Intramuscular Fat

Skeletal muscle fibers contain intramuscular fat, commonly called intramuscular triglycerides, intramuscular triacylglycerol, or intramyocellular triacylglycerol [IMTG]. It is kept in lipid droplets near the mitochondria, where it can be used as a source of energy when working out.

Human diseases like type 2 diabetes and insulin resistance have been related to excessive intramuscular fat accumulation. AIDS wasting syndrome may be aggravated by the abnormal accumulation of intramuscular fat associated with HIV-lipodystrophy syndrome.

What is Intramuscular Fat?

The term “intramuscular fat” describes fat deposits that are kept inside and between muscle fibers. Although some of this fat is acceptable and even required for energy storage, too much of it might cause health problems. It is frequently observed in older populations, people with type 2 diabetes, and obese people.

In comparison with visceral fat, which surrounds organs, or subcutaneous fat, which is found beneath the skin, intramuscular fat does not usually cause an apparent increase in weight. As a result, it is a risky yet quiet element influencing general health.

Intramuscular fat builds up in skeletal muscle as people age and become obese. Under these circumstances, muscle quality—a measure of muscular strength per unit size—decreases. How obesity affects this performance decline is unknown. Muscle quality is impacted by modifications to structural features (such as fiber pinnations and connective tissue characteristics).

Both inside (intramyocellular) and outside (extramyocellular) of the muscle fibers, intramuscular fat builds up. Healthy muscle contains around 1.5% of intramyocellular fat, while in obese individuals, this amount can approach 5%. The total intramuscular fat may be higher than these amounts since it also includes extramyocellular components. Furthermore, muscles may remodel by hypertrophy to a bigger size and undergo a switch to faster fiber types in obese individuals. Although it has been shown that obesity lowers joint-specific torque (of lean or total body mass), the effects of intramuscular fat and its distribution on muscle mechanics, as well as the mechanisms that may lead to a decrease in such performance, are unknown.

Additionally, intramuscular fat can rise with age, reaching roughly 11% in the elderly. Sarcopenia, a progressive muscle-wasting condition caused by aging, causes a shift to slower fiber types and decreases in size and strength. It has also been demonstrated that muscle atrophy is accelerated by the decreased levels of physical activity that come with obesity in the elderly. The characteristics of connective tissue, such as tendons and aponeurosis, also alter.

IMAT in Various Contexts:

• Meat Quality (e.g., Beef): In cattle, IMAT, or marbling, is a key factor that affects the meat’s flavor, juiciness, and tenderness. Wagyu and other breeds are known for having a high IMAT content.
• Human Health: IMAT plays a more complicated role in human health and is frequently linked to problems with health.

Factors Affecting Human Intramuscular Fat Accumulation:

• Age: Sarcopenia, or the loss of muscular mass as we age, can be accompanied by an increase in the infiltration of fat into the muscles.
• Obesity: Elevated IMAT is frequently linked to higher total body fat levels.
• Physical Inactivity: Not exercising can cause muscles to store fat and decrease muscle efficiency.
• Diet: It has been shown that eating a lot of ultra-processed meals and bad fats raises IMAT.
• Genetics: A person’s genetic makeup might affect their IMAT and other aspects of fat storage.
• Underlying Conditions: Hormonal abnormalities, metabolic syndrome, and type 2 diabetes are among the conditions that might raise IMAT.

Associated with diseases.

Increased intramuscular fat is the result of multiple circumstances where muscle mass is gradually lost and replaced by connective tissue and fat. People with sarcopenia, hormonal imbalances, metabolic disorders including type 2 diabetes and insulin resistance, chronic muscle diseases, and cardiovascular diseases like heart failure and hypertension, for example, have been observed to benefit from intramuscular therapy.

Like all body fat deposits, muscle fat can build up as a result of an unhealthy lifestyle that includes eating too many calories and, most importantly, not exercising. The body will first store excess energy as subcutaneous fat if it has more than it can use. More and more visceral fat is accumulated after these storage capacities are exhausted, and subsequently, more and more fat is stored in the muscles and organs.

