UPDATE 2-UnitedHealth CEO Hemsley to step down, Wichmann succeeds

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Aug 16 (Reuters) - UnitedHealth Group Inc's Stephen Hemsley is stepping down after more than a decade as chief executive and will be succeeded by company veteran David Wichmann, the largest U.S. health insurer said on Wednesday.

Under 65-year-old Hemsley, UnitedHealth became one of the biggest sellers of insurance plans on the exchanges created as part of former President Barack Obama's national healthcare law.

However, mounting losses from the program prompted the company to largely exit from Obamacare plans in 2017.

Hemsley, who took over as CEO in 2006, will now take on the newly created role of executive chairman. Wichmann, 54, has spent nearly 20 years with the company and has formerly served as its chief financial officer.

The insurer reported a better-than-expected quarterly profit last month, helped by its decision to abandon the Obamacare individual insurance market, amid uncertainty over the fate of the law under President Donald Trump's administration.

Hemsley said in July he was optimistic about the business next year, but that national and state healthcare policies would be a possible drag on profit in 2018. Shares of the company have risen nearly four-fold since Hemsley took over the helm.

UnitedHealth on Wednesday also said Chairman Richard Burke would be appointed lead independent director. Both Hemsley and Burke will take on their new roles on Sept. 1, the company said.

UnitedHealth's shares were up 1.2 percent at $196.89 in light premarket trading on Wednesday. (Reporting by Akankshita Mukhopadhyay and Tamara Mathias in Bengaluru; Editing by Maju Samuel)