How much muscle mass should you have – and how do you measure it?
Muscles aren't just for those who want to look fit. After 50, they're about something much more mundane: being able to carry grocery bags, get up from an armchair without support, and keep your balance when you trip on a curb. The only question is how much muscle mass you actually need – and whether you can even measure it. The answer is more honest than most health websites want to admit.
Muscle mass and fat-free mass are not the same thing
The body is usually divided into two parts: fat mass and fat-free mass. Many people use “fat-free mass” and “muscle mass” as if they were synonyms, but that’s not true. Fat-free mass includes everything that isn’t fat bones, skin, organs, and the water you carry around. Muscle is just one part of it.
When we talk about muscle mass, we mean the weight and volume of the body's muscle tissue. There are three types: skeletal muscle, smooth muscle in internal organs, and heart muscle. In practice, almost everyone is referring to skeletal muscles the ones that are attached to the skeleton and that you control yourself. They are the ones that allow you to walk, lift, keep your back straight, and maintain balance.
What do the numbers say?
Here's the first inconvenient truth: there are no official guidelines for how much muscle mass a person should have. Measurements are influenced by height, gender, age, exercise habits, diet, and genetics. As a rule of thumb, skeletal muscle makes up about 40 percent of an adult's body weight.
The average figures circulating online are largely based on a study from 2000 in which just under 500 adults were measured and divided into age groups. The data is therefore both small and old. Use the tables as a rough reference – not as a grade.
Average muscle mass – men
Age | Percentage of muscle mass |
18–35 years old | 40–44% |
36–55 years old | 36–40% |
56–75 years | 32–35% |
76–85 years | below 31% |
Average muscle mass – women
Age | Percentage of muscle mass |
18–35 years old | 31–33% |
36–55 years old | 29–31% |
56–75 years | 27–30% |
76–85 years | below 26% |
Notice the pattern in the tables: the curve points downwards over the years. This is the development that can be influenced – and which this article is really about.
How to measure muscle mass – harder than you think
Getting your exact muscle mass requires equipment that most of us never have access to. Methods used in research include magnetic resonance imaging (MRI), DEXA (a low-dose X-ray that breaks down the body into fat, muscle, and bone), computed tomography (CT), ultrasound, bioimpedance (a weak current sent through the body), and a tracer method called D3-creatine dilution.
Imaging diagnostics is usually called the “gold standard”. But even the best methods give different answers on the same body. In a comparison between the creatine method and an MRI, the results varied from 0.6 kilos lower to over 13 kilos higher. Thirteen kilos of muscle in measurement error – that says something about how careful one should be with exact figures.
At home and at the gym, body composition is instead measured, i.e. the distribution between muscle, fat, bone and water. Common options:
• Body analysis scale with bioimpedance
• Waist and hip measurements with measuring tape
• Calipers that measure skin folds
• Underwater weighing
• Online calculators
None of them come close to the precision of an MRI. But they have one advantage that research methods lack: you can repeat them often. And it's the change over time that's interesting, not the decimals. Measure in the same way, at the same time of day, and compare to yourself.
Is it better to have a lot of muscle?
Yes, with a few exceptions. From around the age of 40, the body begins to lose muscle mass on its own – a process called sarcopenia. Without countermeasures, this can be up to eight percent per decade, and the rate increases with age. Sarcopenia means not only smaller muscles, but also poorer quality, function and strength in the muscles that remain.
The consequences are concrete: increased risk of falls and fractures, poorer recovery after surgery and a clear link to, among other things, type 2 diabetes, cardiovascular disease, osteoporosis, kidney and liver disease and shortened lifespan. Low muscle mass is also common in obesity you can have both too much fat and too little muscle at the same time.
There is also research that suggests that preserved strength and muscle mass are linked to better cognitive function and mental well-being. The evidence is still thin here, so take it as a likely bonus rather than a promise.
Disadvantages? They are modest. A lot of muscle can make it harder to find clothes that fit well, and you need to eat more to feel full. Some also find that mobility is reduced but that is a question of how you train, not whether the muscles themselves are a problem.
How to build muscle mass
Two things do the job: load and food. The rest is details.
Strength training whether you use dumbbells, machines, bands, or your own body weight builds muscles by forcing them to work against resistance. Aim for at least two workouts a week that cover the body’s major muscle groups: legs, back, chest, shoulders, arms, and core. Bench press-ups, weightless squats, and chair raises are all good places to start. You don’t need a gym membership to get started.
Diet determines whether your training will yield results. Protein builds and repairs muscle tissue, and the need increases rather than decreases with age because the body uses protein less efficiently. Good sources include meat, poultry, fish, eggs, dairy products, beans, lentils, and nuts. Spread your protein out over the course of the day rather than putting it all in at dinner.
Carbohydrates are not the enemy – they provide the energy that allows you to train hard enough for your muscles to respond. Choose slow, high-fiber options over white bread and sugary drinks. You also need enough fat, vitamins, and minerals. The more of your food that comes from ingredients you recognize, the less you need to think about the rest.
In conclusion
Muscle mass is part of your fat-free mass, and as a rule, more muscle means a lower risk of injury, disease and premature death as well as better mobility and balance in everyday life.
But calculating your exact muscle mass is difficult. The most accurate methods are expensive, and even they are spread out. If you want a useful measure at home, body fat percentage combined with how you perform how many sit-ups you can do, how heavy you can lift, how sure you are on one leg – is much more valuable than a number on a scale.
The good news is that you don't need to know your muscle mass to improve it. The body responds to stress at any age. It's never too late to start – but it's never easier than today.
Three things you can do this week
• Schedule two strength training sessions in your calendar. Not “when I have time” one day and one time.
• Add a source of protein to breakfast. It's the meal most of us eat the least of.
• Do a simple exit test: get up from a chair without using support as many times as you can in 30 seconds. Write down the number and repeat the test in a month.
Want to get started?
In the Bodyweight Diet app, you train with your own body weight at home, without equipment and at a pace that suits a body over 50. Download the app and try our free 7-day program, and you will get strength training, a diet plan and a plan to follow from day one.
All the best, Kennet Båth
The content is general information and does not replace individual medical advice.
