Shifting your attention from fat to muscle tissue can be really empowering. Gabrielle Lyon likes to say “we’re not overweight, we’re undermuscled”. So today we’re going to dive deep into the importance of muscle and why we need it from a physiological standpoint. To start with the basics, there are a few key types of muscle in your body: smooth muscle (like in your uterus), cardiac muscle, and skeletal muscle. For now, we’re going to focus on skeletal muscle in particular.

The Basics of Skeletal Muscle

Skeletal muscle is a type of striated muscle tissue that is attached to your bones by tendons and is responsible for voluntary movements of your body. These muscles are composed of long, cylindrical cells called muscle fibers, which are multinucleated and contain specialized structures called myofibrils. Myofibrils are made up of overlapping filaments of proteins called actin and myosin, which are responsible for your muscle contractions. 

Every time your skeletal muscle fibers contract, they release myokines. These are a group of cytokines and other peptides with extremely diverse functions, acting locally within your muscle tissue as well as systemically. Myokines play a role in regulating muscle metabolism, inflammation, energy expenditure, and communication between your different tissues and organs. Some well-known myokines are:

• Interleukin-6 (IL-6) – has both pro-inflammatory and anti-inflammatory effects. It is released in response to exercise and can modulate glucose metabolism and lipid oxidation.
• Irisin – released during exercise and is involved in the browning of white adipose tissue, which increases energy expenditure and may have implications for metabolic health and obesity.
• Brain-derived neurotrophic factor (BDNF) – primarily known for its role in the nervous system but it is also produced by skeletal muscle and has been implicated in exercise-induced neuroplasticity and cognitive function.
• Myostatin – negative regulator of muscle growth and is primarily produced in skeletal muscle. Inhibiting myostatin activity can lead to muscle hypertrophy and increased muscle mass.
• Fibroblast growth factor 21 (FGF21) – a metabolic regulator that is secreted by skeletal muscle during exercise and can modulate glucose and lipid metabolism.

Most of us spend a lot of time thinking about our weight, but we’re not thinking about what’s actually going on under the surface of our skin. Typically, the more weight you have to carry around, the more you stimulate your muscles. To understand this concept a bit better, visualize a marbled steak. Just because you have muscle doesn’t mean that it’s always healthy muscle tissue. In the case of the steak, there’s muscle with quite a bit of fat swirled throughout it. This is why it’s often better to mitigate weight gain and really focus on the quality of your muscle tissue.

The Functions of Skeletal Muscle:

• Movement – This one goes without saying but skeletal muscles work in pairs or groups to move your bones around your joints which enables basic activities like walking, running, lifting, and picking things up.
• Glucose Regulation – Through glucose uptake and storage, your skeletal muscles are able to regulate your blood sugar. They do this by taking up excess glucose from your bloodstream, facilitated by insulin, and using it either for immediate energy production during muscle contraction or for storage in your muscle cells (as glycogen). When you’re doing physically demanding activities, this glycogen can be broken down into glucose and used for fuel. Conversely, when your blood sugar levels are low, your skeletal muscles can release stored glucose into your bloodstream to maintain adequate levels for other tissues and organs
• Posture and Stability – Skeletal muscles play a crucial role in maintaining posture and providing stability to your body. They’re continuously working to support your skeleton and keep your body in an upright position against the force of gravity.
• Heat Production – Skeletal muscle generates heat as a byproduct of its metabolic activity, especially during contraction. This process, known as thermogenesis, helps regulate your body temperature and is essential for maintaining homeostasis in your body.
• Protection of Organs – Skeletal muscles, particularly those located in your abdominal and pelvic regions, help protect your vital internal organs. For example, your abs protect your abdominal organs, while your pelvic floor muscles support your pelvic organs.
• Metabolism – Skeletal muscles are highly metabolically active tissues that play a significant role in energy metabolism. They store glycogen, a form of glucose that serves as a readily available energy source during muscle contraction. Additionally, your skeletal muscle mass contributes to your overall metabolic rate, with larger muscle mass associated with higher energy expenditure even at rest. This is why just having more skeletal muscle on your frame actually helps you to lose weight!
• Blood Circulation – Skeletal muscles assist in venous return, which is the process of returning deoxygenated blood back to your heart. Contraction of your skeletal muscles, especially in your legs, helps squeeze blood through your veins and propel it toward your heart, facilitating efficient circulation.
• Respiration – Skeletal muscles, including your diaphragm and intercostal muscles between your ribs, are involved in your breathing. Essentially, your diaphragm contracts and flattens during inhalation, increasing the volume of your thoracic cavity and drawing air into your lungs.
• Fatty Acid Oxidation (aka Beta Oxidation) – The process of breaking down fatty acids to produce energy occurs within your mitochondria which are the energy-producing organelles in your muscle cells. This is important because your skeletal muscles can utilize these fatty acids as a fuel source for ATP production during periods of increased energy demand. Regular physical activity and endurance training can actually enhance your skeletal muscle’s ability to oxidize fatty acids by increasing the number and efficiency of mitochondria and the activity of enzymes involved in fatty acid metabolism.

