(Adds context on exchanges)
June 11 (Reuters) - Health insurer Aetna Inc is submitting premium rates to regulators for Obamacare insurance plans for 2015 that generally increase less than 20 percent from 2014, its Chief Executive Officer Mark Bertolini said on Wednesday.
Bertolini's comments, made during a Goldman Sachs healthcare conference outside Los Angeles, come as insurers prepare next year's health plans for the insurance exchanges created under the Affordable Care Act, known as Obamacare.
About 8 million people have signed up for these plans, which are provided by commercial subscribers and come with income-based government subsidies.
While Aetna and other insurers say they have lost money providing these plans this year, insurers are expanding into new markets for 2015 to capture a growing customer base.
Bertolini said about half the rate of increases the insurer has submitted for 2015 were due to changes in Obamacare.
Over the past year, President Barack Obama's administration has made such changes to the law as allowing some plans that had been due to phase out this year to remain in place. That has changed some of the assumptions that determine premium rates.
Bertolini had predicted rate increases along these lines in April when he announced the company's first quarter earnings report.
In addition, the company expects about 450,000 exchange customers at year end, in line with his previous outlook, Bertolini said during the presentation to investors.
Aetna is one of the largest players on the exchanges, along with WellPoint Inc.
Bertolini said the 2014 outlook takes into account that Aetna customers were disenrolling from exchange plans on a regular basis. While he didn't know why they were leaving, he suspected it was due to out-of-pocket costs before members reach their deductibles.
(Reporting by Caroline Humer; Editing by Chris Reese and Bernadette Baum)