If you’ve ever experienced the scale creeping up after you start hitting the gym, you’ve likely wondered whether the gain is from fat or muscle. 

While 1lb of fat and 1lb of muscle weigh the same amount, they can look, feel, and act very differently. Understanding fat vs. muscle (and how to go about gaining muscle or losing fat) comes down to the differences in how these tissues behave in our bodies. 

In this blog, we’ll get to grips with muscle and fat and answer some of your body composition FAQs. Is muscle denser than fat? Can you turn fat into muscle? Is it possible to lose fat and gain muscle at the same time? Stay tuned to find out. 

Muscle vs. Fat Compared

Fat vs. muscle: A hand-drawn, fibrous pink muscle tissue is labelled "muscle" next to a yellow, globular fat tissue labelled "fat".

Getting to grips with body composition starts with understanding the basics. Let’s take a look at the differences between fat vs. muscle and the role they play in the body.  

Muscle mass

What is muscle? 

Muscle is a soft tissue that plays a variety of roles in the human body. Muscle supports both voluntary movement (such as daily activity or exercise) and involuntary movement (such as the heart pumping blood). 

Muscle in the human body comes in three forms

  • Skeletal muscle (that facilitates movement)
  • Cardiac muscle (in the heart)
  • Smooth muscle (in the intestines)

When it comes to body composition, we’re talking about skeletal muscle. Skeletal muscle is involved in voluntary movement, supports the skeleton, and is the type of muscle that you can gain through intentional strength training. If you’re reading this with the goal of gaining muscle mass, this is the type of muscle you’re thinking of!

Benefits of muscle mass

Muscle plays a crucial role in optimal body composition, overall health, and even longevity. Some benefits of having higher muscle mass include:  

Looking to build muscle mass? Check out our guide to building lean mass to get started. 

Fat mass

What is fat? 

Adipose tissue, more commonly known as fat, is a connective tissue found throughout the human body. The main role of fat is as an energy store: fat cells store energy when it isn’t needed, and release it when it is. Fat is also a key part of the endocrine system, producing and interacting with a variety of hormones, and affecting your metabolism.  

There are a few main types of fat: 

  • Subcutaneous fat (found under the skin)
  • Intramuscular fat (found inside skeletal muscle fibres)
  • Visceral fat (found around the internal organs) 

Visceral fat is a particularly important metric when it comes to body composition. High levels of visceral fat (even in individuals who have an ideal overall body fat level) are linked to a range of health concerns, including an increased risk of cardiometabolic conditions. 

For more information on visceral fat and body fat in general, check out our guide to a healthy body fat percentage

Risks of high body fat

Fat is an essential tissue and necessary for survival. However, high levels of body fat can have a significant impact on our overall health. 

Having a higher body fat percentage can increase the risk of: 

Maintaining a healthy body fat percentage and maintaining (or building) muscle mass can help to decrease your risk of these health concerns. If you’re looking to lose fat, then there are plenty of healthy ways to do so. You can check out our post on how to lose body fat for more info. 

Should I track my weight or body composition?

Whether you choose to track your weight, body composition, or both will depend on your health and fitness goals. 

If your primary goal is to lose weight, then obviously your weight is going to be a key metric to track. However, it may also be beneficial to track other metrics such as your body fat percentage and overall muscle mass to understand how your weight loss is progressing. Not all weight loss comes from fat, and losing muscle (or experiencing symptoms such as brain fog or frequent illness) could be a sign that your calorie deficit is too large. 

If your main goal is to gain muscle, then your weight may not be the most useful metric. Any increase on the scale could be fat, muscle, or likely a combination of the two, and won’t give you much insight into your gains. In this case, it makes more sense to invest in a form of body composition tracking.

Whatever your goal, tracking your body composition can be a useful way to keep tabs on your overall health. There’s really no downside to better understanding your body composition and how this changes over time.  


Fat vs. Muscle FAQs

A young caucasian woman with a perplexed look on her face sits cross-legged on a blue yoga mat. She is wearing gym clothing and a water bottle sits in front of her.

There’s plenty of misinformation out there about body composition, but understanding your body composition doesn’t need to be complicated. Let’s take a look at some common body composition FAQs. 

Does muscle weigh more than fat?

The idea that muscle weighs more than fat is a body composition myth. However, like many myths, the idea that muscle is heavier than fat is rooted in something true – in this case, that muscle is denser than fat. 

This means that while 1lb of muscle and 1lb of fat weigh the same amount (1 pound is a pound!) the 1lb of muscle is denser than the 1lb of fat. Muscle takes up less space than fat. This is why two people of the same weight and height can have drastically different builds. More muscle mass contributes to a slimmer, leaner look than the equivalent quantity of fat mass.  

Can fat turn into muscle?

Unfortunately, fat can’t turn into muscle – at least not directly. 

Fat and muscle are distinct tissues that are made up of different types of cells, and one can’t transform into the other. Building muscle is a separate process from burning fat, and the fat we burn gets used for energy – not built into new muscle. 

