Is Normal Weight Obesity (Skinny Fat) the Same as Sarcopenic Obesity?

The other day an anti-science troll on social media adamantly claimed that skinny fat (normal weight obesity) and sarcopenic obesity are the same thing. No matter the overwhelming scientific evidence and facts presented as counter-points, which were fully ignored and void of any such scientific reciprocation. So, what does the latest science say?

Sarcopenic obesity is defined (1, 2, 3, 4, 5, 6) as the combination of regular obesity (a disease) — having too much/excess regular white/yellow fat (body fat/adipose tissue) which equates to a high body fat percentage and being BMI obese (30+) — while also experiencing sarcopenia. Sarcopenia is defined (7, 8, 9, 10, 11, 12) as an age-related musculoskeletal disease in which muscle mass, strength, and performance are compromised by aging, as early as 30 years old but especially after 40 years old, leading to low skeletal muscle mass accompanied by low muscle function.

Skinny Fat – Normal Weight Obesity (NWO)

Whereas being normal weight obese (skinny fat) is defined (13, 14) as being within safe Standard BMI (18.5 to 24.99) and NOT being BMI obese (30+) yet still somehow experiencing too much/excess body fat.

What kind of body fat (15)? Well, once a person is within safe BMI (18.5 to 24.99) by scientific/medical definition they no longer have too much regular white/yellow fat (body fat/adipose tissue)(13, 15). So we know it is not regular fat. Skinny fat is real genetic tissue (thin fat, cellulite)(13).

How Much Genetic Default Muscle/Mass Did I Start With? – Sarcopenic Obesity and Youth

The latest sarcopenic obesity scientific data (16, 17, 18, 19) in terms of children, adolescents, and young adults is lacking. But, logically, how does sarcopenic obesity even apply to anyone under 30 years old? As already mentioned, sarcopenia, by definition (7, 8, 9, 10, 11, 12), is characterized by people 30 years or older who typically lose skeletal muscle tissue due to normal aging processes.

Technically, people 29 years and younger do not experience sarcopenia, they experience muscle atrophy (20, 21, 22, 23, 24, 25). Poor diet, exercise, and lifestyle, including being too sedentary, can cause muscle tissue loss (atrophy). However, muscle tissue does not turn into fat tissue of any kind (26, 27, 28).

More to the point, no study to date has any scientific data — none — that clearly defines each research participant’s/person’s specific genetic default muscle/mass levels from birth, no less. Thus, no one really knows what each person’s genetic default muscle/mass levels were or are, at all, let alone before they became obese. This means any data we do have is inaccurate, at best, and straight guessing and useless, at worst (you might as well flip a coin).

No One, Not Even Your Doctor, Knows Your Exact Genetic Default Muscle/Mass

All of it makes the gross assumption that either lean body mass & body fat percentage (%) calculations are accurate (they are not (29, 30, 31, 32)) or every research participant/person has the same general amount of genetic default muscle/mass, which is unequivocally false (33, 34, 35).

Some people are, indeed, born with all 600+ muscles fully developed like a Standard Body Type One (BT1)(36, 37, 38). Others are not (33, 34, 35). How much genetic default muscle/mass a person has is determined by each individual person’s unique genetics (39, 40, 41). Not to mention epigenetics (40, 41) like any added muscle mass above and beyond genetic default muscle/mass that a person builds via exercises (42) including weightlifting (resistance exercise) along with proper diet (43).

Is Normal Weight Obesity (Skinny Fat) the Same as Sarcopenic Obesity?

No. Sarcopenic obesity, by definition, is being BMI obese (30+) with sarcopenia. Normal weight obesity (skinny fat), by definition, is NOT being BMI obese (30+) but instead is being a healthy weight (BMI 18.5 to 24.99) with too much body fat (in this case, by definition, not regular fat tissue but skinny fat tissue).

Skinny fat (normal weight obesity) and sarcopenic obesity are two very different, separate, unique things. They are 100% not the same.

