Muscle & Metabolic Longevity: Why Muscle Is Your Longevity Currency
When people think about living longer, they often focus on heart health, brain function, or maybe cholesterol levels – but increasingly, one of the most powerful predictors of how well we age is hidden in plain sight: our muscle mass. Far beyond aesthetics or athletic performance, skeletal muscle plays a central role in how we regulate blood sugar, respond to stress, fight infection, and maintain the energy we need to move, think, and recover. It’s the biological engine that quietly powers dozens of systems at once – and as research is now confirming, how much muscle you carry in mid to later life could have a direct impact on how long, and how well, you live (1).
Muscle is what scientists call a metabolically active tissue – meaning it does far more than lift, push, or carry. It’s where your body disposes of most of the glucose from food, where amino acids are stored for emergencies, and where many of the cellular processes that determine resilience and vitality are regulated. And unlike fat or weight alone, muscle mass appears to provide a kind of “health buffer” that protects the body during illness, surgery, or times of inflammation. That’s why, increasingly, longevity researchers and clinicians are shifting focus: from tracking BMI or scale weight, to looking at relative muscle mass – a metric that tells us more about functional ageing, independence, and even risk of death (1).
This shift is backed by compelling data. In a large, long-term study of more than 3,600 adults aged 55 and older, researchers used bioelectrical impedance to accurately estimate skeletal muscle mass and calculated each person’s Muscle Mass Index (MMI) – essentially, how much muscle they carried for their height. Participants were tracked for over a decade, and the results were striking: those in the highest MMI quartile had a 20% lower risk of death than those in the lowest, even when controlling for blood pressure, cholesterol, glucose, inflammation, and waist size. Meanwhile, BMI – the metric most often used in doctor’s offices – showed no meaningful association with mortality (1).
Why does this matter? Because it reframes muscle as a critical organ of longevity, not a bonus or byproduct of fitness. It’s the tissue that keeps blood sugar stable, buffers the body during physiological stress, supports immunity, and reflects broader metabolic health. It also declines steadily with age – beginning as early as our 30s – unless actively maintained through resistance training and adequate protein intake. In other words, building and preserving muscle isn’t just about movement; it’s about keeping the systems that regulate life itself working longer, better, and more efficiently (1).
Sarcopenia and Strength Decline – What Happens With Age
Muscle loss isn’t something that only begins in old age – in fact, the process of sarcopenia, or age-related decline in skeletal muscle mass and strength, can begin quietly in your 30s and 40s. Defined by the progressive, involuntary loss of both muscle tissue and function, sarcopenia is now recognised as a major driver of frailty, falls, and metabolic instability in later life. While definitions vary, leading consensus groups recommend measuring not just muscle mass, but also strength and physical performance (such as walking speed or grip strength) to capture its full impact (2).
The numbers tell a sobering story: starting around age 50, most people lose 1-2% of muscle mass per year, which adds up to 3-8% per decade. Muscle strength declines even faster – about 1.5% annually between ages 50-60, accelerating to 3% per year beyond that. By the time someone reaches their 70s or 80s, they may have lost up to half of their original muscle mass, significantly reducing their strength, balance, and ability to recover from illness or injury (2).
This decline is driven by multiple biological changes. At the cellular level, there’s a loss of fast-twitch muscle fibres and a breakdown of the neuromuscular junctions that help the brain activate muscle. Hormone levels such as testosterone, estrogen, IGF-1 and DHEA naturally fall with age, lowering the signals for growth and repair. Chronic low-grade inflammation increases catabolism – the breakdown of tissue – while mitochondrial dysfunction, reduced satellite cell activity (needed for regeneration), and even apoptosis (programmed cell death) further degrade muscle integrity. These molecular shifts not only shrink muscle mass but also weaken its metabolic function(2).
The consequences reach far beyond strength. Sarcopenia is a key risk factor for frailty, reduced mobility, and fractures from falls. It also impairs glucose regulation, since skeletal muscle is the body’s main site for insulin-mediated glucose uptake. As muscle declines, the risk of insulin resistance and metabolic syndrome increases – creating a vicious cycle of fatigue, inflammation, and accelerated ageing (2).
The good news? These declines are modifiable. Regular resistance exercise has been shown to increase muscle protein synthesis even in the frailest nursing home residents. When combined with adequate protein and energy intake, the effects are significantly amplified. Interventions including leucine-rich protein, vitamin D supplementation, and even experimental medications targeting specific cellular pathways (like the angiotensin system) are showing promise (2). But even without pharmaceuticals, the combination of strength training and nutrition remains the most reliable, accessible and effective way to slow or reverse muscle loss.
