How to build muscle & stay strong at any age: The surprising links between your gut health, strength training and healthy ageing | Prof Claire Steves & Prof Tim Spector

How do you build muscle and stay strong as you age?

For most of us, muscle loss starts in our 30s. It’s easy to think that you can combat this and stay strong into old age by strength training and eating plenty of protein.

Exercise and macros matter, but scientists are uncovering another important piece of the puzzle - a direct connection between your gut health and healthy ageing. It could change how we think about staying strong as we get older. 

In today's episode, Professor Claire Steves - a world-leading expert in ageing and health - and Professor Tim Spector explore the gut-muscle axis - how your gut microbiome influences your muscle health. They explain why maximum protein doesn't mean maximum muscle, how gut bacteria ‘talk’ to muscle tissue, and why an unhealthy gut can make muscles resistant to growth. 

For listeners looking for simple ways to support their muscles today, this episode includes practical advice you can easily fit into your routine. Claire and Tim share quick daily habits and explain how to get your protein from diverse plant sources. 

Could changing what you feed your gut microbes today be the key to keeping your body strong for decades to come?

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Timecodes

00:00 Intro

04:08 Why muscle matters for healthy aging, not just the gym

06:37 The hidden organ: how your muscles talk to your body

10:35 Why it gets harder to keep muscle as you age

11:37 Can you have a 20-year-old's muscles at 70?

13:29 Can muscle loss increase your risk of cancer?

15:51 Why skinny doesn't mean healthy

17:40 What is sarcopenia?

20:52 How 4 days of bed rest can shrink your muscles

23:31 Gut-muscle axis: how gut bacteria talk to your muscles

23:53 Why protein stops working as you age

26:11 Can improving your gut health build stronger muscles?

28:57 Can strength training change your gut microbiome?

30:57 Can the Mediterranean diet make your legs stronger?

34:01 The diet trial that improved muscle and bones, no gym

34:55 Is there a magic gut bug for building muscle?

39:38 Intermittent fasting: should you exercise before breakfast?

44:43 Can too much protein weaken your muscles?

46:32 How much protein do you really need per day?

49:20 The best protein foods to feed your gut and muscles

52:26 Carnivore diet: what meat and shakes do to your gut

53:46 Strength training, cardio or balance: what do you need?

56:04 The easy 2-minute toothbrush habit for better muscle health

57:21 Key takeaways: muscles, microbes, and the protein myth26:11 Can improving your gut health build stronger muscles?

📚Books by our ZOE Scientists

The Food For Life Cookbook

Every Body Should Know This by Dr Federica Amati

The Appetite Reset by Dr Federica Amati

Food For Life by Prof. Tim Spector

Ferment by Prof. Tim Spector

Good Mood Food (preorder) by Prof. Tim Spector

Free resources from ZOE

The Smart Snacking Guide: How to feed your gut, fuel your day, and snack without guilt

The Hormone Harmony Guide: Tuning Your Body’s Internal Orchestra  

Eating for Better Brain Health: Your brain-gut blueprint

How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health

Live Healthier: Top 10 Tips From ZOE Science & Nutrition

Gut Guide - For a Healthier Microbiome in Weeks 

Better Breakfast Guide

Mentioned in today's episode

Master Cyclist Study, King’s College London (2018)

Physical Activity and Reduced Cancer Risk, Nat Rev Cancer (2008)

Bed Rest and Muscle Loss, Diabetes (2016)

Microbiome Interventions and Inflammation, Cureus (2025)

The Gut Microbiome and Muscle Strength, BMC Geriatr (2021)

Resistance Training Reshapes the Gut Microbiome, Sports Med Open (2026)

The Mediterranean Diet and Muscle Strength, Physiotherapy Theory and Practice (2025)

Short-Chain Fatty Acids and Muscle Mass, J Cachexia Sarcopenia Muscle (2024)

Mitochondrial Properties in Skeletal Muscle Fiber⁠, Cells (2023)

Episode transcripts are available here.