# Body composition (lean mass, fat mass, visceral fat)

Source: https://onco.cc/terms/body-composition/  
OnCo record `body-composition` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

What a person's weight is made of: muscle, fat under the skin, fat around the organs. It predicts cancer outcomes far better than weight or BMI, and can be read from routine CT scans.

## Summary

BMI misclassifies sarcopenic obesity and muscular individuals. CT at L3 gives skeletal muscle area and density, visceral and subcutaneous fat; DXA and bioimpedance are alternatives. Low muscle mass and low muscle density predict toxicity, complications and survival across cancers; high visceral fat predicts recurrence in colorectal cancer independently of BMI. Automated segmentation makes opportunistic reporting practical.

## Fields

- Kind: Term
- Last checked: 2026-09-08
- Also known as: Skeletal muscle index; L3 muscle area; Visceral adiposity

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Body_composition
- Wikipedia: https://en.wikipedia.org/wiki/Body_composition

## Connected records

- ideas: [GLP-1 receptor agonists as adjuvant weight-loss therapy in HR-positive breast cancer](https://onco.cc/ideas/idea-nl-glp1-adjuvant-hr-breast/), [Read muscle loss automatically from scans patients already have](https://onco.cc/ideas/idea-bio2-ai-sarcopenia-from-ct/)
- technologies: [AI in radiology](https://onco.cc/technologies/radiology-ai-screening/), [Cachexia pharmacotherapy: GDF-15 blockade, anamorelin, olanzapine](https://onco.cc/technologies/cachexia-appetite-pharmacotherapy/), [CT (computed tomography)](https://onco.cc/technologies/ct/), [CT body composition and sarcopenia measurement](https://onco.cc/technologies/ct-body-composition-sarcopenia/), [Dietitian-led weight-loss programmes in HR-positive breast cancer](https://onco.cc/technologies/dietitian-led-weight-loss-breast/), [Exercise during chemotherapy and radiotherapy](https://onco.cc/technologies/exercise-during-chemotherapy/), [GLP-1 receptor agonists and obesity-related cancer risk](https://onco.cc/technologies/glp1-agonists-cancer-risk/), [Measuring muscle and fat on scans the patient already had](https://onco.cc/technologies/rejuv-measure-body-composition/), [Muscle and strength after treatment: sarcopenia, cachexia and what rebuilds](https://onco.cc/technologies/muscle-recovery-after-cancer-treatment/), [Oncology nutrition assessment and medical nutrition therapy](https://onco.cc/technologies/nutrition-screening-mnt/), [Resistance training and protein for cachexia and sarcopenia](https://onco.cc/technologies/resistance-training-cachexia/)
- terms: [Cancer cachexia](https://onco.cc/terms/cachexia/), [Obesity-related cancers (IARC list of 13)](https://onco.cc/terms/obesity-related-cancers/), [Sarcopenia](https://onco.cc/terms/sarcopenia/)
- trials: [Ponsegromab phase 2 in cancer cachexia](https://onco.cc/trials/ponsegromab-phase-2/), [ROMANA 1 and ROMANA 2](https://onco.cc/trials/romana-1-2/)
- pathways: [Lipid synthesis, uptake & cholesterol](https://onco.cc/pathways/lipid-metabolism-cancer/)

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JSON: https://onco.cc/api/v1/entities/body-composition.json