Lead author Dr. Y. Claire Wang of Columbia University's Mailman School of Public Health in New York said the study findings challenge criticism that the legislation is discriminatory against the poor.
Wang said the proposed New York City soda-size cap was approved by the New York City Board of Health and is currently under appeal after being struck down by the New York State Supreme Court in March.
The study used national data, but the researchers said the results were a strong validation of the obesity-prevention measure no matter where implemented.
Wang and co-author Seanna M. Vine analyzed 19,147 dietary records from 2007-10 for the demographics related to the consumption of sugar-sweetened beverages.
More than 50 percent of Americans consumed sugary drinks on a daily basis, but 7.5 percent purchased them from a food establishment in portions larger than 16 ounces on a given day.
The study, published in the American Journal of Clinical Nutrition, found the proportion was marginally higher in some groups: 8.6 percent of those who were overweight compared to 6.4 percent of those who weren't overweight, 13.6 percent of overweight teenagers and 12.6 percent of overweight young adults ages 20-44.
Americans with incomes less than 130 percent of the poverty line consumed large sugary drinks from food service establishments in equal proportion to those with higher incomes, the study said.
Given the uncertainties, the researchers said it was difficult to estimate how the policy would cut calories, but a reasonable assumption, would be 80 percent of large soda drinkers would downsize to a 16-ounce soda and 20 percent would buy two 16-ounce sodas -- cutting 63 calories daily.
Wang's earlier research found a reduction of 64 calories per day is needed to reach the country's Healthy People 2020 goal for reducing obesity.
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