Why Muscle Protects Your Metabolism
If you want to understand why muscle is often called “metabolic currency,” it helps to see it less as tissue and more as infrastructure. Skeletal muscle is the body’s single biggest site for glucose disposal; after you eat, around 80% of post‑prandial glucose uptake is handled by muscle through insulin‑dependent pathways. In practical terms, that means your muscles act like a glucose sink, pulling sugar out of the bloodstream and storing or burning it before it has a chance to linger and cause damage. When muscle mass is higher, the body has a larger “sink,” and when muscle mass is lower, that same glucose load has fewer places to go. The result is higher blood sugar exposure over time, greater insulin demand, and a drift toward whole‑body insulin resistance (3).
This matters because the paper makes a key point that is often missed in mainstream health advice: insulin resistance in skeletal muscle is sufficient to drive whole‑body insulin resistance. In other words, if muscle stops responding well to insulin, the metabolic consequences ripple outward, increasing the likelihood of chronic hyperglycaemia and type 2 diabetes progression. The mechanism is not vague. Glucose uptake in muscle depends on delivery of glucose to the tissue, movement of glucose transporters to the cell surface, and the ability of the muscle cell to process glucose once it enters. In type 2 diabetes, this system becomes impaired at multiple points; the timing and magnitude of muscle glucose uptake become blunted, which is one reason blood sugar remains elevated for longer after meals (3).
Where exercise becomes uniquely powerful is that it activates glucose uptake through pathways that do not rely solely on insulin. Muscle contractions stimulate GLUT4 translocation through signalling routes involving AMPK and calcium‑dependent mechanisms, meaning glucose can be taken up even when insulin signalling is impaired. Resistance training also increases total GLUT4 protein content in muscle, expanding the capacity for both insulin‑stimulated and exercise‑stimulated glucose clearance. That is why building and maintaining muscle is not just about appearance or strength; it is one of the most direct ways to improve glucose control, buffer post‑meal spikes, and reduce the metabolic strain that accelerates ageing across multiple organs. (3)
Protein, Strength and Daily Muscle Support
If muscle is a key to longevity, then protein is the tool that helps build and preserve it – especially as we age. But while the standard dietary guidelines still recommend 0.8 grams per kilogram of body weight per day, growing scientific consensus now sees that as too low for older adults. Based on clinical trials and expert group recommendations (including the PROT-AGE study group and ESPEN), the optimal intake to support muscle maintenance is closer to 1.2–1.6 g/kg/day – nearly double the traditional RDA. For an 80 kg adult, that means aiming for 96 to 128 grams of protein per day, split evenly across meals to maximise synthesis. Notably, one study found that just an increase of +0.54 g/kg/day over habitual intake led to measurable improvements in muscle mass – even without added exercise (4).
However, it’s not just the total amount that matters; when and how you consume protein is equally critical. Muscle protein synthesis (MPS) has a known per-meal threshold – around 0.4 g/kg, or roughly 25–30 grams of high-quality protein per meal in older adults. This plateau effect means simply “eating more at dinner” won’t cut it. A protein-rich breakfast (e.g., eggs and Greek yogurt), a balanced lunch with legumes or lean meat, and a nutrient-dense dinner with fish or tofu are all essential to maintain an even anabolic signal across the day (4).
Exercise amplifies these effects – and in many cases, resistance training and protein work synergistically to deliver better results than either alone. Just 2–3 sessions per week of weight-bearing or resistance work is enough to activate MPS pathways and stimulate gains. For older adults facing anabolic resistance, leucine-rich proteins (2–3g per meal) are particularly helpful in overcoming that barrier. Leucine triggers mTOR signalling, the pathway that drives new muscle protein synthesis, and combining this with omega-3 fatty acids has been shown to further enhance responsiveness through improved intracellular signalling (4).
Even light, consistent movement – walking, bodyweight squats, resistance bands – supports this system by keeping muscle tissue metabolically active and glucose-sensitive. That’s the real takeaway: preserving muscle isn’t about extreme gym routines; it’s about feeding your muscle with the right building blocks and sending it the signal to stay functional. The protein you eat, when you eat it, and the movement you pair it with, all combine to keep your muscle mass – and metabolic resilience – intact as you age (4).
Fibre + Protein = Metabolic Synergy
While protein and fibre each offer distinct health benefits, combining them creates a metabolic synergy that’s especially powerful for ageing bodies. A 2022 randomised controlled trial tested this concept directly by comparing a high-protein, high-fibre preload (20 grams protein + 6 grams fibre) to a low-protein, low-fibre version before meals in sedentary, overweight adults. The results were striking: the high-protein, high-fibre group showed significantly better appetite control, lower post-meal blood sugar spikes, and greater weight loss over 12 weeks – all while improving markers of insulin sensitivity (5).
Here’s why this works. Protein stimulates muscle protein synthesis by activating the mTOR pathway, especially when consumed in sufficient quantities (~20 – 30g per meal). This supports lean mass preservation – essential for metabolic health, glucose regulation and healthy ageing. Meanwhile, soluble fibre slows gastric emptying and carbohydrate absorption, resulting in 15–20% lower post-meal glucose levels compared to the low-fibre control. That stabilisation helps reduce insulin demand and metabolic stress on the pancreas, a benefit particularly relevant for older adults at risk of insulin resistance or type 2 diabetes (5).
