UnitedHealth Group Inc. said its projected losses on the Affordable Care Act exchanges for 2016 deepened as enrollment grew despite the company’s efforts to reduce sign-ups.

The biggest U.S. health insurer said it is expecting losses of more than $500 million on its 2016 ACA plans, compared with previous projections that amounted to $400 million to $425 million in losses.

UnitedHealth had taken steps to pull back on its exchange business in anticipation of losses, including reducing marketing and slashing commissions to health-insurance agents.