Perbedaan proporsi perilaku pencegahan obesitas berdasarkan persepsi citra tubuh, pengaruh teman sebaya, dan faktor lainnya pada siswa SMP Negeri 98 Jakarta Selatan tahun 2017 = The difference of proportion in the prevalence of obesity prevention behaviors based on perception of body image, effect of peer group, and other factors among students of 98 Junior High School Jakarta Selatan 2017