Taxing sweetened drinks such as pop and limiting junk food ads for children could help curb obesity worldwide, researchers say in a medical journal series.

This week's issue of the Lancet includes a series on trends in obesity, which increases  the risk of heart disease, stroke, Type 2 diabetes and some cancers.

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By taxing sugar-sweetened beverages, governments could make it easier for children to make healthy choices, researchers say. (iStock)

"By imposing tax on sugar-sweetened beverages and limiting marketing of unhealthy foods to children, governments can lead in making it easier for children to make healthy choices," said the lead author of one of the papers, Steven Gortmaker, a professor of the practice of health sociology at Harvard School of Public Health.

Increasing taxes and marketing restrictions have helped in tobacco control and likely would work in reducing consumption of sugar-sweetened drinks, the researchers suggest.

Obesity is often defined in terms of the body-mass index or BMI, a measure of heights and weights. In adults, a BMI of 30 or more is considered obese.

A second paper in the series projected that if present trends continue, about half of men and women in the U.S. will be obese by 2030.

Some 32 per cent of men and 35 per cent of women are now obese in the United States, Claire Wang at the Mailman School of Public Health in Columbia University in New York and her co-authors said.

In Britain, obesity rates are projected to be between 41 to 48 per cent for men and 35 to 43 per cent for women by 2030, up from 26 per cent for both sexes now.

"An extra 668,000 cases of diabetes, 461,000 of heart disease and 130,000 cancer cases would result ," for the U.S. and U.K. combined, Wang's team wrote.

Beyond compromising the healthy, productive lifespan of populations, the increases in obesity could add an estimated $48 to $66 billion US a year in the U.S.