimmet said. "We know that small changes can make a big difference in people's weight and health."

Approximately 400 health experts will make presentations to the conference before its close on Friday.