{
  "abstract": "BackgroundThinness-oriented body ideals are well described among young Japanese women, but variation in visual and numerical ideals by sex, age, and current BMI remains unclear.\n\nMethodsWe analysed an unweighted web-panel sample of 27,359 Japanese adolescents and adults aged 15-69 years from the Survey of Body Shape and Health Awareness in Japanese People, a cross-sectional web-based survey. Current and ideal BMI were derived from self-reported height and weight, and visual orientation from ideal versus perceived current silhouette. Adult BMI-stratified analyses included participants aged 20-69 years.\n\nFindingsAmong 27,359 participants (10,094 men and 17,265 women), relative thinness-oriented indicators increased with current BMI in both sexes. Among normal-weight women, 74{middle dot}7-83{middle dot}7% selected a smaller ideal silhouette and 79{middle dot}2-91{middle dot}2% reported an ideal BMI lower than current BMI. These indicators were also present among underweight women aged 20-29 years (44{middle dot}9% and 43{middle dot}4%, respectively), but declined with age. Most underweight men reported weight-gain-oriented ideals. Fine stratification showed that thinness-oriented ideals among women were common in low-normal and mid-normal BMI strata.\n\nInterpretationBody-size ideals differed by sex, age, and current BMI. Thinness-oriented ideals among women extended beyond obesity and young adulthood, whereas underweight men generally preferred a larger body. Longitudinal and behavioural studies are needed.\n\nFundingCabinet Office of Japan Strategic Innovation Promotion Program (SIP), \"Inclusive Community Platform\" (grant no. SIPCP23C02).\n\nResearch in contextO_ST_ABSEvidence before this studyC_ST_ABSWe searched Web of Science from database inception to May 11, 2026, when the search was updated for submission, using combinations of the terms \"body image\", \"body dissatisfaction\", \"thinness\", \"underweight\", \"age\", and \"sex\". We primarily considered articles published in English or Japanese. We did not restrict eligibility by study design or participant age or sex, but excluded studies conducted exclusively in patients with eating disorders, anorexia nervosa, or other psychiatric disorders. Previous studies from Japan mainly focused on adolescent girls and young women, whereas evidence covering men, middle-aged and older adults, and detailed current-BMI strata was limited. Most of the available evidence was cross-sectional, and heterogeneity in study populations, sampling methods, and measures of body image limited direct comparisons across studies.\n\nAdded value of this studyThis large web-based survey maps visual and numerical body-size ideals simultaneously by sex, age, and current BMI in Japan. Fine BMI stratification shows that thinness-oriented ideals among women are already common in low-normal and mid-normal BMI strata, and the analysis highlights contrasting ideals among underweight women and men.\n\nImplications of all the available evidenceBody-image-sensitive public-health research should extend beyond young women and should consider sex, age, and current BMI jointly. Longitudinal and intervention studies are needed to determine whether these ideals influence weight-control behaviour, nutritional status, body composition, or movement into and out of underweight.",
  "abstract_shown": true,
  "affiliations": [
    "Juntendo University"
  ],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 7,
  "authors": [
    {
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        0
      ],
      "name": "H. Tabata"
    },
    {
      "name": "S. Sakamoto"
    },
    {
      "name": "K. Fukumura"
    },
    {
      "name": "M. Kanda"
    },
    {
      "name": "Y. Adachi"
    },
    {
      "name": "Y. Yoshizawa"
    },
    {
      "name": "Y. Tamura"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/1rqbz8j7kzjxz.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.19.26365487",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.10.19.26365487v1.full",
  "id": "1rqbz8j7kzjxz",
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  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "medrxiv",
      "epidemiology"
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    [
      "openalex",
      "3203|Eating Disorders and Behaviors"
    ]
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  "openalex": "W7222961477",
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.10.19.26365487v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-19",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/1rqbz8j7kzjxz.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:12Z",
      "native_id": "10.64898/2026.10.19.26365487",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.10.19.26365487v1"
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  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:epidemiology",
      "subfield": "epidemiology-public-health"
    }
  ],
  "title": "Sex-, age-, and BMI-specific patterns of visual and numerical body-size ideals in Japan: a large cross-sectional web-based survey",
  "title_text": "Sex-, age-, and BMI-specific patterns of visual and numerical body-size ideals in Japan: a large cross-sectional web-based survey",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:12Z",
  "url": "https://research.draconitic.com/paper/1rqbz8j7kzjxz",
  "venue": "medRxiv",
  "versions": []
}