That extra can of soda each day equals 15 pounds extra in weight

A scientific review says what they are drinking is what is making Americans obese.

According to the new report the average American is drinking far more soda and other sugary drinks than ever before and that is why people have gained weight.

The researchers say that an extra can of soda a day can add 15 pounds in weight in a single year, and they suggest that this increased consumption is a key factor in the obesity problem.

Dr. Frank Hu, who led the report says they looked at the big picture rather than individual studies and it is clearly justifiable in public health terms, to limit sugar-sweetened beverages.

Hu and a team at the Harvard School of Public Health reviewed the most credible scientific nutrition studies conducted over the last 40 years.

The work was conducted with support from the American Heart Association and various federal agencies.

The study found that one-third of all carbohydrate calories in the American diet come from added sweeteners, and the sweeteners in beverages account for half of those calories.

The blame it seems lies with the most common sweetener used in soft drinks, high fructose corn syrup which not only contains more calories than regular refined sugar, but some studies suggest it reduces the body's ability to process calories.

The researchers say the increased availability of soft drinks has also been a contributing factor.

However the American Beverage Association says that not all studies have concluded that just beverages are to blame for obesity and the review has over-looked those that have discounted such a link.

The Association says blaming one specific product or ingredient as the root cause of obesity is not common sense as there there are many contributing factors, including regular physical activity.

Some experts on obesity disagree and say there is an overwhelmingly strong case to be made for a causal relationship between obesity and beverages.

The review says a single 12-ounce can of soda provides the equivalent of 10 teaspoons of table sugar.

In all, 30 studies were reviewed representing a range of methods and types, and even though not all showed the harm of beverages, they collectively suggest that soda and sugary drinks "should be discouraged, say the authors.

U.S. federal dietary guidelines recommend beverages without added sugars, and the World Health Organization advises that added sugars should provide no more than 10 percent of total calories.

More and more often sugary drinks are now being restricted in schools and following prompting by people such as Bill Clinton, himself a confessed former fat boy, in May, top beverage distributors agreed to stop selling non-diet sodas in certain schools and restricted sales in certain settings where young children buy them.

The report is published in the American Journal of Clinical Nutrition.