While working with Burger King, Adar said he's even had to sign a legal document saying he didn't alter anything. Chick-fil-A demanded that he use its procedures.
"Most companies today want it to be fresh, natural, not overworked," Adar said.
McDonald's, Burger King, Starbucks, Chipotle and Yum Brands didn't respond to CNBC email requests for comment about the practice of food styling. A Chick-fil-A spokeswoman said the company isn't sure it would "be a fit for this story" since it takes a different approach to using food in its commercials, which often center on cows advising people to 'eat mor chikin.'
A Wendy's spokesman said about food stylists, "We supply the same ingredients to them as our restaurants receive. We also require that they prepare and build the products to operational procedures. The big difference is how much time we take to get an appealing shot."
In a statement, Dunkin' Donuts Spokeswoman Michelle King said, "Dunkin' Donuts always uses real Dunkin' Donuts product in our advertisements. Our shoot director and food stylist team build the products to the exact specifications provided by Dunkin' Donuts' chefs to match what will be sold in our restaurants. We strive to ensure the authenticity of our products in our advertising."
On the regulatory side, Federal Trade Commission spokeswoman Betsy Lordan told CNBC by email that truth in advertising laws do apply to restaurant menu items displayed in ads. The commission examines both what's implied by and stated in an ad to determine whether it's deceptive.
"There are no specific FTC regulations governing food photos used in advertising, and the FTC has not pursued any cases alleging that food ads are deceptive based only on the photos," she wrote.
If, for example, customers see that McDonald's fries look different in person than in an ad, that would not cause the same regulatory concern as a false claim that a product has special properties, like reducing the risk of illness.