The finding came from a study of 390 German women who were using one of two diet plans. The simpler plan provided shopping lists for dieters and a meal plan they were to follow. The more complex plan assigned point values to every food and instructed participants to eat only a certain number of points each day.

The women completed questionnaires over an eight-week span.

"For people on a more complex diet that involves keeping track of quantities and items eaten, their subjective impression of the difficulty of the diet can lead them to give up on it," Peter Todd, a professor in the department of psychological and brain sciences at Indiana University, said in a university news release.

The effect endured even after the researchers accounted for the influence of significant social-cognitive factors such as self-efficacy -- people's belief that they're capable of achieving a goal, such as adhering to a diet regimen to lose weight.

"Even if you think you can succeed, thinking that the diet is too cognitively complex can undermine your efforts," the study's co-author, Jutta Mata, a psychology professor at Stanford University, explained in the news release.

The study was published online in Appetite.

Mata suggested that people considering going on a diet should look at a number of diet plans and consider how many rules a plan has and how many things a dieter needs to keep in mind while using the plan.

"If they decide to go with a more complex diet, which could be more attractive, for instance, if it allows more flexibility, they should evaluate how difficult they find doing the calculations and monitoring their consumption," she said. "If they find it very difficult, the likelihood that they will prematurely give up the diet is higher, and they should try to find a different plan."

• Do Low-Carb Diets Really Work?