The snack food giant Mondelez International, maker of Oreo cookies and Ritz crackers, said on Wednesday it had appointed Dirk Van de Put as its new chief executive.

Mr. Van de Put, the head of the frozen food company McCain Foods, will succeed Mondelez’s current C.E.O., Irene Rosenfeld, who will step down in November.

Mr. Van de Put’s appointment comes as big snack food makers struggle to adapt to changing consumer tastes and demands. Americans buy billions of dollars in chips, cookies and other treats every year, but are increasingly eschewing ingredients perceived as artificial. Last year, Mondelez introduced its first new product in years – Good Thins crackers, made with powdered sweet potatoes and chickpeas.

Mondelez’s revenue in its most recent quarter was down 5 percent from the same period a year earlier, to nearly $6 billion, and its share price is down 2.3 percent so far this year.

Since being spun off from Kraft Foods in 2012, Mondelez has also faced pressure to cut costs and improve profit from two of its activist shareholders, Nelson Peltz’s hedge fund, Trian Fund Management, and Pershing Square Capital Management, led by William A. Ackman.

Mr. Peltz, who joined Mondelez’s board in 2014, had been a particularly vocal agitator. Describing the “slow growth” of Mondelez’s beverage unit, Mr. Peltz had, at one point, pushed for a merger with PepsiCo and an eventual spinoff of the beverage division – a plan that he ultimately dropped.

Through a spokeswoman, Mr. Peltz said that he was “pleased” with the appointment of Mr. Van de Put, and praised Ms. Rosenfeld’s leadership, pointing to the growth in the company’s share price since she joined in 2006. In midday trading on Wednesday, shares of Mondelez were flat, at $43.72.

Irene Rosenfeld, Mondelez’s current chief executive, will step down in November. She will continue in her role as chairman of the board until March.

“Her leadership has benefited all of the company’s stakeholders,” Mr. Peltz said.

A spokesman for Pershing Square declined to comment.

Mondelez has faced challenges that have affected the industry as a whole, leading to consolidation and executive changes at some of the world’s largest food companies. In 2015, Kraft Foods merged with Heinz, a major bet on packaged and processed foods like Kool-Aid, Velveeta and Lunchables at a time when such items were losing ground to more natural options.

Last year, Mondelez attempted to buy the chocolate maker Hershey Company, but dropped those efforts in the summer.

Mr. Van de Put will also join the company’s board of directors. Ms. Rosenfeld will continue in her role as chairman of the board until March, when Mr. Van de Put will take on the additional role of chairman.

Mondelez declined to make Mr. Van de Put available for an interview.

Mr. Van de Put spent six years as the head of McCain, one of the world’s largest makers of frozen potato products, during which time the company said that it experienced record growth. McCain, a privately held company based in Canada, generates more than $9 billion in annual sales, according to its website.

In a statement, McCain said that its current chief financial officer, Max Koeune, would succeed Mr. Van de Put. A spokesman for the company declined to comment further.

Before McCain, Mr. Van de Put served in executive roles at the drug maker Novartis, the candy maker Mars and the Coca-Cola Company.

“He is a seasoned global C.E.O., having lived and worked on three different continents, with deep experience and expertise in all critical business and commercial operations in both emerging and developed markets,” Ms. Rosenfeld said in the announcement.