A move to cover expensive weight-loss drugs for Americans on Medicare and Medicaid may be in the works, but any such program could run into problems with voluntary participation and concerns about expense.

The federal government is expected to start a 5-year-long experiment that will provide some limited coverage of obesity medications.

According to the Washington Post, 13 states currently cover the drugs for Medicaid patients, while Medicare prohibits coverage of the drugs used solely for weight loss, but allows for treating indications they are approved for like sleep apnea and heart disease.