Sistem Inferensi Fuzzy Untuk Penentuan Status Gizi Menggunakan Pendekatan Indeksmassa Tubuh (Imt)

Nutritional status is an important indicator in assessing public health. The conventional method of determining nutritional status based on Body Mass Index (BMI) is crisp, making it less able to represent ambiguous conditions around category boundaries. This study applies a Mamdani Fuzzy Inference System (FIS) to determine nutritional status based on BMI, using population data from a sub-district (kelurahan) in the city of Medan as a case study. The research stages include BMI calculation, fuzzification, inference using a rule base, and defuzzification using the centroid method. Testing on 20 sample data points shows that the fuzzy system produces results consistent with the conventional method in 75% of cases, while the remaining 25% occur in borderline BMI values where the fuzzy system provides a more nuanced classification than the rigid conventional threshold. These findings indicate that the fuzzy approach offers a smoother and more representative classification of nutritional status, and can serve as a decision-support tool for community health workers (kader posyandu) and healthcare practitioners. Keyword: Fuzzy Logic, Mamdani, Nutritional Status, Body Mass Index, Decision Support System. Abstrak: Status gizi merupakan indikator penting dalam menilai derajat kesehatan masyarakat. Metode konvensional penentuan status gizi berdasarkan Indeks Massa Tubuh (IMT) bersifat tegas (crisp) sehingga kurang mampu merepresentasikan kondisi ambigu di sekitar batas kategori. Penelitian ini menerapkan Fuzzy Inference System (FIS) metode Mamdani untuk menentukan status gizi berdasarkan IMT, dengan studi kasus data masyarakat di salah satu kelurahan di Kota Medan. Tahapan penelitian meliputi perhitungan IMT, fuzzifikasi, inferensi menggunakan rule base, dan defuzzifikasi dengan metode centroid. Hasil penelitian menunjukkan bahwa sistem fuzzy mampu memberikan klasifikasi status gizi yang lebih halus dan representatif dibandingkan metode ambang batas konvensional, sehingga dapat menjadi alat bantu pendukung keputusan bagi kader posyandu maupun tenaga kesehatan. Kata kunci: Logika Fuzzy, Mamdani, Status Gizi, Indeks Massa Tubuh, Sistem Pendukung Keputusan.