{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T16:12:48Z","timestamp":1790784768639,"version":"4.1.0"},"reference-count":39,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T00:00:00Z","timestamp":1775606400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Soonchunhyang University Research Fund"},{"id":[{"id":"https:\/\/ror.org\/03qjsrb10","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Patient-Centered Clinical Research Coordinating Center","award":["RS-2025-02304185"],"award-info":[{"award-number":["RS-2025-02304185"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Background\/Objectives: Body mass index (BMI) cannot distinguish fat mass (FM) from fat-free mass (FFM). The fat-free mass index (FFMI = FFM\/height2) and fat mass index (FMI = FM\/height2) decompose BMI into lean and fat components. We aimed to establish the first nationally representative, BIA-based FFMI and FMI reference values for Korean adults, visualize body composition trajectories, and classify obesity subtypes using the body composition chart. Methods: Cross-sectional data from 10,140 participants (4508 men, 5632 women; aged 10\u201380 years) from KNHANES IX (2022\u20132023) were analyzed. Multifrequency BIA (InBody 970) measured FFM and FM. Obesity subtypes (%BF \u2265 25% men, \u226535% women) were classified as underlean (FFMI &lt; P5), proportional (P5\u2013P95), or heavy (&gt;P95) relative to an 18\u201359-year-old reference. Results: In men, FFMI peaked at 19.1 kg\/m2 (30\u201349 years), declining 9.7% by 70\u201380 years, while FMI remained stable. In women, FMI increased 44% with stable FFMI. Underlean obesity in men rose from 0.7% (30\u201339 years) to 17.4% (70\u201380 years), undetected by BMI or waist circumference. Conclusions: These reference values and body composition chart provide practical tools for identifying underlean obesity and assessing body composition beyond BMI in Korean adults.<\/jats:p>","DOI":"10.3390\/nu18081170","type":"journal-article","created":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T09:49:44Z","timestamp":1775641784000},"page":"1170","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["National Reference Values of FFMI and FMI Using Body Composition Chart in Korean Adults"],"prefix":"10.3390","volume":"18","author":[{"given":"Hyeoijin","family":"Kim","sequence":"first","affiliation":[{"name":"Department of Physical Education, Korea National University of Education, Chungju 28173, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4676-8483","authenticated-orcid":false,"given":"Yong Hee","family":"Hong","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon 14584, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9489-2104","authenticated-orcid":false,"given":"Young Charles","family":"Jang","sequence":"additional","affiliation":[{"name":"Department of Orthopedics, School of Medicine, Emory Musculoskeletal Institute, Emory University, Atlanta, GA 30329, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3819-2469","authenticated-orcid":false,"given":"Youngil","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of Movement Sciences and Health, Usha Kundu, MD College of Health, University of West Florida, Pensacola, FL 32514, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-0194-8201","authenticated-orcid":false,"given":"Jae Young","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of ICT Convergence, Soonchunhyang University, Asan 31538, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7771-9027","authenticated-orcid":false,"given":"Seon Ho","family":"Eom","sequence":"additional","affiliation":[{"name":"Department of Sports Medicine, Soonchunhyang University, Asan 31538, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sochung","family":"Chung","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Konkuk University Medical Center, School of Medicine, Konkuk University, Seoul 05030, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5933-2785","authenticated-orcid":false,"given":"Chul-Hyun","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of ICT Convergence, Soonchunhyang University, Asan 31538, Republic of Korea"},{"name":"Department of Sports Medicine, Soonchunhyang University, Asan 31538, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1097\/NT.0000000000000092","article-title":"Body mass index: Obesity, BMI, and health: A critical review","volume":"50","author":"Nuttall","year":"2015","journal-title":"Nutr. 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