When you start a new resistance training program, you may notice that your body is getting bigger and your weight is increasing. Well-meaning friends may try to convince you that your weight gain is due to increased muscle, but that may not always be the case. Some of your extra weight may also be from fat.
But what are the differences between muscle and fat? The differences between muscle and fat are that muscle is contracticle (meaning it drives our bodies’ movements and produces force) and more metabolically active (meaning it burns more calories than fat). Muscle is also denser, so it takes up less space in the body than an equal amount of fat.
Understanding the differences between muscle and fat is important. As your body changes from following a consistent workout plan, being able to tell if you’re gaining fat or muscle can indicate how close you are to meeting your body composition goals.
In this article, I’ll discuss:
- The differences between muscle and fat
- Whether muscle weighs more than fat
- Whether gaining muscle will make you gain weight
- How to tell if you’re gaining muscle or fat
- The ideal muscle to body fat ratio and body fat percentages for men and women
Looking for a workout routine that can help you build muscle? Check out Fitbod. It automatically creates a workout routine based on your goals, schedule, and available equipment. It also provides recommendations on how to add more cardio to your routine, which can help you burn more calories and keep body fat low. Download the Fitbod app today for free workouts.
What Are the Differences Between Muscle and Fat?
The main differences between muscle and fat are that:
- Muscle is contractile, while fat is not
- Muscle is more metabolically active than fat
- Muscle is denser than fat
Muscle Is Contracticle, While Fat Is Not
Muscle is contractile tissue, meaning it produces motion. Anytime you stand up from a chair, bend over to pick something up, or lift something to put it away on a high shelf, your muscles drive those actions.
Muscle is also responsible for force and power output. More lean muscle mass allows you to do things like jump higher or move heavy objects at a faster pace.
On the other hand, fat is not contractile. It provides energy but doesn’t allow you to move more powerfully or exert more force when lifting heavy weights. In fact, studies show that having larger percentages of body fat decreases skeletal muscle function and mobility.
As such, while weighing more often means you can lift more weight, that extra weight won’t necessarily translate to increased strength if a high percentage of it is from fat.
Muscle Is More Metabolically Active Than Fat
Being more metabolically active means muscle burns more calories than fat, even at rest.
Your body burns calories all day long from performing life-sustaining functions like pumping blood and from exercise and non-exercise activities. Muscle mass can contribute to your total daily calorie burn. Studies show that each pound of muscle burns up to seven additional calories per day. In comparison, fat only burns about two calories per pound.
Muscle Is Denser Than Fat
Muscle has a higher density than fat, meaning it takes up less space than an equal amount of fat. Studies show that fat has a density of about 0.9g/cm3, and muscle has a density of 1.06g/cm3.
This means if you put one pound of muscle and one pound of fat on a scale, there would be more fat than muscle.
Does Muscle Weigh More Than Fat?
Muscle does not weigh more than fat. One pound of fat and one pound of muscle weigh the same – one pound.
The misconception that muscle weighs more than fat comes from the fact that, as mentioned earlier, muscle is denser than fat. If you were to fill two separate bowls, one with fat and one with muscle, you would need more muscle to fill its bowl. It’s similar to how you would need a lot more feathers to fill a box with one pound than if you were filling a box with paper.
This is why someone who weighs 150lbs and has a high percentage of lean muscle mass can look smaller than someone who also weighs 150lbs but doesn’t have as much lean muscle.
Will Gaining Muscle Make You Gain Weight?
Gaining muscle can make you gain weight. You have to eat in a calorie surplus to build muscle, and since you’ll be eating more calories than you burn, your weight will increase.
But it’s important to note that some fat gain is inevitable when you put on muscle mass. If you gain 5lbs in a month, only about 1-2lbs may be from muscle. The amount of muscle you gain in a month can be higher if you’re a beginner or have a high body fat percentage, but it will be lower if you’re more experienced or already naturally lean.
Related Article: How Much Muscle Can You Gain in a Month?
