Kaiser Foundation Health Plan and Hospitals muscled up to produce improved income and revenue for its third quarter — but the health care titan also said membership dwindled in a brutal economy.

Oakland-based Kaiser generated net income of $569 million, which reversed a year-ago third-quarter loss of $399 million.

Kaiser's operating revenues totaled $10.5 billion in the third quarter, which was 2.9 percent higher than the $10.2 billion in revenue a year ago.

"We are pleased with our performance," said Kathy Lancaster, Kaiser's chief financial officer. Nevertheless, Lancaster added, "We continue to focus on making our high-quality care and service as affordable as possible, which is especially important to our customers and members in this uncertain environment."

Despite these positive results, a slump in membership haunted the health care giant.

Over the first nine months of 2009, membership fell by 63,000 and now totals 8.58 million, Kaiser said. Since the end of 2008, total membership has fallen 0.