UnitedHealth Group Inc., the nation’s largest health insurance firm, has announced it plans to withdraw from all but “a handful” of Obamacare states in 2017 as it faces losses from the program rising to $650 million this year.

UnitedHealth currently insures 795,000 Obamacare enrollees in 34 states, but CEO Stephen J. Hemsley says “the shorter-term, higher-risk profile” of most of these enrollees makes it difficult to continue insuring them. (Translation: older, sicker, costlier enrollees.)

In light of the UnitedHealth announcement, a spokesperson for the Department of Health and Human Services (HHS) told the Wall Street Journal that “the marketplaces will continue to thrive for years ahead” despite the defection of the nation’s premier insurer.