When it comes to intramuscular fat, movement is especially significant. We are aware that a person’s risk of storing fat in their muscles increases with their level of physical activity.

High Intramuscular Fat in Humans and Its Effects on Health

According to current research, more intramuscular fat can increase the chance of developing serious heart disease regardless of overall body weight. This “hidden” fat may cause several problems:

• Increased Insulin Resistance: IMF can make it more difficult for the body to use insulin as it should, increasing the risk of type 2 diabetes and, consequently, heart disease.
• Chronic inflammation is linked to excess muscle fat, which raises the risk of heart attacks and strokes by causing atherosclerosis, the hardening and constriction of blood vessels.
• Reduced Muscular Function and Mobility: Elevated IMF levels can result in a more sedentary lifestyle, which is a significant risk factor for heart disease, by reducing muscular strength and mobility.
• Increased Blood Pressure: Because IMF affects vascular function and makes the heart work harder, it has been connected to increased blood pressure.
• Changed Lipid Metabolism: IMF may harm fat metabolism, resulting in decreased HDL and increased LDL, or bad cholesterol.
• Increased Risk of Knee Osteoarthritis: Research has shown a connection between an increased chance of knee osteoarthritis and higher IMAT in the thigh muscles.

Strategies for Reducing Intramuscular Fat

Fortunately, excessive intramuscular fat can be decreased with lifestyle changes:

Regular Exercise: Aerobic and strength training are both beneficial. Aerobic exercise helps burn body fat generally, while strength training helps increase muscle mass, which can decrease fat storage.

• Strength training: Increasing muscle mass and decreasing fat storage can be achieved by lifting weights or performing bodyweight exercises like push-ups, lunges, and squats.
• Cardio exercises: Swimming, cycling, jogging, and walking all help to burn extra fat and strengthen the heart.
• Exercises for mobility and flexibility: Stretching and yoga help maintain muscle function and prevent stiffness.

The foundation of a heart-healthy diet is a diet high in fruits, vegetables, whole grains, and lean proteins. Limit sugary snacks, processed foods, and bad fats (trans and saturated).

• Consume lean proteins to maintain muscular health, such as fish, poultry, tofu, and lentils.
• Increase your consumption of fiber: Whole grains, fruits, and vegetables all aid in controlling cholesterol and blood sugar.
• Reduce your intake of processed foods: Limit consumption of sugary snacks, trans fats, and refined carbohydrates.
• Stay hydrated: Getting enough water helps in muscle and metabolic processes.

Maintain a Healthy Weight: Losing extra body fat might decrease intramuscular fat. It can help to lose even a small amount of weight, like 5–10%.

Stay active: Stay away from prolonged sitting. Throughout the day, schedule quick walks or standing periods.

Monitor your cholesterol and blood sugar levels. Routine examinations can help spot metabolic problems early on, which can lead to the buildup of IMF. Regular physical examinations can assist in detecting early indicators of diabetes, excessive cholesterol, or insulin resistance, allowing immediate care.

Conclusion

One slight but important risk factor for cardiovascular disorders is intramuscular fat. It may not be as obvious as abdominal fat, but it has a significant effect on heart health. You may lower this hidden fat and safeguard your heart by leading a healthy lifestyle that includes consistent exercise, a balanced diet, and weight control.

FAQs

Reference

• Wikipedia contributors. (2025h, March 29). Intramuscular fat. Wikipedia. https://en.wikipedia.org/wiki/Intramuscular_fat
• Eckert, N. (2024, July 24). Dangers of intramuscular fat tissue are often underestimated. Medscape. https://www.medscape.com/viewarticle/dangers-intramuscular-fat-tissue-are-often-underestimated-2024a1000dl0
• Intramuscular Fat | Solutions to feedback. (n.d.). MLA Corporate. https://solutionstofeedback.mla.com.au/sheep/intramuscular-fat-imf/