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For years, health advice has pushed us to eat less, weigh less, and take up less space. But according to physician Gabrielle Lyon, D.O., that mindset is undermining our long-term health. On a recent episode of the mindbodygreen podcast, Lyon makes the case that skeletal muscle (not body weight) is one of the most important drivers of longevity, metabolic health, and independence as we age.
Lyon is a fellowship-trained physician, New York Times bestselling author, and the founder of muscle-centric medicine. In her book The Forever Strong Playbook, she challenges the idea that health is about restriction and instead reframes strength as a responsibility, something we actively build and protect over time.
Muscle, she argues, is not just for performance or aesthetics; it’s a critical organ that supports everything from blood sugar regulation to mobility and resilience.
The three buckets of muscle health
Lyon organizes skeletal muscle into three distinct categories, each serving critical functions. First, there’s the metabolic perspective. Healthy muscle mass provides a vital destination for glucose disposal, meaning metabolic diseases often originate in muscle tissue first. “The more healthy muscle mass you have, the greater place for glucose disposal,” Lyon explains.
The second bucket focuses on what she calls “the plumbing,” your cardiovascular system. Lyon and her husband recently published research demonstrating the connection between muscle mass, strength, and sexual function1. This relationship reveals how muscle health influences vascular function throughout the body.
Finally, there’s the strength and mass continuum. While hypertrophy (building muscle size) matters, so does developing functional strength. Lyon emphasizes that all three categories deserve attention, though the metabolic and vascular benefits often get overlooked in fitness conversations focused primarily on appearance.
Progressive stimulus, not just progressive overload
One of the most persistent myths in strength training is that you must constantly lift heavier weights to see results. Lyon challenges this notion, particularly for those in their 40s, 50s, and beyond, when muscles often gain strength faster than the tendons and joints that support them. This imbalance helps explain why injury risk tends to rise in midlife when training is driven solely by load rather than longevity.
Instead of relentless progression toward heavier loads, Lyon advocates for progressive stimulus—varying tempo, volume, and exercise selection to challenge muscles without compromising joint health. Your body adapts to how it’s stressed, not to arbitrary numbers on a bar.
This approach makes resistance training both safer and more sustainable over the long term, supporting muscle as a tool for metabolic protection, mobility, and resilience rather than short-lived performance gains.
Protein isn’t one thing—and that matters
When it comes to nutrition, Lyon is clear: dietary protein is the most important macronutrient. But protein isn’t a single entity. It’s made up of 20 amino acids, nine of which are essential and must come from the diet.
Leucine, in particular, plays a critical role in triggering muscle protein synthesis, the process that tells your body to build and maintain muscle. Without enough leucine per meal, you may be eating protein without fully stimulating muscle repair and growth. Lyon notes that around 2.5 grams of leucine per meal is the ideal target for adults.
Other amino acids matter too. Threonine supports gut lining integrity, while methionine contributes to antioxidant production through glutathione. This is why protein quality matters, not just total grams. Foods that contain all essential amino acids make it easier to meet these needs.
The GLP-1 conversation we need to have
Lyon acknowledges the tremendous benefit of GLP-1 medications for people struggling with obesity, but she’s concerned about an impending crisis. Research shows most people don’t stay on these medications beyond two years, and the weight they lose includes precious muscle and bone mass. When they regain weight off the medication, it typically returns as fat, essentially accelerating the aging process.
“We are trading one epidemic for another,” Lyon warns. While obesity posed serious challenges, the resulting sarcopenia (muscle loss) epidemic may prove even more difficult to address. Her protocol for anyone using GLP-1s is non-negotiable: resistance training, prioritized protein intake (including shakes and essential amino acids when appetite is suppressed), and potentially hormones like testosterone to protect muscle tissue.
The takeaway
If there’s one throughline in Lyon’s work, it’s this: strength is not for sale. It’s earned, built slowly through consistent training, adequate protein, and intentional habits.
And what makes Lyon’s approach empowering rather than intimidating is her insistence that there’s no single “right” way to train, just the commitment to consistent resistance work and adequate protein. You’re not building muscle for some distant future version of yourself. You’re building the capacity to show up fully, right now and for decades to come.
