"If we're going to fix health care, we've got to get at the delivery of care and the cost of care," Bertolini said in a "Squawk Box" interview. "The ACA does none of that. The only person who's really going to drive that is the consumer and the decisions they make."
Aetna said Tuesday that its medical spending rose more than estimates in the second quarter, due in part to the higher costs of covering patients who bought insurance under Obamacare for the first time. But the third-largest U.S. health insurer also reported better-than-expected earnings and revenue in the second quarter and raised full-year guidance.
"We have more people in the system using health care. So if you have coverage you are going to use it, particularly if you haven't had coverage before and have pent-up demand," the Aetna CEO explained. "Usually utilization and health care [also] pick up as the economy recovers, people get back to work and they get more coverage."
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But Aetna expects medical spending this year to be at the low end of its forecasts and said the second quarter does not represent a new upswing after years of slowing growth in health costs.
Last week, two federal appeals panels disagreed on the legality of Obamacare subsidies that gave billions of dollars to help 4.7 million people buy insurance on HealthCare.gov. While this issue could end up before the Supreme Court, the subsidies for now remain in effect.
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"We have 600,000 ... customers as a result of the Affordable Care Act," Bertolini said. "We do know they are sicker. We know 87 percent are subsidized. We know they are older. So we expect they are going to use more health care."
"We priced this [Obamacare] business at lower margins in the 3 percent to 5 percent range … but we didn't plan or expect earnings as a result of those populations," he explained.
Going beyond Obamacare, Bertolini said: "We have to redesign the underlying system, but we have to engage consumers in different ways."
Aetna has found, he said, that when private employers move to private health exchanges and give workers a choice, the employees of those companies buy more a cost-effective health care product because "it's their money to spend versus their employer buying it for them."
—By CNBC's Matthew J. Belvedere. Reuters contributed to this report.
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