Is Skinny Fat Genetic? From the MRI Lab to Your Body: The Evidence

First mentioned in the official literature in 2006 (1), the science of skinny fat remains limited. Because data, evidence, and facts are so scarce, misinformation, disinformation, and confusion are widespread, particularly on social media. Is skinny fat genetic? The scientific evidence is growing.

Do a Google search for “what is skinny fat” and it will reveal results that claim that skinny fat means having too much regular white/yellow body fat within a safe BMI of 18.5 to 24.9. With a secondary mention of low muscle tissue. Ask AI the same thing, and it will most likely regurgitate the same spiel. Inquire further about low muscle, and the common answer states that muscle tissue is lost due to poor diet, exercise, and lifestyle, which leads to excess regular fat even when within safe BMI. However, when analyzed under real scientific scrutiny, none of that holds water.

From the MRI Lab to Your Body: Is Skinny Fat Genetic? The Evidence

The Standard BMI has not been officially updated since 1998 (1). It has not been changed since the first official skinny fat definition was released by the NIH in 2016 (1). There is no doubt the BMI is inaccurate and debatable in terms of effectiveness, but it is the current approved standard and better than no standard at all (anarchy). The Standard BMI definition clearly states that once within safe BMI — 18.5 to 24.99 — a person no longer has any excess regular white/yellow body fat. The initial 2016 NIH skinny fat definition did not change this fact.

Just because the NIH releases a new definition does not mean it automatically, magically changes the existing Standard BMI definition. Nor does it allow medical doctors, social media influencers, or anyone to arbitrarily change the existing Standard BMI definition as they see fit. The initial 2016 NIH skinny fat definition directly contradicts the accepted and approved Standard BMI definition. It is impossible to be within safe BMI and have too much regular white/yellow fat, and this fact will not change until the Standard BMI is officially changed through legitimate, accepted protocol.

Moreover, it is a scientific fact (2, 3, 1) that muscle tissue cannot turn into any kind of fat tissue, or vice versa. There is no debate or doubt about this universally accepted scientific/medical fact. None. Poor diet, exercise, and lifestyle can, indeed, cause muscle tissue loss. But lost muscle tissue does not magically turn into regular white/yellow fat. The claim that skinny fat is merely regular white/yellow fat that is caused when muscle tissue is lost is not supported by any scientific data, evidence, or facts. There is no scientific explanation as to how this would happen (please comment below otherwise).

Skinny Fat is a Lack of Genetic Muscle Tissue

After gathering and analyzing the body composition data, no less, of nearly 500 research participants (5), the common theme that emerges reveals that those who are lacking genetic muscle tissue have some degree of skinny fat (1), and have since birth. No matter how much regular white/yellow fat they lose, the skinny fat does not go away. Likewise, no matter how hard they work at their diet, exercise, and lifestyle, they cannot permanently fix (2) their skinny fat.

They can only reduce it by adding muscle mass anywhere they are experiencing skinny fat. Furthermore, if/when they stop maintaining the added muscle mass, they will gradually lose it (5), eventually returning to their original genetic body composition, including any skinny fat. Just as losing muscle tissue due to poor diet, exercise, and lifestyle can make any existing skinny fat worse. Skinny fat is a lack of genetic muscle (6). Our MRI Study (7) is working on proving things once and for all.

We have developed the Scientific Health Quizzes to accurately determine body composition, especially skinny fat, as well as metabolism and healthy diet, exercise, and lifestyle. Accounts are free, private, secure, and anonymous. Free options are available.

References

1. Skinny Fat Science: What Is Skinny Fat?, July 26, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/what-is-skinny-fat/
2. Skinny Fat Science: How To Fix Skinny Fat, July 27, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/how-to-fix-skinny-fat/
3. Skinny Fat Science: Are Regular Fat and Skinny Fat the Same Thing?, August 28, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/are-regular-fat-and-skinny-fat-the-same-thing/
4. Fellow One Research: Body Type Science Research Data. https://www.fellowone.com/category/fellow-one-research/the-four-body-types/body-type-science/research-data/
5. Skinny Fat Science: Is Muscle/Mass Genetic and How Does It Affect Skinny Fat?, November 20, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/is-muscle-mass-genetic-and-how-does-it-affect-skinny-fat/
6. Skinny Fat Science: Skinny Fat is a Lack of Genetic Muscle – Beyond Normal-Weight Obesity, August 13, 2025. https://skinnyfat.fellowone.com/skinny-fat-science/skinny-fat-is-a-lack-of-genetic-muscle-beyond-normal-weight-obesity/
7. Skinny Fat Science: Scientific Skinny Fat MRI Study – Proving What Skinny Fat Is, March 26, 2025. https://skinnyfat.fellowone.com/skinny-fat-science/scientific-skinny-fat-mri-study-proving-what-skinny-fat-is/