What Is Skinny Fat?

Skinny fat is a very popular phrase that is widespread across the internet, especially on social media. As a very young science, at present it is grossly misunderstood.

So, what is skinny fat science, exactly? 

Technically, skinny fat is normal weight obesity (NWO) and scientifically/medically defined (1) as having too much/excess body fat even when within healthy/safe/normal Standard BMI (2, 48, 49, 52), which is 18.5 to 24.99. In 2006, A De Lorenzo (3, 21) is credited with the first (4) known use of the term normal weight obesity. Subsequently, later that same year Dr. Jimmy Bell (5, 51) coined the acronym TOFI — “thin on the outside, fat on the inside” — which has come to commonly be known as skinny fat (AKA skinny fat syndrome).

By roughly 2010, skinny fat started to emerge as a term in health and fitness communities. The first NIH normal weight obesity definition was published in 2016 (1). As of March 2025, skinny fat is not yet formally recognized as a medical diagnosis. 

What Is Skinny Fat – The Six Types

According to the Standard BMI* definition (6, 7, 8, 9, 10, 11, 48, 49, 52), once you are within safe/normal Standard BMI you no longer have any excess white fat/yellow fat (regular fat/adipose tissue) on your body and are not overweight (BMI 25 to 29.99) or obese (BMI 30+). Being skinny fat (NWO) directly contradicts the Standard BMI definition and is technically impossible.

How is it possible to be within safe Standard BMI and still have too much/excess body fat?

Skinny fat is possible because the excess body fat the person is experiencing is not excess regular white/yellow fat, it is one or more of the other 5 types of skinny fat which include:

1) Cellulite (main type),
2) Thin Fat (main type),

3) Loose Skin (typically a result of excess regular white/yellow fat weight loss and making thin fat or cellulite worse),

4) Saggy Skin (typically a result of excess regular white/yellow fat weight loss and making thin fat or cellulite worse), and

5) Crepey Skin (can be made worse by excess regular white/yellow fat weight loss).

As well as:

6) Normal Weight Obesity (normal weight obesity can only exist when someone is within safe/healthy “normal weight” Standard BMI of 18.5 to 24.99 and can involve any of the other 5 types of skinny fat, particularly thin fat and cellulite).

Skinny fat is different than regular obesity which is defined as having too much regular white/yellow body fat (7, 8, 9, 10, 11) on your body, taking you outside safe BMI. Metabolically healthy obesity/MHO (12, 13) is defined as having normal vitals and, all things considered, being healthy yet experiencing BMI obesity. Whereas thin fat, cellulite, loose skin, saggy skin, and crepey skin can exist at any BMI, while normal weight obesity can only exist within safe/normal BMI. 

Is Skinny Fat Unique Tissue?

Muscle is unique tissue. Regular white/yellow fat is unique tissue. 

Cellulite is unique fibrous tissue (14, 15). More than 80%+ of women (15, 16) and less than 10% of men (16) globally have cellulite, yet 0% have ever gotten rid of it. At this time, there is no FDA-approved way to permanently (15, 16) get rid of cellulite or any other type of skinny fat. You can only reduce it. 

Although the science of skinny fat is young and we are not sure what kind of tissue thin fat (20, 21, 22, 23) is, the very latest science indicates that “…skinny fat cells…differ from regular fat cells…”. We are certain that thin fat tissue is not muscle tissue or regular fat tissue. This is why 100% of eating disorder people (anorexia, bulimia, BED, etc.) fail to starve away skinny fat – you can technically lose 100% of your regular fat yet your skinny fat will remain.

Can thin fat tissue turn into cellulite tissue or vice versa? We don’t know without more scientific research. But we do know that skinny fat tissue and regular fat tissue are NOT the same tissue, they are different. Visceral fat (24, 25) is only regular fat (or brown or beige fat). Skinny fat tissue — thin fat and cellulite — is unique tissue and is ONLY subcutaneous (26). 

Poland Syndrome and Hypotonia

Other similar known genetic muscle disorders include Poland Syndrome (53, 54) — a lack of muscle tissue and other tissues and bone — as well as hypotonia(27), or a lack of muscle tone. 

Skinny Fat Science Is Very Young and Evolving

According to Google, skinny fat is too much visceral and belly fat (subcutaneous) – which is too much regular white/yellow body fat –  even when within safe BMI (which absolutely contradicts and violates the Standard BMI definition) while having low muscle mass and is caused by poor diet and exercise. There is zero science to back up this causal claim (post appropriate comments with links to legitimate scientific studies that prove otherwise).

