Objectives: Maternal nutritional behavior before and during pregnancy contributes significantly to improving the outcomes of pregnancy and the health of the newborns after birth. In addition, the theory of planned behavior (TPB) is a proper model for use during pre-pregnancy and pregnancy. Therefore, the present study evaluated the effect of TPB education on nutritional behaviors of overweight and obese women before pregnancy.

Materials and Methods: This randomized controlled trial was conducted on 100 overweight and obese women who attended a nutrition unit in Khansar during April-August 2017. A convenient sampling method was used and the samples were randomly divided into intervention and control groups. The intervention group participated in five nutritional training sessions based on the TPB in addition to routine care. Data were collected with TPB and nutritional behaviors questionnaires before, after, and 2 months after education. Finally, the Student’s t test, Fisher exact test, as well as Mann-Whitney U test, chi-square and repeated-measure tests were utilized for data analysis.

Results: Based on the result of the repeated measure test, the overall score of the TPB changed (P = 0.002) over time and a significant difference was observed between the 2 groups (P = 0.002). In addition, the result of the repeated measure test indicated that the length of time affects the nutritional behavior score (P = 0.000) and there was a significant difference between the 2 groups in this regard (P = 0.000).

Conclusions: Considering the effect of training, based on the TPB, on nutritional behavior, the content of this training is suggested to be included in the pre-pregnancy program.