Is Muscle/Mass Genetic and How Does It Affect Skinny Fat?

Is muscle/mass genetic? Genetics are the foundation of the human body and muscle/mass tissue is highly heritable (1, 2). Some people are genetically blessed with fully developed muscle/mass, as per the Standard Body Type One (BT1)(3, 4). Others, not so much.

Technically, there are two types of muscle fibers (5, 6, 7, 8, 9); slow twitch (Type I) and fast twitch (Type II, A & B). Type I slow twitch muscle fibers, AKA red fibers because they contain more blood-carrying myoglobin, can provide their own source of energy and sustain basic force for an extended time while being resistant to fatigue. For instance, the muscles responsible for maintaining posture have a higher density of slow-twitch fibers. More aerobically efficient, these fibers are particularly receptive to muscular endurance (toning).

Whereas, Type II fast twitch muscle fibers, AKA white fibers because they do not contain much blood, are defined by two variations. Type IIA fibers are fast oxidative glycolytic, use oxygen to help convert glycogen to ATP, and are relatively resistant to fatigue. Type IIB fibers are fast glycolytic, rely on ATP stored in the muscle cell to generate energy, and fatigue rapidly. Fast-twitch muscle fibers are more suited for strength, power, and explosive performance.

Is Muscle/Mass Genetic and How Does It Affect Skinny Fat?

The total number of default genetic muscle fibers a person has is set at or around birth (10, 11, 12, 13). The rate of muscle growth is by far the greatest in the late stages of pregnancy and in the early postnatal period. At this time, the only reliable ways to accurately know how much genetic default muscle/mass tissue you have are via a Magnetic Resonance Imaging (MRI)(gold standard)(14, 15) scan or computed tomography (CT/CAT)(16, 17) scan, both of which are expensive and uncommon.

The only way to know your Type I and Type II muscle fiber ratio is through an invasive muscle biopsy (18, 9), which is also expensive and uncommon. Although a specific MRI scan may be able to indirectly (55, 56, 57, 61) provide information about muscle fiber composition based on differences in relaxation times, at least, with further theories pending like the myotype (62).

The vast majority of human beings — nearly all — have no idea what their default genetic muscle fiber/tissue/mass measurements are and never have. Their doctors do not know. No one knows. But we do know that many people are born with less muscle. Just as we know genetics play a significant role in how much muscle a person can build (19, 20, 21, 22, 2, 12) — how easy or how hard it is for each person to add muscle mass and maintain it — including the BCL6 gene.

What Happens When a Person is Born with Deficient Genetic Default Muscle/Mass Tissue?

Muscle is a primary insulin-sensitive tissue (63, 64, 65). The less genetic default muscle tissue/more skinny fat a person has, the more it negatively impacts metabolism, particularly glucose uptake, at least. This directly affects insulin, insulin resistance, type-2 diabetes, and being overweight or obese.

The more skinny fat tissue — thin fat, cellulite (66) — a person is experiencing, the more sensitive they are to sugar and starch carbs (67) (especially refined and processed carbs common in fast, junk, and processed foods). The more they consume, the more their blood glucose spikes and the more insulin their body requires to process things. Over time, too much can lead to insulin resistance and eventually type-2 diabetes, being overweight, and obesity, no less. The average daily American diet consists of roughly 60% (68, 69, 70, 71) fast, junk, and processed foods loaded with refined sugar and starch carbs.

All of this makes losing, maintaining, and managing regular white/yellow body fat (common adipose tissue) more difficult, which makes reducing skinny fat harder. Not to mention, the more underdeveloped genetic default muscle tissue you have, the more skinny fat tissue you have and the more it negatively affects (58, 59, 60) no less than strength, power, reaction time, speed, balance, coordination, agility, flexibility, endurance, athleticism in general, self-confidence, mental health, overall health, and day-to-day-living.

Research Participant 1170

Research participant 1170 (23)(RP 1170) started their regular fat weight loss within safe/healthy Standard BMI at 24.6 — meaning by scientific/medical BMI definition (24, 25, 26, 27, 28), they have no excess regular fat. This is literally how doctors discern the difference between healthy weight and being overweight or obese.

