There are three types of muscle²:

• Skeletal (the muscles you can see and flex)²
• Smooth (found in organs like your stomach and blood vessels)²
• Cardiac (your heart)²

Skeletal muscle represents around 40% of your total body mass.² It plays an important role in key biological processes, from storing nutrients to stabilising joints.³ A lower muscle mass can affect day to day living in a number of ways, including difficulty climbing the stairs,⁴ or getting up from a chair,¹⁶ and an increased risk of falls and bone fractures.⁴

The link between obesity and reduced muscle mass is complex, with several biological processes involved.^5,6 What we do know is that those living with obesity often have increased muscle mass,¹ but the muscle quality may be lower,¹ leading to reduced strength and power.¹ This can have a negative impact on physical performance, particularly as you age.^1,4

During weight loss, the aim is to lose fat while preserving muscle. Multiple techniques can be used to measure whether you are reducing your fat mass, rather than muscle mass.⁷
You may already be familiar with the Body Mass Index (BMI) calculator, as this tool is traditionally used to measure body weight in relation to your height.¹⁷ However, BMI does not differentiate between fat mass and lean mass and does not take into account body fat distribution.⁸ As muscle is denser than fat,¹⁸ somebody with a muscular body may have a high BMI, while a lean person with a ‘normal’ BMI may actually carry a great deal of body fat. ⁹ This is why a combination of tools is recommended for use alongside BMI, including Waist-to-Height ratio, body composition scales or even MRI. ^7,10

Maintaining muscle mass while losing weight may sound daunting but there are practical ways to help make it feel more manageable. Two key factors can make a significant difference: regular physical activity and prioritising protein in the diet.¹ Together, these can increase your basal metabolic rate (BMR), which is the number of calories your body needs to function at a basic level. This means that you will burn more calories when you are at rest.¹¹

Resistance training (also known as strength or weight training) is a great way to improve muscle strength.¹ Examples include:

• Free weights¹²
• Dumbbells weight-training machines¹²
• Working with elastic resistance bands¹²
• Body weight exercises such as push-ups, sit-ups or squats¹²

You can start off with simple resistance training exercises at home.¹² For example, if you do not have weights or dumbbells, use filled water bottles or cans.¹² It is generally advised to start slowly and build up the intensity of resistance or weight activity gradually.¹⁹

Increasing protein intake can help to retain and increase muscle mass in adults with overweight or obesity.¹⁴ Intake of more than 1.3 g/kg/day is needed to increase muscle mass.¹⁴ An added benefit is that protein-rich foods keep you feeling fuller for longer.²¹ Protein-rich foods should be consumed across three meals per day and include fish, chicken, eggs, meats and cheese.¹⁵ Plant-based options include beans, lentils, peas (black-eyed or split) and tofu.¹⁵

It’s important to remember that losing weight is not just about reducing the number on the scale, it’s about improving health while protecting the muscle that supports strength, mobility and long-term wellbeing.

By combining regular resistance-based activity with a protein-rich, balanced eating pattern, you can better preserve (and even build) muscle as you lose fat.¹ If you’re unsure where to start, speak to your doctor for personalised guidance and support.