"The nutritional quality of her diet can't be very good," said Baye, of Medical College of Georgia Hospital. "Yeah, you might lose the weight, but you're certainly not going to be healthy."
Though the idea of the fast-food Mexican restaurant serving as a nutritional beacon seems ludicrous to some, there are ways to eat better in those places and, just as importantly, simple things to avoid when choosing seemingly healthier alternatives.
The Taco Bell ads feature a woman identified as Christine, who chose items that evidently are lower in calories and fat than some other menu items. She lost 54 pounds over two years by lowering her fat intake and reducing her consumption by 500 calories a day, according to the campaign's Web site.
Taco Bell offers seven items with 8 grams of fat or less, though three of them have more than 300 calories apiece. The program also has a big disclaimer: "Drive-Thru-Diet is not a weight-loss program. For a healthier lifestyle, pay attention to total calorie and fat intake."
That, experts say, is the key. "It is all about quantity and portion size," Baye said.
More restaurants appear to be catering to those who want to limit calories and fat by offering healthier alternatives. That can be a good thing, said Dr. Charles Stuart Platkin, the creator of DietDetective.com.
"I think it does help to make a difference," he said. "People might make better choices if they have the choice to start with. At least it is a starting point."
Listing calorie counts on menus has been shown to help those who are concerned about it, but it is unclear whether everyone is paying attention, Platkin said.
"The research isn't supportive that a lot of people do," he said.
Even restaurants such as Subway that tout healthier fast food can be traps. Some studies showed that people who went there often consumed more high-calorie side dishes or ate more than intended, said Dr. Jennifer L. Harris of the Rudd Center for Food Policy and Obesity at Yale University.
"We think there is kind of a 'health halo' effect that makes people feel better about going there, and then they end up eating more," she said.
It is important to pay attention to the details, especially when looking at the ads for these healthier alternatives, Baye said.
"When they say it is 100 calories, make sure you read the little fine print that says there is no cheese on this sandwich; there's no mayonnaise," she said.