7 trillion calories each year is the average American child's consumption from liquid sugar alone, says health professor, suggesting that sweet drinks are a major factor to rising childhood obesity rates. An estimate of 12.5 million (17 per cent) of U.S. children are obese; three times as much as thirty years ago.

The figures sound alarming when calculated together: The estimated 270 calories that each child consumes from sugary drinks amount to over 19 billion calories a day nationwide. Dr Steven Gortmaker, Director of the Harvard School of Public Health Prevention Research Center, is pushing for an increased involvement of the government to protect children from sodas and other drinks containing large amounts of sugar.

For children, the daily recommended amount of calories ranges from 1,200 to 2,200, depending on age and gender, which means that sugary beverages account for 15 to 25 per cent on average.

'During the past 30 years, the consumption of sugar-sweetened beverages has increased dramatically. Compelling evidence supports a positive link between the consumption of sugar-sweetened beverages and the risk of obesity,' the authors of the academic paper, Sugar-Sweetened Beverages and Genetic Risk of Obesity, wrote.

Dr Gortmaker suggests that already allowing kids fewer options of sugary beverages at schools reduces the average calorie consumption by 45 calories. This might already be enough to turn the trend to obesity around, he says.

Read also: Childhood Obesity: Beverage Lobby Hits Back Saying Sugary Drinks Are Not Only Factor