A new study says that planning your diet would not actually help you gain self-control unless you are feeling good about your weight in the first place.
And the same goes for saving money.
"Although planning tends to aid subsequent self-control for those who are in good standing with respect to their long-term goal, those who perceive themselves to be in poor goal standing are found to exert less self-control after planning than in the absence of planning," write authors Claudia Townsend (University of Miami) and Wendy Liu (University of San Diego).
The authors found that making a concrete plan for implementing goals creates emotional distress for people who believe they are in poor standing with respect to their goals.
This, in turn, undermines their motivation for self-regulation.
In five studies, the authors randomly assigned participants to a planning or no planning condition.
In the diet studies, the people in the planning condition were asked to plan their diet and food intake for the rest of the day, while those in the non-planning condition did not.
Then all the participants were offered a snack. In some studies, participants chose between raisins or a candy bar.
In another study, the choice was between cookies or no snack at all.
"What we found was among respondents who felt good about their weight, planning led to healthier choices-choice of the healthier snack in the first case or no snack in the second choice," the authors wrote.
"However, the surprising result was that among respondents who did not feel good about their weight (considered themselves overweight), those who planned were actually more likely to select the unhealthy snack in the first case or cookies in the second case."
This effect also held true when it came to financial planning.
When they received a tax rebate, consumers who were confident in their savings were less likely to spend the rebate after planning than in the absence of planning.
And people who were not confident in their spending were more likely to spend the rebate money after planning.
"Generally, people assume that planning will help for goal attainment," the authors wrote.
"But this research suggests that having a positive self-view is just as important, if not more so," they added.
The study has been published in the Journal of Consumer Research.