Why muscle mass matters in keeping weight off long term

When talking about maintaining weight loss, the conversation often centres on the number on the scales. But many reach their goal weight only to find they're feeling weaker, less energetic, or struggling with everyday things that used to feel easier, whether that's carrying the shopping, keeping up with the kids, or staying active throughout the day.

That's where muscle mass comes in. During maintenance, preserving and building muscle can help support your strength, mobility, energy levels, and long-term health. In fact, looking after your muscle mass can be an important part of protecting the progress you've worked so hard to achieve. In this guide, we'll explore why muscle matters during maintenance and the simple habits that can help you hold onto it for the long term.

Key points

• Muscle mass is an important part of weight maintenance, helping to support your strength, mobility and overall health.
• Some muscle loss can happen during weight loss, but getting enough protein and including strength-based exercise can help protect it.
• Focus on building healthy habits, not hitting a perfect number. Maintaining or improving your muscle mass relative to your own goals is what matters most.

What is muscle mass?

Muscle mass is a fancy term for the amount of muscle tissue in your body. It includes your skeletal, smooth, and cardiac muscles. Your muscle mass makes up only one part of your overall body composition, because your body is also made up of fat, bone and water.

What is skeletal muscle mass?

When people talk about muscle mass, they're usually referring to skeletal muscle mass. These are the muscles attached to your bones that help you move, maintain your balance, and carry out everyday activities, from walking up the stairs to lifting shopping bags.

Skeletal muscle does much more than support strength and mobility. It also plays an important role in long-term weight maintenance, which is why preserving muscle during and after weight loss is so important.

" Protecting your muscle mass plays an important role in weight management. Skeletal muscle supports movement, strength, and day-to-day function. It can help you stay active, support your health, and make it easier to maintain your weight over time."

Ayesha BashirPrescribing Pharmacist

Muscle mass percentage explained

Muscle mass percentage is the portion of your total body weight made up of muscle.

Even though body weight is typically used in healthcare assessments, there is scientific evidence to suggest that body composition measurements are a better indicator of your overall health than body weight alone. This is because they account for differences in the proportion of fat and fat-free mass that vary naturally between different people.

For example, these proportions can vary by sex and age, and are determined by multiple factors, including your genetics and activity levels. In short, body composition accounts for the fact that two people of the same height and body weight can look completely different due to having different body compositions.

Why muscle mass matters for weight maintenance

Your muscles support all your bodily functions, helping to control your heartbeat, breathing and digestion, among other things. However, your muscle tissue is also metabolically active, meaning it burns calories, even when you’re not moving. This is why people with more muscle mass tend to have higher basal metabolic rates (BMR). As a result, your muscles also play an essential role in helping you maintain your weight.

Can weight loss lead to muscle loss?

Yes, when you lose weight, alongside fat, you can also lose some muscle mass, particularly if you’re losing weight quickly, not eating enough protein, or not doing any strength-based exercise.

This is why preserving muscle should be a priority throughout both weight loss and maintenance. Muscle plays an important role in supporting strength, mobility and overall health, and it can also make it easier to maintain your weight in the long term because muscle tissue requires more energy to preserve at rest than fat tissue. Put simply, the more muscle mass you have, the more calories your body naturally burns throughout the day to maintain it, even when you're not doing anything active.

If you're using weight loss medication, paying attention to your protein intake as part of a balanced nutrition becomes especially important. Medications such as Wegovy, Mounjaro, and Foundayo can reduce your appetite, which means you may naturally eat less. While this can support weight loss, it can also make it harder to get the nutrients your body needs to protect muscle mass if you're not eating a balanced diet.

Signs you may be losing muscle mass

If you've lost weight, it isn't always easy to tell whether you've lost muscle mass as well. While some people notice that their muscles appear less defined, there are other signs of losing muscle mass, including:

• feeling weaker than usual
• finding everyday activities, such as carrying shopping or gardening, more challenging
• struggling with exercises that previously felt manageable
• feeling less stable, balanced or mobile

It's important to remember that these signs don't always mean you're losing muscle mass. They can sometimes be linked to other health conditions or changes in your overall health. If you're concerned about a loss of strength, mobility or muscle mass, speak to a healthcare professional for personalised advice.

What is a good muscle mass percentage?

There isn't one "ideal" muscle mass percentage that everyone should aim for. What's considered healthy can vary depending on factors such as your age, sex, body size, genetics, and activity levels.

For example, someone who regularly does strength training is likely to have a higher muscle mass percentage than someone who is less active, and that's perfectly normal. Muscle mass also tends to change naturally throughout life, with many people gradually losing muscle as they get older.

