Many people signing up for 2016 health policies under the Affordable Care Act face higher premiums, fewer doctors and skimpier coverage, which threatens the appeal of the program for the healthy customers it needs.

Insurers have raised premiums steeply for the most popular plans at the same time they have boosted out-of-pocket costs such as deductibles, copays and coinsurance in many of their offerings. The companies attribute the moves in part to the high cost of some customers they are gaining under the law, which doesn’t allow them to bar clients with existing health conditions.