The letter -- signed by Emanuel, as well as New York Mayor Michael Bloomberg and Boston Mayor Thomas Menino, among others -- was sent Tuesday to House Speaker John Boehner, R-Ohio, and Minority Leader Nancy Pelosi, D-Calif., the Chicago Tribune reported.
The mayors said the Supplemental Nutrition Assistance Program -- commonly known as food stamps -- "can do more to address the pressing challenge of obesity and diet-related disease."
"It is time to test and evaluate approaches limiting SNAP's subsidization of products, such as sugar-sweetened beverages, that are contributing to obesity," the letter said.
Tom Alexander, a spokesman for Emanuel, said the letter calls for Congress to provide incentives for food stamp recipients to eat healthier.
"The letter, which was signed by 18 mayors, urged Congress to incentivize healthy food and beverage options under the SNAP program -- the same thing we do in city government, having moved completely to healthy vending machines, and through our food access initiatives throughout Chicago," Alexander said in an e-mail. "We are not limiting options, but are incentivizing healthy choices."