Underweight merupakan salah satu masalah kekurangan gizi yang rentan dialami oleh anak-anak. Karakteristik anak, orangtua, dan lingkungan menjadi faktor yang mempengaruhi kejadian underweight pada anak, terutama pada anak usia 24-59 bulan. Penelitian ini bertujuan untuk melihat faktor yang mempengaruhi kejadian underweight pada anak usia 24-59 bulan di Pulau Jawa. Penelitian cross-sectional ini menggunakan data sekunder dari IFLS 2014. Total responden pada penelitian ini sebanyak 1270 anak usia 24-59 bulan yang tinggal di Pulau Jawa. Perhitungan dan klasifikasi nilai z-score BB/U menggunakan aplikasi WHO AnthroPlus, sedangkan aplikasi SPSS digunakan untuk mengolah data. Hasil penelitian ini menunjukkan bahwa terdapat 20,2% anak yang mengalami underweight di Pulau Jawa. Variabel yang berhubungan secara signifikan (p-value <0,05) antara lain BBLR, ISPA, diare, frekuensi makan susu dan olahannya, tingkat pendidikan ayah dan ibu, dan status gizi ayah. Sedangkan variabel jenis kelamin, umur kehamilan, pemberian imunisasi dasar, status anemia, riwayat asi eksklusif, semua frekuensi makan selain susu dan olahannya, status gizi ibu, kebiasaan merokok ayah dan ibu, serta wilayah tempat tinggal tidak berhubungan secara signifikan (p-value >0,05) dengan kejadian underweight. Berdasarkan analisis multivariat, frekuensi makan susu dan olahannya menjadi faktor dominan kejadian underweight pada penelitian ini (OR=1,798).

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Underweight is one form of undernutrition that is often experienced by children. Characteristics of children, parents, and the environment were factors affecting the incidence of underweight in children, especially aged 24-59 months. This study aimed to find out the dominant factors affecting underweight in children aged 24-59 months in Java Island. This cross-sectional study used secondary data from IFLS V (2014). Total respondents of this study were 1,270 children aged 24-59 months who lived in Java Island. Z-scores for weight-for-age was determined and classified using WHO AnthroPlus software, while SPSS software was used to process the data. This study found that 20.2% children in Java were underweight. Variables that significantly associated (p-value <0.05) with underweight were LBW, ARI, diarrhea, frequency of eating milk and its products, education level of father and mother, and underweight father. While gender, gestational age, basic immunization, anemia status, exclusive breastfeeding history, other eating frequencies, maternal nutritional status, smoking habits of fathers and mothers, and area of residence were not significantly associated with underweight (p-value >0.05). Based on multivariate analysis, low frequency of eating milk and dairy product was the dominant factor in this study (OR=1.798).