Rather than focusing on reaching a specific number, it's often more helpful to think about whether you're maintaining or improving your muscle mass relative to your own circumstances and goals. Building or preserving muscle can support your strength, mobility, metabolism, and overall health, regardless of the exact percentage.

Average muscle mass for women and men

Men and women naturally tend to have different amounts of muscle mass, but there's no single figure that's considered "normal" for everyone. Your muscle mass is influenced by a range of factors, including your age, genetics, body size, activity levels, and overall health.

On average, muscle makes up around 40% of total body weight, although this can vary significantly from person to person. Rather than comparing your muscle mass to someone else's, focus on what you can do to support your own muscle health.

How can you check your muscle mass?

Most widely available muscle mass calculators are a rough estimation. For a more accurate picture, there are various types of imaging tests that can measure your muscle mass. However, they are typically expensive and can produce different results, even for the same individual. Options include:

• magnetic resonance imaging (MRI)
• dual-energy X-ray absorptiometry (DEXA)
• bioimpedance analysis
• D₃-creatine dilution
• computed tomography (CT)
• ultrasound

It’s perhaps more important to measure your muscle strength, as this will help you stay active and able to perform your daily activities. A healthcare professional can help you do this using a hand dynamometer, which measures handgrip strength, which is a good indicator of overall muscle strength.

How to increase muscle mass during maintenance

Here are some of our top tips for maintaining and even increasing your muscle mass while maintaining your weight:

• Prioritise protein: Eating plenty of protein can help to maintain your muscle mass, even when you’re eating less overall. Good sources of protein include meat, eggs, fish, beans and peas, nuts and seeds.
• Include strength training: Resistance training can help you preserve your current muscle mass and improve your muscle strength. It works by making your muscles work against a weight or force. Thankfully, you don’t need to go to a gym to do resistance exercises. Examples you can do at home include wall press-ups, biceps curls with a weight, resistance band exercises.
• Stay active overall: While resistance training is specifically good for maintaining and building muscle mass, staying active in other ways can help to maintain your overall health. For example, flexibility exercises, like yoga, tai chi and Pilates, can help your joints maintain the movement they need to support your everyday tasks.

Muscle plays a key role in weight maintenance

The number on the scale is only a small part of the maintenance phase. Feeling strong, capable, and able to enjoy the life you've worked hard to build is the bigger picture, and your muscle mass is key. Habits like eating enough protein and staying active can help support your strength, mobility, and long-term health as you move through maintenance.

And while muscle is an important part of the picture, it as well is another piece of the successful weight maintenance puzzle. For more practical advice on the habits, mindset shifts, and everyday strategies that can help you maintain your results with confidence, explore our complete guide to long-term weight maintenance.

FAQs

Why is muscle mass important for weight maintenance?

Muscle helps support your strength, mobility, and overall health. It also uses more energy to preserve, even when you're resting, which is why it can support long-term weight maintenance.

Can you lose muscle when losing weight?

Yes. Weight loss usually involves losing a combination of body fat and muscle. Getting enough protein and including strength-based exercise can help reduce muscle loss during your weight loss journey.

How do I know if I've lost muscle mass?

You may notice you're feeling weaker, finding everyday activities more difficult, struggling with exercises that used to feel easier, or feeling less stable and mobile. However, these signs can have other causes too, so speak to a healthcare professional if you're concerned.

Does more muscle mean I burn more calories?

Muscle tissue is metabolically active, meaning it requires energy to maintain. People with more muscle mass generally burn more calories at rest than those with less muscle mass, although many factors influence metabolism.

What is a healthy muscle mass percentage?

There isn't one ideal number for everyone. Muscle mass naturally varies depending on your age, sex, genetics, body size, and activity levels. It's often more helpful to focus on maintaining or improving your muscle mass relative to your own goals.

How can I maintain muscle while maintaining my weight?

Prioritising protein, doing regular strength-based exercise, and staying active overall can all help support muscle maintenance. Consistency is usually more important than following a perfect plan.

Does weight loss medication affect muscle mass?

Weight loss medications can reduce appetite, which may make it easier to eat less overall. That's why it's especially important to focus on balanced nutrition and adequate protein intake while using treatments such as Wegovy, Mounjaro, or Foundayo.

Is muscle more important than the number on the scales?

Both can be useful, but the scales only tell part of the story. How strong, healthy, energetic, and capable you feel in everyday life is important too, which is why muscle mass is such an important part of long-term weight maintenance.

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