In fact, too extreme of a fat loss regime can result in the loss of muscle, too, impacting strength, metabolic rate, and further fat loss. If you’re on a weight loss journey, you can mitigate this muscle loss by sticking to an appropriate caloric deficit, getting plenty of high-quality protein, and incorporating resistance or strength training into your workout routine. 

How do I know if I’m gaining muscle or fat?

You’ve gained weight. How do you know if it’s muscle or fat? 

The best way to assess any change in your body composition is through a professional DEXA scan. Simply weighing in won’t tell you whether you’ve gained muscle or fat – and can even feel discouraging if you’ve started strength training and are seeing your weight creep up. 

Similarly, while a home smart scale can give you an estimate of your body fat percentage or changes over time, this isn’t a particularly accurate way to check in on your body composition. A DEXA scan can provide accurate measurements of your fat mass, muscle mass, and visceral fat, as well as show you where you’re carrying more fat or muscle. 

If you’re looking for a quick sense of whether you’re gaining muscle or fat, there are some signs you can notice at home. If your weight gain is mostly from fat, you may notice a “softer” look to your body, and less visible muscle definition. Your clothes may fit a little tighter, since fat takes up more space than muscle. 

Similarly, if your weight gain is mostly from muscle, you may notice a leaner look to your body, or that your clothes fit a little looser. You may also feel stronger, or notice that you can lift heavier, easier, or for more reps.  

If you’re finding it hard to notice any changes in the mirror, keeping track of measurements at home can be a great way to estimate how your training is progressing. As always, checking in on how you feel – both in your day-to-day life and while working out – is an important metric to keep an eye on. 

I’m gaining weight – why do I look thinner?

If you’re regularly strength training, noticing the scale tick up, and seeing a leaner reflection, you may be gaining muscle mass. 

As we mentioned earlier, muscle is denser than fat – it takes up less space than the equivalent weight in fat. Body composition changes may mean you notice you appear slimmer or leaner, or that your clothes feel looser while seeing the same – or even a higher – weight on the scale. 

Tracking your body composition over time will give you significantly more insight into your fitness progress than tracking your weight alone. 

Can I gain muscle and lose fat at the same time?

No, you can’t usually gain muscle and lose fat simultaneously. This comes down to the fact that while building muscle requires a calorie surplus, losing fat requires a calorie deficit.

If you’re completely new to strength training, you may find that you’re able to defy this rule by losing fat and building muscle simultaneously – at least for a while. As you start to lift weights, you may be rewarded with a sudden increase in strength while experiencing fat loss. However, these “newbie gains” tend to subside as your body adapts to the new type of exercise. 

For most regular gym-goers, it’s necessary to focus on one goal at a time (or to incorporate both into a bulk and cut cycle) to gain muscle and lose fat. Under specific circumstances, it can be possible to gain muscle and lose fat at the same time, but this process can be quite technical and difficult to achieve. 

If I cut more calories, will I lose more fat?

Weight loss, including fat loss, requires a calorie deficit. This means that to lose body fat you need to be taking in fewer calories than you’re expending through everyday activity and exercise. 

With this in mind, it’s a common misconception that cutting calories further will automatically equate to a faster rate of fat loss. While maintaining a caloric deficit is required to lose fat, increasing this deficit can actually have the opposite of the desired effect. 

When we create a caloric deficit, that energy has to come from somewhere. Ideally, this is from excess body fat. However, if we create too large of a deficit, the body may draw this energy from elsewhere. This could be from muscle tissue (which is “expensive” to maintain), limiting energy spent on immunity (increasing the chance of infection), or limiting energy for high-energy brain function (resulting in brain fog and difficulty concentrating). If you’re experiencing these symptoms, then it may be a sign that your calorie deficit is too high. 

In all of these instances, a greater calorie deficit wouldn’t result in any more fat loss than a smaller deficit. An ideal deficit will depend on factors such as your age, starting weight, and body fat percentage, but aiming for a deficit of approximately 500 kcal is a good place to start. 

What is the best way to measure my body composition?

There are a variety of ways to measure (or estimate) your body composition. Here’s an overview of the most popular ways to assess your body composition: 

    • DEXA scan: The gold standard in body composition analysis, a DEXA scan is a safe, accurate, and detailed way to assess your body composition. 
    • Bioelectrical impedance analysis: BIA estimates your fat-free mass based on a measurement of body water. While not as accurate as a DEXA, this can be a good way to track trends over time. 
  • Skin calipers: Skinfold calipers are an accessible manual tool for quickly measuring body fat at specific parts of the body, or estimating overall body fat.

A DEXA scan is the best way to accurately measure your body composition, but other methods can prove valuable for more regular or at-home tracking. You can read more about the types of health and fitness testing here

Want to optimise your body composition?


A group of three young adults are casually gathered in a gym, two crouching and one sitting. They are all wearing workout attire and smiling, perhaps sharing a joke or celebrating a win.

Hopefully, this article has left you with fewer questions about fat vs. muscle and the role these tissues play in your body composition. 

If you’re looking to gain muscle or lose fat, getting an accurate assessment of where you’re starting from can be invaluable. A professional DEXA scan is the gold standard in body composition assessment and the best way to measure your body fat percentage

To find out more or to book your free fitness and nutritional consultation, reach out to My Vital Metrics today!