Is America finally saying no to junk food?

It's been a tough year for purveyors of fattening foods. Although the economy continues to recover and people have more money to spend, they aren't spending it on sugar, carbs and empty calories.

And that's hurting the earnings of companies that for decades have reliably counted on Americans to consume all kinds of fried, salty and sugary treats. Shares of Dunkin' Brands (DNKN) were down nearly 6 percent Thursday after the chain disappointed Wall Street's revenue expectations and warned that growth is slowing.

Dunkin' Brands owns Dunkin' Donuts and the Baskin-Robbins chain of ice cream shops. Its shares have fallen nearly 8 percent this year.

McDonald's (MCD) is also stumbling, and Tuesday reported slumping sales and profit in the third quarter. The company said it needs to make major changes to its business to survive. Shares have fallen more than 5 percent this year.

Coca-Cola (KO) saw 14 percent less profit in its recent quarter as global soda sales remain flat. The company said its earnings per share this year will miss its long-term goal of high-single-digit growth. Shares are down less than 1 percent this year.

Do the misfortunes of all three companies reflect a growing distaste for unhealthy food? Not exactly, said Howard Penney, managing director at Hedgeye Risk Management. Penney researches the restaurant industry and consumer staples sectors in the U.S.

"People are definitely trying to eat healthier, there's no doubt about it. But I think that each company has its own individual issues," Penney told CBS MoneyWatch.

He pointed to Sonic (SONC) as an example of a fast-food company that's doing well. The drive-in burger chain recently beat Wall Street expectations for its fiscal fourth quarter, though its revenue, at $163.8 million, is a small fraction of McDonald's and Dunkin' Brands' sales. Shares of Sonic have risen more than 20 percent this year.

Penney said it's easy to blame McDonald's problems on Millennials and other diners going to Chipotle Mexican Grill (CMG) and other rivals. But the company's troubles "are so much bigger than that," he added.

For example, McDonald's and Dunkin' Brands have been very aggressive with increasing the number of items on their menus, he added. That can backfire. "Broadening out a menu and making it more complex can hurt operations," he said.

In its quarterly earnings release, Dunkin' Brands blamed "ongoing challenges with the economy" and intense competition from rivals to get the breakfast crowd.

Rather than spurning unhealthy food and beverages, Americans may be seeking out dining options they perceive as being of higher quality. It's a fine distinction. Analysts say Chick-fil-A, for example, could rise to become one of the top fast-food chains in the country over the next decade. And Dunkin' Brands may see new competition from the growing trend toward gourmet doughnuts.

Coca-Cola has been trying to emphasize its noncarbonated brands, which include Minute Maid fruit juices, Dasani water and Powerade sports drinks. The company blames weak consumer spending and economic upheaval across the world.

"I don't see that improving overnight," CEO Muhtar Kent told analysts in a conference call this month. "I think it's a new normal."