Wendy’s rejected a $1.4 billion buyout offer from an activist investor, saying Thursday that the bid was too low, and it adopted a “poison pill” plan that would make it more difficult to engineer a hostile takeover of the company.

Noted investor Nelson Peltz made an offer last week to buy the chain, which has been struggling with high beef prices and aging stores. Peltz said the fast-food landscape had become increasingly challenging, with consumers under pressure, intensifying competition and persistent inflation, and his offer was the best path forward for shareholders.

But in a conference call with investors Thursday, Wendy's CEO Bob Wright, who joined the company in May from Potbelly, said Wendy's has a turnaround plan in place that is already producing good results.

“We’re confident that we have the right strategy, execution and resources to restore Wendy’s to its full potential and drive meaningful shareholder value,” Wright said.

Shares rose more than 2% Thursday as the company reported a better…