Why Is There a Big Plant-Based Push Right Now?

During World War II there was significant food rationing. This meant that the most nutrient dense foods, like meat, butter and eggs, were shipped overseas to feed the deployed soldiers – amounting to about one pound of meat per soldier per day. Meanwhile, civilians were encouraged to grow victory gardens and eat more vegetarian-leaning diets. So major food corporations, like Kellogg, had to get creative about how to feed the general population, ultimately landing on carbohydrate dominant, processed, packaged food. What we’re currently experiencing is almost a self-imposed rationing with the same outcome but wrapped in different messaging (largely environmentally based). 

Is Red Meat Bad for You?

The health impact of red meat consumption is a topic of ongoing debate and research within the scientific community. Many of the claims come from the idea that red meat is chock full of saturated fat, which isn’t always the case. Certain cuts of red meat are definitely high in saturated fat (ribeye, T bone) while others are quite lean (tenderloin, top sirloin) so it really comes down to what you’re eating and how often. Some reasons why red meat can be really supportive to our diets are:

• Nutrient Density – Red meat is rich in many essential nutrients, including high-quality protein, iron, zinc, carnitine, zinc, selenium, calcium, serine, creatine and vitamins (especially B6 and B12). All of these nutrients play crucial roles in physiological functions such as muscle building, oxygen transport, immune function, and energy metabolism. Also, red meat contains nutrients that work synergistically. For instance, vitamin B12 and iron work together in the production of red blood cells and energy metabolism.
• Iron Absorption – The heme iron found in red meat is more easily absorbed by the body compared to the non-heme iron found in plant foods. Iron is essential for the production of hemoglobin, which carries oxygen in the blood, and myoglobin, which stores oxygen in muscles.
• Complete Protein: Red meat is a source of complete protein, meaning it provides all 9 essential amino acids that the body needs for protein synthesis and various metabolic processes. It’s certainly possible to get all of these from plants; it just takes more intentionality and planning!
• Satiety: Protein-rich foods like red meat can make you feel fuller for longer, which may aid in weight management by reducing overall calorie intake.
• Creatine: Red meat is one of the richest dietary sources of creatine, a compound made from 3 amino acids that plays a key role in energy metabolism, particularly during short bursts of high-intensity physical activity. Creatine supplementation has been shown to improve exercise performance in certain contexts.

It’s important to point out that we’ve reduced our red meat consumption by around 40% yet heart disease, obesity and diabetes have all gone up. So there’s certainly more to the story here than just red meat being the culprit!

2 Simple Takeaways to Build More Skeletal Muscle 

1. Train hard. It’s not always all about nutrition! Really embrace the mindset of pushing yourself in your workouts and remember that mental strength often follows physical strength so it will get easier. Gabrielle Lyon always says that you’ll never regret being as physically fit as you possibly can be. Resistance training is by far the best way to build skeletal muscle but do whatever form of strength training feels best in your own body. 
2. Prioritize dietary protein. How much? It may seem like a lot, but shoot for one gram of protein per pound of body weight. And if you are occupying a larger body, use the weight that you would be in your ideal scenario. 

To learn more about the importance of muscle and protein you can listen to my conversation with Dr. Gabrielle Lyon on the Quiet the Diet podcast. She goes deep into her own story, from being vegan to eventually building up to 40% muscle with a high protein diet. It’s a good one!

Want more support in eating healthier and losing weight?

By working with one of our Registered Dietitian Nutritionists at Michelle Shapiro Nutrition LLC, you will receive personalized recommendations and one-on-one nutritional counseling to help you reach attainable goals in a way that fits your lifestyle.