(Reuters) - Lamb Weston on Thursday appointed insider Michael Smith as its chief executive after pressure from activist investor Jana Partners to make changes to its top executives or sell itself.

Shares of the frozen potato snacks maker were down 13% in pre-market trading as it also cut its annual profit and sales forecasts.

Smith, currently the company's chief operating officer, will take over from Thomas Werner on Jan. 3, the company said in a statement.

Activist investor Jana Partners disclosed about a 5% stake in the company two months ago and has asked Lamb Weston to improve operations or consider selling itself.