However, you can minimize the amount of fat you gain by eating in a conservative caloric surplus (about 150-200 calories more than you need to maintain your body weight). Doing 20-30 minutes of low-impact cardio 2-3 days per week and getting at least 7,000 steps per day can also help keep fat gain to a minimum.
It’s also important to note that you may notice rapid increases in weight when you first start resistance training or begin a new high-volume training block.
But this doesn’t mean you’ve suddenly gained a bunch of muscle in just a few short days. It’s more likely due to increased inflammation and water retention as your body repairs the muscle damage you inflict from resistance training.
Your weight should return to normal as you settle into a new workout routine. It can also go back down when you take a deload week with decreased volume, which you should do every 6-8 weeks.
How to Tell if You’re Gaining Muscle or Fat
Since increased muscle mass and fat can both make you look bigger, it can be difficult to determine if you’re gaining muscle or fat. Below are some ways you can tell if your weight and size increases are coming from muscle or fat.
Signs You’re Gaining Muscle
You’re Gaining Weight But Losing Inches
As I mentioned earlier, muscle is denser than fat and takes up less space in the body. If your weight on the scale is going up, but you look leaner in photos, you’re likely gaining muscle and losing fat (a process called recomping).
You’re Getting Stronger in the Gym
Increased strength is a good indicator that you’re gaining muscle. Because muscle is contractile tissue and fat is not, more fat mass doesn’t necessarily translate to increased performance in the gym. But if your lifts are going up and you’re getting faster, you can be more confident that you’re gaining more muscle than fat.
Your Body Fat Percentage Has Decreased
The most accurate way to tell if you’ve gained muscle is to get your body fat percentage tested. You can do this by getting a DEXA scan or taking a hydrostatic body fat test (where you’re submerged in water while sitting on a scale).
If the results from these tests show that your body fat percentage has decreased, but your lean mass percentage has gone up, it’s a strong indicator that you’ve gained muscle and lost fat.
The body fat testing methods above usually require appointments at hospitals or other medical facilities and referrals from a physician. They can also be expensive, and insurance doesn’t always cover them.
To track your body fat percentage at home instead, you can use calipers or a body fat scale. Calipers pinch your skin to measure its thickness. Body fat scales measure how quickly electrical currents travel through your body. The faster the currents, the more lean mass you have.
These methods aren’t as accurate, but you can still use them to gauge your progress. After getting a baseline number, recheck it every four weeks to see if it is going up or down.
Signs You’re Gaining Fat
You Don’t Have as Much Visible Muscle Definition
When you gain muscle, your muscles will pop more and feel harder. But if you gain more fat than muscle, you’ll look and feel “fluffy.” Your muscle definition won’t be as visible, and you may feel more bloated.
Your Body Fat Percentage Increases
As I mentioned earlier, some fat gain is inevitable when you gain muscle. But if you get your body fat tested and your body fat percentage has increased significantly while your muscle mass has stayed the same or gone down, you’ve clearly gained more fat than muscle.
Your Strength Has Plateaued or Decreased
In some cases, gaining fat can lead to decreased athletic performance. Based on a study from the University of Michigan, extra fat covering your muscles inhibits the muscles’ ability to move efficiently and generate power.
Higher body fat percentages are also linked to increased fatigue, which can make it harder to keep up with a consistent workout routine.
Your Clothes Are Tighter
An easy way to tell if you’re gaining fat is that your clothes no longer fit. If you find it more difficult to button your pants or notice that you have to fasten your belt on a looser hole, your weight gain is likely from fat.
It’s important to note, though, that your clothes may also fit differently if you’re gaining more muscle than fat. Shirts may feel tighter around the shoulders and biceps, and you may have to squeeze your legs and hips into your pants.
But if your clothes are tighter and you notice other signs such as feeling “softer,” chances are you’ve gained more fat than muscle.
Related Article: What To Do If You’re Gaining Muscle and Not Losing Fat
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What Is an Ideal Muscle to Fat Ratio?