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References

1. NIH, National Library of Medicine: Sarcopenic obesity – definition, etiology and consequences, November 2008, Sari Stenholm, Tamara B Harris, Taina Rantanen, Marjolein Visser, Stephen B Kritchevsky, and Luigi Ferrucci. https://pmc.ncbi.nlm.nih.gov/articles/PMC2633408/
2. ScienceDirect: Sarcopenic Obesity, 2020, Asian Journal of Surgery. https://www.sciencedirect.com/topics/medicine-and-dentistry/sarcopenic-obesity
3. MedicalNewToday: Causes and treatment for sarcopenic obesity, May 22, 2023, Zawn Villines. https://www.medicalnewstoday.com/articles/sarcopenic-obesity
4. Wikipedia: Sarcopenic obesity. https://en.wikipedia.org/wiki/Sarcopenic_obesity
5. NIH, National Library of Medicine: Definition and Diagnostic Criteria for Sarcopenic Obesity: ESPEN and EASO Consensus Statement, February 23, 2022, Lorenzo M Donini, Luca Busetto, Stephan C Bischoff, Tommy Cederholm, Maria D Ballesteros-Pomar, John A Batsis, Juergen M Bauer, Yves Boirie, Alfonso J Cruz-Jentoft, Dror Dicker, Stefano Frara, Gema Frühbeck, Laurence Genton, Yftach Gepner, Andrea Giustina, Maria Cristina Gonzalez, Ho-Seong Han, Steven B Heymsfield, Takashi Higashiguchi, Alessandro Laviano, Andrea Lenzi, Ibolya Nyulasi, Edda Parrinello, Eleonora Poggiogalle, Carla M Prado, Javier Salvador, Yves Rolland, Ferruccio Santini, Mireille J Serlie, Hanping Shi, Cornel C Sieber, Mario Siervo, Roberto Vettor, Dennis T Villareal, Dorothee Volkert, Jianchun Yu, Mauro Zamboni, and Rocco Barazzoni. https://pmc.ncbi.nlm.nih.gov/articles/PMC9210010/
6. The Conversation: Sarcopenic obesity can rob people of their strength – but even brief bursts of exercise help a lot, August 6, 2024, Justin Keogh and Carla Prado. https://theconversation.com/sarcopenic-obesity-can-rob-people-of-their-strength-but-even-brief-bursts-of-exercise-help-a-lot-234663
7. Cleveland Clinic: Sarcopenia, June 3, 2022. https://my.clevelandclinic.org/health/diseases/23167-sarcopenia
8. NIH, National Library of Medicine: Sarcopenia, July 4, 2023. Andrew D. Ardeljan and Razvan Hurezeanu. https://www.ncbi.nlm.nih.gov/books/NBK560813/#:~:text=Sarcopenia%20is%20a%20musculoskeletal%20disease,system%20or%20impair%20physical%20activity.
9. WebMD: Sarcopenia With Aging, July 9, 2024, Mary Anne Dunkin and Kim Painter (Medically reviewed by Zilpah Sheikh, MD). https://www.webmd.com/healthy-aging/sarcopenia-with-aging
10. Healthline: How to Fight Sarcopenia (Muscle Loss Due to Aging), May 25, 2017, Matthew Thorpe, MD, PhD. https://www.healthline.com/nutrition/sarcopenia
11. Wikipedia: Sarcopenia. https://en.wikipedia.org/wiki/Sarcopenia
12. Harvard Health Publishing: Preserve your muscle mass, February 19, 2015. https://www.health.harvard.edu/staying-healthy/preserve-your-muscle-mass
13. Skinny Fat Science: What Is Skinny Fat? July 26, 2024. https://skinnyfat.fellowone.com/what-is-skinny-fat/
14. NIH, National Library of Medicine: Normal-weight obesity syndrome: diagnosis, prevalence, and clinical implications, September 2016 (Epub Jul 29, 2016), Lana P Franco, Carla C Morais, Cristiane Cominetti. https://pubmed.ncbi.nlm.nih.gov/27473199/
15. Skinny Fat Science: Are Regular Fat and Skinny Fat the Same Thing?, August 28, 2024. https://skinnyfat.fellowone.com/are-regular-fat-and-skinny-fat-the-same-thing/
16. NIH, National Library of Medicine: Sarcopenic Obesity in Children and Adolescents: A Systematic Review, June 1, 2022, Marcela Zembura and Paweł Matusik. https://pmc.ncbi.nlm.nih.gov/articles/PMC9198401/
17. ScienceDirect: Sarcopenia in youth, July 2023, Volume 144, Han Na Jung, Chang Hee Jung, and You-Cheol Hwang. https://www.sciencedirect.com/science/article/abs/pii/S0026049523001609
18. NIH, National Library of Medicine: Understanding sarcopenic obesity in young adults in clinical practice: a review of three unsolved questions, December 2022, Marwan El Ghoch, Andrea P Rossi, Ludovica Verde, Luigi Barrea, Giovanna Muscogiuri, Silvia Savastano, and Annamaria Colao; Obesity Programs of Nutrition, Education, Research and Assessment (OPERA) Group. https://pubmed.ncbi.nlm.nih.gov/36533664/
