Obamacare enrollment was down in 2015 for one of the biggest insurers in the country, and so were profits in the last quarter of the year.

Enrollment in 2015 for Anthem's individual business, a majority of which comes from Obamacare's marketplaces, was down 6.6 percent from 2014, the company's financial statement said on Wednesday. At the same time, profits in the fourth quarter of 2015 dropped by 64 percent compared to the fourth quarter in 2014, with the cost to provide care to Obamacare enrollees making an impact.

Anthem's total enrollment in Obamacare is about 800,000 people, and the insurer estimates that figure will decline further in 2016 by about 300,000 people.

"Unsustainable pricing in some markets is hurting our market share," CEO Joe Swedish said in a conference call Wednesday. "We are encouraged that early indicators in open enrollment activity are slightly better than our expectations."

Obamacare's open enrollment period ends on Sunday, and so far about 11 million people have signed up for it.

The insurer hasn't just had problems with fewer enrollees, but also with the costs for those in the exchanges. Anthem's benefit-expense ratio, which is the cost for providing care versus the money Anthem collects from premiums, was 87 percent in the fourth quarter of 2015. This is an increase from the 84.5 percent in the fourth quarter of 2014.

Anthem attributes the increase to the individual and local group marketplaces. It was partially offset by cheaper costs in the Medicare marketplaces.

Swedish said the administration's decision to eliminate several special enrollment periods, which allow people to sign up for Obamacare year-round, could help contain costs. The one-year moratorium on the health insurer tax included in Congress' latest budget deal is also very helpful, he said.

Insurers want as many enrollees as possible to sign up during open enrollment. If someone signs up when he gets sick and then drops out when he feels better, it leads to higher costs for the insurer.

Anthem's results come as other insurers are either posting financial losses in the individual marketplace, which represents people who don't get insurance through work, or no profit.

UnitedHealth, the country's largest insurer, said this month it lost $720 million in the individual marketplace in 2015. UnitedHealth last year flirted with leaving the marketplaces, causing insurance stocks to plummet.

Anthem was one of several insurers who said it remained committed to the exchanges.

The insurer was able to offset the losses in enrollment in its individual business with the increase in Medicaid enrollment, which went up by 721,000 members in 2015.

Anthem serves about 38 million members and earned $2.6 billion in profits last year, the same total as in 2014.