Please explain (comment section below) how this BMI 22.7 professional trainer (28) who is experiencing skinny fat tissue (thin fat) on their love handles and lower back is experiencing excess visceral and belly fat as well as too much regular body fat and low muscle mass, and how poor diet and exercise caused it:

Research Participant 1170

This 23-year-old research participant (29) has a safe Standard BMI of 24.6 (three left images) with obvious skinny fat including thin fat, cellulite, and normal weight obesity. The right three pictures are after further safe weight loss and reaching a safe Standard BMI of 21.3, yet the skinny fat remains.

According to mainstream science/medicine, once you are within safe Standard BMI you are the Standard Body Type One (BT1) found in any scientifically approved human body anatomy book/resource (18, 19, 17) with all 600+ muscles developed. However, research participant 1170 is well within safe BMI while having indisputable skinny fat tissue where they should have default genetic muscle/mass. They are not a Standard BT1, just like the BMI 22.7 pro trainer. 

What Causes Skinny Fat?

The typical spiel on social media and online, in general — including most medical professionals — is that poor diet (too many carbs, too little protein), exercise (too much cardio, too little resistance), and lifestyle cause loss of muscle tissue and that lost muscle tissue becomes skinny fat. But, it is an undisputed scientific/medical fact that this is not how human tissue works (30, 31).

Muscle tissue cannot become any kind of fat tissue, be it regular fat, brown fat, beige fat, or skinny fat. No amount of diet/protein, exercise, or lifestyle magically turns skinny fat tissue into muscle tissue or gets rid of, prevents, or avoids skinny fat, or the like. This is not how human tissue works!

Examples of Fully Developed Genetic Default Muscle Tissue Versus Not

For example, here is Christian Bale (32), genetically blessed with a Standard Body Type One and all 600+ muscles fully developed from birth (33), after extreme weight loss for a movie role including obvious lost muscle tissue:

According to basically everyone everywhere, including medical professionals, Christian Bale should be experiencing skinny fat. But there is no sign of any type of skinny fat tissue on his body, even when he is emaciated. The muscle definition is crystal clear, even with significant loss of muscle mass.

Skinny fat is real genetic tissue (thin fat, cellulite) and is influenced by diet, exercise, and lifestyle. 

Moreover, many NFL linemen are experiencing skinny fat tissue. These are top elite players — significantly less than 1%, roughly 1700 (34, 35) total players out of the entire population make the league, let alone achieve NFL starting player status — who are in the best shape of their life, yet they are experiencing skinny fat tissue where genetically they should have default muscle mass.

For instance, see the genetic skinny fat tissue (thin fat) on these two (right, left) elite NFL offensive linemen (36, 37):

And it is likely even elite three-time Super Bowl champion NFL TE Travis Kelce (38) is experiencing skinny fat relative to his love handles and lower back, at least. Genetics. Maybe even Taylor Swift (39).

Genetics and Body Composition

Genetics is the foundation (40, 41, 42, 43, 44) of the human body and determines unique genetic body composition. Diet, exercise, and lifestyle directly influence body composition including skinny fat, but they do not determine body composition. At this time, you cannot naturally, permanently (45) change your unique genetics including skin color, hair color, eye color, height, breast size, genital size, facial features, body composition, etc. You can, indeed, temporarily (epigenetically)(46, 45) change/recomp your body composition with diet, exercise, and lifestyle. And, with enough hard work for your entire life, you may even be able to maintain the changes.

The younger you are, the more motivated you are to recomp/change your body. Then life happens, and motivation wanes for most people and you eventually return to your original default genetic body composition, like Research Participant 378 (47). Which is the current nature of human genetics. The younger you are, the harder it can be to discern skinny fat (which is only subcutaneous); especially thin fat. Body dysmorphia and skinny fat go hand-in-hand.

How To Fix Skinny Fat

*It is important to note that the Standard BMI (Body Mass Index) is the current standard — its’ first known mention in the medical literature was in July 1972 (48), it became the international standard (World Health Organization/WHO) in the early 1980s (48), and in June 1998 the U.S.A National Institute of Health approved the current BMI as the standard (49, 48) — but it is not particularly accurate. The Standard BMI fails to effectively account for genetics, excess muscle/mass (genetic or added via exercise), any type of skinny fat, race, gender, or age, no less, and is best used as a guideline. The Body Type Science Theory research (50) is working on making the Standard BMI, Standard BMR (basal metabolic rate), and Standard Body Type One (BT1) more accurate. 

References

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