Body dissatisfaction is a problem that disrupted various areas of the individual's life and caused psychological effects such as depressive symptoms, anxiety, and malfunction in certain areas of life. Body dissatisfaction itself is a trajectory that begins as a teenager and peaks at the age of early adulthood. Body dissatisfaction is a psychological phenomenon that is significantly influenced by social factors, such as age, ethnicity, socioeconomic status, sexuality, media, family and friend, and BMI. Young adulthood is a period where individuals begin to build personal and economic autonomy, think about careers, choose a partner and start marital life. One of the developmental tasks in this stage of life is choosing a spouse where body shape often associated with sexual attractiveness. It can be said that young adult women who have a perception that their body shape is less satisfied they will consider themselves as less attractive. They believed that that situation making it difficult for them in getting a life partner. Acceptance and Commitment Therapy (ACT) is a technique of psychotherapy that aims to train "acceptance" of a condition or event that has been avoided, fully awareness making a commitment to take action to achieve a better life. Referring to the previous study, Brief-ACT was significantly lowering anxiety level to the body and distress due to weight-related thinking.

This study is a pre and post-test study that used the PASTAS-S as a screening tool to determine the changes that occur after the intervention. The PASTAS-S has never been adapted into the Indonesian version. Before using PASTAS-S, validity test was performed first by using BUT-A as a criterion. The sample in this study was young adult women who undergoing lectures at Universitas Indonesia. The implementation of brief ACT intervention was conducted in group settings where consisting of 4 peoples in a group and it had 4 sessions that divided into 3 meetings.

The result of the study found that Brief-ACT in groups setting that performed in 4 sessions decreased body dissatisfaction in young adult women. From the scores that obtained in pre and post-test we got an information that there was a reduction of body dissatisfaction level. The scores among five participants were in the range of 0.3 to 1.19 points out of 4.

Brief-ACT in groups setting helped lowering body dissatisfaction levels in young adult women. A total of 5 participants who participated in 4 sessions divided into 3 meetings showed a reduction in body dissatisfaction level. Among 5 participants, a significant decline was seen in two participants (named RI and KHD) with a distinction score of PASTAS-S at minimum 1. Moderate decline seen in 1 participant (named DI) that had the difference of score above 0.5, while other participants (named IS and NB) showed differentiation of score below 0.5. Thus, it can be said that brief ACT intervention in group setting could lower body dissatisfaction in young adult women. This intervention is effectively used in participants with above-average BMI as well as with minimal early moderate anxiety levels.

Keywords: body dissatisfaction, early adulthood, Brief-ACT, groups.