WASHINGTON — The Obama administration plans on Wednesday to propose expanding Medicare to cover programs to prevent diabetes among millions of people at high risk of developing the disease, marking the sixth anniversary of the Affordable Care Act with the prospect of a new benefit, federal officials said.

Sylvia Mathews Burwell, the secretary of health and human services, is scheduled to announce the proposal at a Y.M.C.A. here. Under the plan, Medicare would pay for certain “lifestyle change programs” in which trained counselors would coach consumers on healthier eating habits and increased physical activity as ways to prevent Type 2 diabetes, formerly called adult onset diabetes. Such programs have been found effective in people with a condition known as prediabetes, meaning that they have blood sugar levels that are higher than normal but not high enough to be considered diabetes.

That expansion was made possible by provisions of the Affordable Care Act, which President Obama signed six years ago Wednesday.

The Centers for Disease Control and Prevention estimates that 86 million adults, including at least 22 million people 65 or older, are prediabetic, increasing their risk of heart disease, stroke and diabetes itself.