Why Top Nutritionists Can’t Stop Talking About the Fibre-Muscle Link

The conversation about muscle preservation usually circles two pillars: lift weights and eat enough protein. That’s the prescription repeated in gyms, clinics, and countless health articles.

But a large-scale analysis of US health data suggests we’ve been overlooking a third pillar… dietary fibre.

The research

Between 2011 and 2018, researchers examined data from the US National Health and Nutrition Examination Survey. They focused on adults aged 40 and older, a group where muscle decline is not just common, but expected.

In total, over 6,000 participants had their diets, muscle mass, body composition, grip strength, and blood sugar measured. The question was simple: Is there a link between fibre intake and muscle health?

The answer was a clear yes, with an important caveat. This was an observational, cross-sectional study. It can’t prove that fibre directly increases muscle mass or strength. But it does show a strong and consistent association worth further investigation.

Participants with higher fibre intakes were more likely to have:

• More lean muscle mass (both total and in the limbs)

• Stronger grip strength

• Lower body fat (especially around the trunk)

• Better blood sugar control

And these findings held even after adjusting for age, activity level, and other factors.

Why fibre might matter for muscle

Fibre isn’t a muscle-building nutrient in the way protein is. Its role is more subtle, creating the right internal environment for the muscle to thrive.

The study and related research point to three possible mechanisms:

1. Gut health: Fibre feeds beneficial gut bacteria, which produce anti-inflammatory compounds that may help protect muscle tissue from age-related breakdown.

2. Metabolic stability: Fibre slows glucose absorption, improving insulin sensitivity and reducing energy crashes that can affect training and recovery.

3. Nutrient efficiency: A healthier gut environment may help the body absorb and utilise key nutrients, including amino acids, more effectively.

In other words, fibre may not build muscle directly, but it could help you keep it.

This isn’t a green light to overload on fibre. Suddenly doubling your intake can cause digestive issues, and more isn’t always better. Instead, the key message is: don’t treat fibre as an afterthought.

Aim for the recommended 25–30g per day from a mix of vegetables, fruit, legumes, whole grains, nuts, and seeds. Most adults fall short, averaging under 16g, so for many, simply closing that gap will make a difference without overdoing it.

Rethinking ageing-muscle

From the age of 40 onward, muscle mass naturally declines, a process called sarcopenia. By 60, the losses can accelerate, affecting mobility, strength, and independence.

Resistance training and adequate protein remain essential. But this research adds a new layer. If you want to maintain muscle mass, keep your fibre intake high.

More research is needed to confirm cause and effect, but the link is strong enough to pay attention to now.

The bigger picture

The fibre findings challenge a common assumption in both the fitness and nutrition worlds, that muscle maintenance is purely about training stimulus and protein supply. This research suggests the “support system” matters just as much.

If muscle is the engine, training is the ignition, and protein is the fuel, but fibre may be the oil that keeps everything running smoothly as the years go by.

The takeaway? Protect muscle and strength with age, focus not just on what you lift or how much protein you eat, but also on how much fibre you put on your plate.

Reference & Further Reading

Frampton J, Murphy KG, Frost G, Chambers ES. Higher dietary fibre intake is associated with increased skeletal muscle mass and strength in adults aged 40 years and older. J Cachexia Sarcopenia Muscle. 2021 Dec;12(6):2134-2144. doi: 10.1002/jcsm.12820. Epub 2021 Sep 29. PMID: 34585852; PMCID: PMC8718023.

Deehan, E.C., & Walter, J. (2016). The influence of dietary fiber on the gut microbiome. Critical Reviews in Clinical Laboratory Sciences, 53(5), 330–339. This is a foundational review that explains how fiber influences gut bacteria.

Marchesi JR, Adams DH, Fava F, Hermes GD, Hirschfield GM, Hold G, Quraishi MN, Kinross J, Smidt H, Tuohy KM, Thomas LV, Zoetendal EG, Hart A. The gut microbiota and host health: a new clinical frontier. Gut. 2016 Feb;65(2):330-9. doi: 10.1136/gutjnl-2015-309990. Epub 2015 Sep 2. PMID: 26338727; PMCID: PMC4752653.

Cruz-Jentoft AJ, Bahat G, Bauer J, Boirie Y, Bruyère O, Cederholm T, Cooper C, Landi F, Rolland Y, Sayer AA, Schneider SM, Sieber CC, Topinkova E, Vandewoude M, Visser M, Zamboni M; Writing Group for the European Working Group on Sarcopenia in Older People 2 (EWGSOP2), and the Extended Group for EWGSOP2. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing. 2019 Jan 1;48(1):16-31. doi: 10.1093/ageing/afy169. Erratum in: Age Ageing. 2019 Jul 1;48(4):601. doi: 10.1093/ageing/afz046. PMID: 30312372; PMCID: PMC6322506.

Dalle S, Rossmeislova L, Koppo K. The Role of Inflammation in Age-Related Sarcopenia. Front Physiol. 2017 Dec 12;8:1045. doi: 10.3389/fphys.2017.01045. PMID: 29311975; PMCID: PMC5733049.