A person cannot have too much regular white/yellow fat and be within safe BMI – it is 100% contrary to and violates the BMI definition. Yes, we know the Standard BMI is inaccurate, but it is the current standard (29, 30) and better than no standard at all. More to the point, just because its accuracy is debatable does not mean it can be contradicted and disregarded.

Skinny Fat Tissue Exists Where Genetic Default Muscle/Mass Should Be, But Is Not

RP 1170 is clearly experiencing normal-weight obesity (66). The excess body fat tissue all over their body — which cannot be and is not regular white/yellow fat (adipose tissue) — is skinny fat tissue in the form of thin fat and cellulite (66). They lost even more regular fat weight down to a BMI of 21.3, yet the genetic default muscle/mass (as per the Standard Body Type One) did not magically appear. The skinny fat tissue is still clearly evident in all the same places it was at BMI 24.6.

In fact, they could lose regular white/yellow fat tissue down to a safe minimum BMI of 18.5, and the genetic default muscle/mass that every Standard Body Type One (BT1) has will not magically appear. This person is not a Standard BT1. They are likely a genetic scientific Body Type Three (BT3)(31), which is defined by how much skinny fat tissue they have relative to vertebrae.

Lost Muscle/Mass Tissue Does Not Become Any Kind Of Fat

Many people claim that RP 1170 just lost muscle mass during weight loss. Now they have regular fat tissue where the muscle tissue was, and have ‘become skinny fat’. But what they are claiming is that muscle tissue turned into fat/skinny fat tissue, which is not possible (32, 33, 34). If that were true, that lost muscle becomes skinny fat, then it would apply equally to 100% all human beings.

Here is Christian Bale when he lost a severe amount of weight for a movie role:

He lost obvious muscle mass, yet he has no indications of any skinny fat tissue. Genetics. Even when he is emaciated the muscle definition is crystal clear. Those people making such claims have no explanation.

Nor can they explain this 22.7 BMI person with obvious skinny fat tissue (thin fat) on his lower back and love handles:

Why did only the muscle on his love handles and lower back turn (impossible)(32, 33, 34) into skinny fat? With no explanation for any of that, the same people will shout, “Stop using genetics as an excuse!” while continuing their outrageous claims by further claiming that with enough hard work in terms of diet and exercise, especially protein and weightlifting, you can turn your skinny fat into muscle (impossible)(32, 33, 34). The best news of all is, thanks to epigenetics, the work you do is permanent.

What Does the Science Say?

Alas, none of that is true (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46). Added muscle mass (above and beyond genetic default) due to epigenetic body recomposition (which does temporarily increase muscle fiber size through hypertrophy) changes from exercise and diet, no less, is gradually lost if the exercise that built it ceases consistency and regularity. Epigenetics are not permanent. Muscle cannot turn into fat or vice versa.

Genetics is not an excuse when it comes to no less than default genetic body composition – how much muscle/mass tissue and skinny fat tissue a person has from birth. Genetics is a fact, and our MRI Study (72) will prove it

Although, genetics is, indeed, not an excuse to be unhealthy. The more skinny fat tissue you are experiencing the more diligent you will have to be with healthy, science-based diet, exercise, and lifestyle choices throughout your life to be a healthy weight and remain healthy.

Is Muscle/Mass Genetic – How Does It Affect Skinny Fat?

All that said, with enough hard work you can reduce any skinny fat tissue you have by safely losing regular white/yellow fat weight and adding muscle mass; you may even look like (or close to) the Standard BT1. And with enough hard work consistently and regularly throughout your life, you can maintain those changes. Moreover, maybe, if you are one of the very rare few people who tempt evolution and cause a positive genetic mutation (47, 48, 49, 50) that is permanent, you might pass it on to your next generation progeny.

Yes, muscle/mass (or lack thereof) is genetic while being directly influenced by diet, exercise, and lifestyle. The more skinny fat tissue you have, the more it affects your regular white/yellow fat weight loss and weight gain efforts along with metabolism (51), diet (52), exercise (53), and lifestyle (54). The Scientific Health Quizzes help make sense of all of that, free options are available.

Is Skinny Fat Genetic?

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