Hamburger chain Wendy's Co (WEN.O) will buy back $1.4 billion of shares, including $211 million from Nelson Peltz's Trian Group, its largest shareholder, in its biggest repurchase program.

Trian said the sale of shares is part of its plan to reduce stake in Wendy's to 17.0-19.7 percent in the "next few months" from 24.8 percent to "avoid adverse federal income tax consequences."

Wendy's shares rose as much as 5.5 percent to an over seven-year high of $11.71 on Wednesday.

The company launched an $850 million share buyback program. It aims to complete the total buyback program by the end of 2016.

Trian plans to reduce its holding in Wendy's by at least 20 percent by selling shares in the buyback program as well as in the open market or through privately negotiated deals, the hedge fund said in a regulatory filing. (1.usa.gov/1BKvV8j)

Wendy's had 363.5 million shares outstanding as of May 29. On this basis, Trian holds about 90 million shares in the restaurant chain.

Peltz, a non-executive chairman on Wendy's board, has held a stake in the company since 2005.

Wendy's also adjusted its full-year earnings forecast to reflect the sale of its bakery operations.

The company said it expected 2015 adjusted earnings of 31-33 cents per share, excluding about 2 cents per share attributable to its bakery operations.

Wendy's received after-tax proceeds of about $50 million from the sale of its bakery operations, which was announced in May.

The company's shares were up 4.5 percent at $11.60 in late morning trading on the Nasdaq.