Underweight merupakan masalah gizi yang umumnya dialami oleh anak-anak berusia di bawah 5 tahun, yang dapat menimbulkan dampak negatif seperti penurunan daya tahan tubuh, penurunan fungsi kelenjar pituitary, tiroid, gonad, gangguan psikologis serta menimbulkan masalah gizi lain yaitu wasting atau stunting (Ali, 2006; Mamhidira, 2006; WHO, 2010; Andriani, 2012; Mahan, Raymond, 2017). Jumlah anak berusia 0-59 bulan yang menderita underweight di wilayah Jakarta Pusat pada tahun 2017 tercatat sebanyak 18,1% (Kementerian Kesehatan Republik Indonesia, 2018). Kejadian underweight pada anak dakarena faktor-faktor seperti asupan gizi, penyakit infeksi, praktik IMD, praktik ASI eksklusif, karakteristik keluarga dan lainnya. Untuk mengetahui proporsi underweight, hubungan antara faktor-faktor tersebut serta faktor dominan kejadian underweight maka dilakukan penelitian dengan desain cross-sectional pada anak usia 25-30 bulan di Kecamatan Gambir dan Kecamatan Sawah Besar, Jakarta Pusat. Total sampel penelitian berjumlah 121 anak. Hasil penelitian menunjukkan persentase anak yang memiliki status gizi underweight sebesar 25.6%. Hasil analisis dengan uji chi-square menandakan ada perbedaan signifikan pada asupan energi (P-value = 0.027), asupan karbohidrat (P-value = 0.035), tingkat pendidikan ayah (P-value = 0.045), pendapatan keluarga (P-value = 0.004) terhadap underweight. Hasil analisis regresi logistik ganda menandakan asupan karbohidrat merupakan faktor dominan underweight (OR = 7.7).

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Underweight is a nutritional problem that is generally experienced by children under 5 years of age, which can cause negative effects such as decreased endurance, decreased function of the pituitary gland, thyroid, gonads, psychological disorders and cause other nutritional problems namely wasting or stunting (Ali, 2006; Mamhidira, 2006; WHO, 2010; Andriani, 2012; Mahan, Raymond, 2017). The number of children aged 0-59 months suffering from underweight in the Central Jakarta area in 2017 was 18.1% (Ministry of Health of the Republic of Indonesia, 2018). The incidence of underweight in children can be caused by direct and indirect factors such as nutritional intake, infectious diseases, IMD practices, exclusive breastfeeding practices, family characteristics and others. To determine the proportion of underweight, the relationship between these factors as well as the dominant factors of underweight events, a cross-sectional study was conducted on children aged 25-30 months in Gambir Subdistrict and Sawah Besar Subdistrict, Central Jakarta. The total sample of the study amounted to 121 children. The results showed the percentage of children who had underweight nutritional status was 25.6%. The results of the analysis with the chi-square test showed there were significant differences in energy intake (P-value = 0.027), carbohydrate intake (P-value = 0.035), father's education level (P-value = 0.045), family income (P-value = 0.004) against underweight. The results of the multiple logistic regression analysis showed that carbohydrate intake was a dominant factor underweight (OR = 7,7).