19. ScienceDirect: Sarcopenia and poor muscle quality associated with severe obesity in young adults and middle-aged adults, October 2021, Volume 45, Tamyris Lira da Silva, Vanessa dos Santos Chiappetta Salgado Nogueira, and Alessandra Pinheiro Mulder. https://www.sciencedirect.com/science/article/abs/pii/S2405457721002886
20. Cleveland Clinic: Muscle Atrophy, January 21, 2022. https://my.clevelandclinic.org/health/diseases/22310-muscle-atrophy
21. MedlinePlus: Muscle atrophy, December 31, 2023. https://medlineplus.gov/ency/article/003188.htm
22. Wikipedia: Muscle atrophy. https://en.wikipedia.org/wiki/Muscle_atrophy
23. Healthline: What Causes Muscle Wasting?, August 24, 2019, Ann Pietrangelo (Medically reviewed by Elaine K. Luo, M.D.). https://www.healthline.com/health/muscle-atrophy
24. MedicalNewsToday: What to know about muscle atrophy, October 18, 2023, Jamie Eske (Medically reviewed by William Morrison, M.D.) https://www.medicalnewstoday.com/articles/325316
25. ScienceDirect: Muscle Atrophy, 2021, Pharmacological Research. https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/muscle-atrophy 
26. NIH, National Library of Medicine: Muscle-to-fat interaction: a two-way street?, January 1, 2010, Bente K Pedersen. https://pmc.ncbi.nlm.nih.gov/articles/PMC2821541/
27. Healthline: Does Fat Turn into Muscle? What to Know, March 2, 2021, Katey Davidson, MScFN, RD, CPT (Medically reviewed by Jake Tipane, CPT). https://www.healthline.com/nutrition/does-fat-turn-into-muscle
28. The New York Times: The Claim: Muscle Turns to Fat When You Stop Working Out, July 26, 2006, Anahad O’Connor. https://www.nytimes.com/2005/07/26/health/nutrition/the-claim-muscle-turns-to-fat-when-you-stop-working-out.html
29.  Men’s Health: Why You Should Be Wary of Body Fat Tests, February 18, 2019, Christian Finn. https://www.menshealth.com/fitness/a26382163/body-fat-tests/
30. NIH, National Library of Medicine: Utility of Lean Body Mass Equations and Body Mass Index for Predicting Outcomes in Critically Ill Adults with Sepsis: A Retrospective Study, January 26, 2024, Rumiko Shimizu, Nobuto Nakanishi, Manabu Ishihara, Jun Oto, and Joji Kotani. https://pmc.ncbi.nlm.nih.gov/articles/PMC10887861/
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33. Fellow One Research: Body Type Science Research Data. https://www.fellowone.com/category/fellow-one-research/the-four-body-types/body-type-science/body-type-quiz/research-data/
34. LiveScience: Why is it harder for some people to build muscle than others?, July 17, 2023, Kamal Nahas. https://www.livescience.com/health/exercise/why-is-it-harder-for-some-people-to-build-muscle-than-others
35. The New York Times: Why Some People Won’t Be Fit Despite Exercise, February 12, 2022, Gian Kolata. https://www.nytimes.com/2002/02/12/health/why-some-people-won-t-be-fit-despite-exercise.html
36. Britannica: human muscle system, Shane W. Cummings and Robin Huw Crompton (Fact-checked by the Editors of Encyclopaedia Britannica. https://www.britannica.com/science/human-muscle-system
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38. Wikipedia: Muscular system. https://en.wikipedia.org/wiki/Muscular_system
39. NIH, National Library of Medicine: Genetic aspects of skeletal muscle strength and mass with relevance to sarcopenia, April 4, 2012, Stephen M Roth. https://pmc.ncbi.nlm.nih.gov/articles/PMC4816288/
40. Skinny Fat Science: How To Fix Skinny Fat, July 27, 2024. https://skinnyfat.fellowone.com/how-to-fix-skinny-fat/
41. Skinny Fat Science: Can I Have A Skinny Fat Body And Be Fit & Healthy?, October 30, 2024. https://skinnyfat.fellowone.com/can-i-have-a-skinny-fat-body-and-be-fit-and-healthy/
42. Skinny Fat Science: The Best Skinny Fat Exercise, According to Science, August 2, 2024. https://skinnyfat.fellowone.com/the-best-skinny-fat-exercise-according-to-science/
43. Skinny Fat Science: The Best Skinny Fat Diet, According to Science, July 29, 2024. https://skinnyfat.fellowone.com/the-best-skinny-fat-diet-according-to-science/