Why You Should Care About Building Muscle

Good morning!

Somewhere along the way, muscle became a vanity metric. It became something you worried about if you lived at the gym, followed fitness influencers, or had a pair of shorts that needed to look particularly impressive. For everyone else, muscle was mostly an afterthought, something you noticed when you caught yourself in a mirror and thought, Huh, when did my arms get like that?

But muscle is doing far more than filling out a T-shirt. It's one of the most metabolically active tissues in your body, helping regulate blood sugar, support your bones and joints, maintain mobility, and keep you resilient as you age. How much muscle you have, and how well you maintain it, has implications for your health that go far beyond aesthetics.

This week, we're looking at why muscle matters even if you couldn't care less about looking muscular.

Key Takeaways

• Muscle helps regulate blood sugar and communicates with other organs through chemical signals that influence metabolism, brain health, and immune function.

• Muscle loss can begin as early as your 30s and typically accelerates after 50.

• Two to three resistance-training sessions per week, combined with adequate protein, can help build and preserve muscle at any age.

CORE

Muscle is a Metabolic Organ

Most people think of muscles as mechanical… it's what moves your body, lifts things, keeps you upright. And that's true, but it's an incomplete picture of what muscle actually does.

Under normal conditions, skeletal muscle is responsible for the majority of insulin-stimulated whole-body glucose disposal, meaning that after you eat, it's primarily your muscle tissue that pulls glucose out of the bloodstream and puts it to use.

This single fact changes the framing of why muscle matters. It means that having more muscle isn't just about strength, it's also about metabolic capacity. A larger muscle mass provides a larger glucose disposal depot, which blunts post-meal blood sugar spikes, reduces the insulin demand placed on the pancreas, and over time lowers the risk of insulin resistance and type 2 diabetes.

Losing muscle means losing some of that metabolic capacity. Aging, prolonged inactivity, and inadequate protein intake can all contribute to muscle loss, and with less muscle available to handle glucose, maintaining healthy blood sugar becomes more difficult.

The Chemical Messages Muscle Sends

Here's the part that most people have never heard of, and it's really surprising.

When muscle contracts during exercise, it also secretes a class of proteins called myokines. These are essentially chemical signals that travel through the bloodstream and communicate with other organs. During exercise, skeletal muscles secrete various molecules that participate in the crosstalk between organs and play an active role in neurological, metabolic, cardiovascular, and immune processes.

Take irisin, for example. Exercise stimulates its release, and it can reach the brain, where it promotes BDNF, a protein involved in maintaining and supporting neurons and associated with cognitive function and mood. IL-6 is another myokine that behaves differently depending on where it comes from: when released by contracting muscle during exercise, it can help regulate inflammation and improve insulin sensitivity. IGF-1, meanwhile, is involved in muscle growth and maintenance, bone health, and processes that support the nervous system.

Together, these signals help translate the physical act of moving your muscles into changes throughout the body, influencing glucose regulation, fat metabolism, energy production, immune function, and more.

When (and why) We Lose Muscle

Muscle loss isn't something that happens suddenly. It's a slow, continuous process that begins earlier than almost anyone expects and accelerates quietly over time.

Muscle mass starts declining naturally at roughly 0.5-1% per year beginning in your 30s. That rate accelerates after 50, and by the time most people notice something has changed (less strength, slower recovery, difficulty with things that used to be easy) the loss has been accumulating for years. A quick disclaimer, this is not a diagnosis, rather a natural part of aging.

What Actually Builds and Preserves Muscle

Resistance training is the main driver. This type of training means making your muscles work against resistance, usually weights, machines, resistance bands, or even your own body weight. Unlike cardio, which primarily trains your heart and endurance, resistance training gives your muscles a direct stimulus to grow stronger and maintain muscle mass. Research consistently supports two to three resistance-training sessions per week, with exercises that work the major muscle groups as an effective approach for maintaining and building muscle.

Protein is the raw material. Your muscles are constantly breaking down and rebuilding, and adequate protein supplies the amino acids needed to maintain that process. It's also useful to spread protein throughout the day rather than eating most of it in one enormous dinner, because muscle protein synthesis has a limit to how much it can respond to in a single meal. Current research suggests roughly 0.7-1 gram of protein per pound of body weight per day for active adults, with around 25-40 grams per meal providing a useful target for stimulating muscle protein synthesis.

Muscle building doesn't stop with age. This is worth saying plainly because it's the most common misconception in this area. Even elderly adults who begin resistance training for the first time experience meaningful improvements in strength, balance, and independence. Age slows the rate of adaptation, but the capacity to adapt never disappears. Starting later produces smaller absolute gains than starting earlier, but the protective effects of building and maintaining muscle are available at any age.

ENDNOTE

Final Thoughts

The case for muscle, then, isn't about aesthetics. It's about maintaining a body that can manage blood sugar, respond to physical demands, support your bones and joints, and keep doing the things you want it to do as you get older. That's a pretty good reason to care about what's happening underneath the T-shirt.

Until next week!

Adrian Macdonald | Team Dietitian | The 8% Newsletter Author