But the real advantage is what happens when the two are combined. The study reported a 25–35% increase in satiety hormones like GLP-1 and PYY, both of which prolong fullness and curb overeating. Participants ate 12% less at their next meal and showed a larger increase in adiponectin, a hormone associated with improved insulin sensitivity. This means that even small dietary tweaks – like adding Greek yogurt with chia seeds before lunch or pairing eggs and oats at breakfast – can meaningfully influence appetite, body composition and blood sugar control over time (5).
In practical terms, this synergy turns everyday eating into a metabolic strategy. Fibre keeps blood sugar steady, protein supports muscle, and together they reduce overeating, improve hormone balance and protect long-term metabolic health – particularly for people over 40, when muscle mass naturally begins to decline (5).
Where FiiHii Frinks® Fit In
All the science in this article – from muscle mass as a predictor of survival, to protein-fibre synergy for blood sugar control and satiety – converges on one simple reality: longevity habits need to be sustainable. That’s where FiiHii Frinks® come in. Designed as functional, fibre- and micronutrient-rich smoothies, these blends offer a practical way to meet daily protein and fibre targets, especially for those juggling busy schedules or struggling with appetite, digestion or motivation as they age. They’re not just snacks – they’re precision-formulated nutritional tools that reinforce the exact longevity pathways discussed here.
Several Frinks shine especially brightly in this muscle-metabolic context. The Orchard Frink combines pectin-rich apples and pears with mineral-dense pumpkin seeds, delivering both soluble fibre to modulate post-meal glucose and plant-based iron, magnesium and zinc to support energy, muscle repair and insulin sensitivity. The P-Power Frink offers omega-3 ALA from flax, sorbitol from prunes, and a spectrum of antioxidants – supporting not only bowel regularity but also cardiovascular health and hormonal balance, which are increasingly important as lean mass declines with age. Meanwhile, the Traffic Light Punch Frink, with its combination of chia, berries and red grapes, delivers polyphenols, fibre and omega-3s in one vibrant package – a triple threat for inflammation control, blood sugar regulation and brain function.
Across the range, Frinks deliver the soluble and insoluble fibres, leucine-containing seeds, vitamin C, healthy fats and bioactive antioxidants that research links to better glucose control, stronger satiety signals, improved metabolic flexibility and enhanced muscle maintenance. Their structure makes them ideal as pre-meal preload options – mirroring the research-backed strategy of combining 20g protein and 6g fibre before meals to improve glucose stability, reduce food intake and support lean mass preservation in sedentary adults (5). Simply put, Frinks are a routine-friendly conduit for translating muscle and metabolic science into daily action – with no need for powders, prep or perfection.
Conclusion: Muscle as Longevity Currency
If we reframe muscle as not just strength or appearance, but as metabolic currency, the path to healthier ageing becomes clearer – and more empowering. Maintaining lean mass protects against blood sugar swings, inflammation, frailty and cognitive decline. And yet, most people lose muscle silently over decades, mistaking weight stability for health. This article shows that the combination of resistance training, protein intake, and fibre-rich whole foods isn’t a wellness cliché – it’s a clinically validated, physiologically sound strategy for extending both healthspan and functional independence.
Whether you’re in your 40s trying to stay ahead of metabolic decline, or in your 70s looking to preserve mobility and energy, muscle is the engine. It clears your glucose, supports your brain, and buffers your body through stress and illness. And that engine needs fuel: protein, fibre, micronutrients, movement – all of which can be integrated seamlessly into daily life with tools like FiiHii Frinks®. Small changes, sustained over time, yield exponential returns. Because in the game of longevity, muscle isn’t just a biomarker – it’s a strategy.
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References:
- Srikanthan P, Karlamangla AS. Muscle mass index as a predictor of longevity in older adults. Am J Med. 2014;127(6):547–553. doi:10.1016/j.amjmed.2014.02.007
- Walston JD. Sarcopenia in older adults. Curr Opin Rheumatol. 2012;24(6):623–627. doi:10.1097/bor.0b013e328358d59b
- Hulett NA, Scalzo RL, Jane. Glucose uptake by skeletal muscle within the contexts of type 2 diabetes and exercise: An integrated approach. Nutrients. 2022;14(3):647. doi:10.3390/nu14030647
- Kim D, Park Y. Amount of protein required to improve muscle mass in older adults. Nutrients. 2020;12(6):1700. doi:10.3390/nu12061700
- Glynn EL, Fleming SA, Edwards CG, Wilson MJ, Evans M, Leidy HJ. Consuming a protein and fiber-based supplement preload promotes weight loss and alters metabolic markers in overweight adults in a 12-week, randomized, double-blind, placebo-controlled trial. J Nutr. 2022;152(6):1415–1425. doi:10.1093/jn/nxac038