The ideal muscle-to-fat ratio is about 70-90% muscle and 10-30% body fat. Where you should fall within these ranges depends on your gender, age, and athletic experience.
For example, women need higher body fat percentages because the extra fat gives them the energy to carry and nurse babies.
Similarly, the acceptable body fat ranges for older individuals are slightly higher due to the natural decreases in muscle mass (sarcopenia) that occur with age.
As well, many athletic individuals will naturally have lower body fat percentages due to the muscle mass they have as a result of their training.
The below tables show the classifications of body fat percentages for men and women according to the University of Pennsylvania.
Body Fat Percentage Classifications for Men
| Classification | Age 20-29 | Age 30-39 | Age 40-49 | Age 50-59 | Age 60+ |
|---|---|---|---|---|---|
| Too low | <8% | <8% | <8% | <8% | <8% |
| Excellent | 8.1 - 10.5% | 8.1 - 14.5% | 8.1 - 17.4% | 8.1 - 19.1% | 8.1 - 19.7% |
| Good | 10.6 - 14.8% | 14.6 - 18.2% | 17.5 - 20.6% | 19.2 - 22.1% | 19.8 - 22.6% |
| Average | 14.9 - 18.6% | 18.3 - 21.3% | 20.7 - 23.4% | 22.2 - 24.6% | 22.7 - 25.2% |
| Poor | 18.7 - 23.1% | 21.4 - 24.9% | 23.5 - 26.6% | 24.7 - 27.8% | 25.3 - 28.4% |
| Too High | >23.2% | >25% | >26.7 | >27.9% | >28.5% |
Body Fat Percentage Classifications for Women
| Classification | Age 20-29 | Age 30-39 | Age 40-49 | Age 50-59 | Age 60+ |
|---|---|---|---|---|---|
| Too low | <14% | <14% | <14% | <14% | <14% |
| Excellent | 14 - 16.5% | 14 - 17.4% | 14 - 19.8% | 14 - 22.5% | 14 - 23.2% |
| Good | 16.6 - 19.4% | 17.5 - 20.8% | 19.9 - 23.8% | 22.6 - 27% | 23.3 - 27.9% |
| Average | 19.5 - 22.7% | 20.9 - 24.6% | 23.9 - 27.6% | 27.1 - 30.4% | 28 - 31.3% |
| Poor | 22.8 - 27.1% | 24.7 - 29.1% | 27.7 - 31.9% | 30.5 - 34.5% | 31.4 - 35.4% |
| Too High | >27.2% | >29.2% | >32% | >34.6% | >35.5% |
Frequently Asked Questions
Are Muscle and Fat the Same?
Muscle and fat are not the same. Muscle is contractile tissue. It drives our body movements and allows us to produce force and power. Fat is non-contractile. It provides energy but does not produce force. Muscle is also denser than fat, so one pound of muscle will take up less space than one pound of fat.
How Much Does a Pound of Muscle Weigh?
A pound of muscle weighs one pound. Many people mistakenly believe muscle weighs more than fat, but this is not true. One pound is one pound regardless of the object you’re weighing. However, muscle is denser than fat and takes up less space than an equal amount of fat.
Does Muscle Make You Heavier?
Having more muscle mass will make you heavier. However, it can also help you look leaner and have better muscle definition. While your scale weight may increase as you gain muscle, you may also lose inches and become stronger in the gym.
Need a workout routine that can help you build muscle, lose fat, and get stronger? Check out Fitbod. It automatically creates a routine based on your individual goals and makes adjustments as you log your training data so you can continuously progress. Download the Fitbod app today and try workouts for free!
About The Author
Amanda Dvorak is a freelance writer and powerlifting enthusiast. Amanda played softball for 12 years and discovered her passion for fitness when she was in college. It wasn’t until she started CrossFit in 2015 that she became interested in powerlifting and realized how much she loves lifting heavy weights. In addition to powerlifting, Amanda also enjoys running and cycling.
