How do you know if you are losing fat or muscle?

January 10th 2019

As I strive to build more muscle with my strength workouts, I often wondered, how do I know if I am losing fat or muscle?


If you are wondering if you are losing fat or muscle, you need to take a macroscopic view of your entire lifestyle. If you are weight training, eating a healthy diet, getting a good night rest every day, and maintaining or even improving your strength, you can be sure that you are losing a lot of fat. You just need to be patient and continue executing your game plan, one day at a time. If, however, you find your strength decreasing drastically, you are eating a poor diet and you are not sleeping enough, you can guarantee that you are losing muscle mass.


Having a balanced diet is one key component of making sure that you are losing fat and not muscle. In order to maintain or even gain a bit of muscle during your weight loss endeavor, you need to supply your body with enough protein. The protein contains essential amino acids that help rebuild damaged muscles. In addition to maintaining an adequate source of protein, keeping your body healthy also involves eating enough carbohydrates, fats, minerals and other micronutrients.


Exercise is another key component to making sure you lose fat instead of muscle. One of the biggest contributors to muscle loss is inactivity. This is one reason why strength training is highly recommended for individuals looking to lose fat. If you do not use your muscles, you will lose them.


Proper recovery is a big component of losing fat instead of muscle. Making sure you get proper rest is crucial for your body to maintain and rebuild your muscle. This is one reason why doing too much cardio is detrimental for your weight loss journey - your body has no time to rest and your body, as a result, will waste away your muscle. So, make sure you balance your training and get enough sleep.


Getting enough sleep is vital for weight loss. If you are not sleeping enough, this throws off your hormone balance in your body. Cortisol is elevated, which increases the chances of your body to store more fat and to slow down muscle growth. By now, I am confident that you can tell the difference between a good night’s rest and a bad night’s rest. It is literally night and day.

Signs of losing muscle mass

As we come into the 21st century, weight issues are becoming more prevalent. When we have goals to lose weight, we want to make sure we are losing fat and not muscle. I also wondered how people track muscle loss vs fat loss so I decided to do some research. Here are some warning signs to look out for to warn you that you are losing muscle.

Strength loss

This is an easy sign to spot. If you find yourself losing strength in the gym, you can be sure that your body is losing muscle. While it is common to lose some strength while losing weight, be cautious about any drastic strength loss as they could be a sign that something is wrong.

Physique decline

Visually, a decrease in muscle tone is a sure-tell sign that your body is losing muscle. If you had worked hard to earn a chiseled body but you let yourself go a little, you could expect to lose some muscle definition.

Drastic weight loss

Weight loss, if your goal is to lose fat, is good. But losing too much weight too soon is a big warning sign. Your body can only lose a certain amount of fat at a time before it decides to start losing muscle as well. Keep a close monitor on your exercise routine, which should involve weight training and cardio, and your diet, which include an ample amount of protein, carbohydrates, and fats.


For overweight individuals, losing ½ pound to 1 pound a week is a reasonable goal if you are committed to keeping the weight off for good. If you are obese, losing 1lb a week is reasonable. 2lbs a week might be a bit aggressive but it really depends on the individual’s circumstances. It is easy to lose track of your goals as we are often tempted by short term satisfaction.

Feeling too tired all the time

This is a very subjective feeling. If you are losing weight, do expect to feel some sort of lethargic feeling as you are putting your body in a state to lose weight. This is very uncomfortable and your body will have various reactions to try and adapt to these changes. You may find that your body will adjust to your new habits, exchanging your bad habits for healthier ones in the process. However, if you find yourself consistently tired and even regressing in your exercise program, it is a big red flag that you are losing muscle mass instead of fat.

How do you know if you are burning fat?

Losing a healthy amount of weight

If you are following your weight loss program correctly, you should be steadily losing weight. Of course, there are times where you may see odd readings. Weight loss is not linear but over time, you should see your weight trending downward in a healthy way.

Losing inches off your waist

This is not a sudden change, but over time you will find that your clothes start to fit more loosely on your body. In both men and women, we tend to store fat in your waist. So, a pretty good indicator of fat loss is if we are losing inches from our waist.

Improved conditioning and performance

At first, it will suck. You may feel tired all the time. But after adjusting to losing some fat, you will notice that your conditioning and performance in the gym improve. You will feel as if you have more energy for more activities in your day.

Improvement of overall health

As you lose fat, you will see improvements in your health. Lower blood pressure, fewer sicknesses, and healthy hormone levels are all to be expected as you lose more fat.

Reduced cravings and hunger

Once you break the old, bad habits of excess eating, you will find that you are no longer craving sweets. You no longer need to eat as much. This is a result of your body adapting to the good habits you trained it to obey.

Other people started noticing

One of the best ways to realize that you are losing fat is that other people are noticing. Friends, families, your significant other, co-workers, they can tell. It may first appear in your face, as you continuously lose weight. In your gym, strangers may approach you and compliment your new physique. The compounding effects of burning fat are real and should be aspired for.

Losing muscle and gaining fat?

There are many ways your body can signal itself to lose muscle and to gain fat. Not eating a proper diet, filled with enough protein, carbohydrates, and fats is a guaranteed way to make a bad decision. Without nutrients to supply your body, your body will be forced to break down muscle since it is harder to maintain it.


Not lifting weights, doing too much cardio or a combination of both is also another way you can lose muscle. If you do not use your muscles in the appropriate way, they will atrophy. If you do not give your muscles time to recover and rebuild, it will atrophy.


Another way that you can lose muscle and gain fat is by being too aggressive with your calorie cut. For example, if you typically eat 3000 calories to maintain your body weight, it would be outrageous to decide on eating only 1500 calories for the next 6 months because you want to lose weight. Not only are you essentially cutting what you eat in half, but you may be putting your body into stravation mode, where your body is forced to use both muscle and fat as energy. Our bodies have an absolute minimum calorie count we must eat daily in order to function normally; its the minimum amount of calories we need to ingest in order to stay alive. So, while it may look good on paper to cut a lot of calories all at once, it does not work well in practice.

Is losing muscle mass bad?

It really depends on your goals and life circumstances. If your goal is to lose fat, losing muscle mass would not be great. On the other hand, if you were involved in an accident or needed to do surgery that would put you inactive for a few weeks, losing some muscle mass might not be the end of the world.


I had two instances in my life where I lost over 20lbs over a period of time. One was when I was involved in a car accident - I lost 20 lbs in about 3 months. The other was when I was just started working at my new corporate job. I lost 18 lbs in about 11 months. What is my point of telling you these personal stories? There are a time and place to lose muscle. If you are trying to lose excess fat, losing muscle might not be an ideal goal for you and you should try to minimize muscle loss. If, on the other hand, you had external situations where losing some weight is actually beneficial for your long term health and progression, then I would invite you to do so.

When you lose weight, do you lose muscle?

If you are consistently going to the gym to lift weights, eat a healthy diet and get adequate sleep, your muscle loss will be minimal. Yes, it may happen but it will be so minor that it is pointless to be stressed about it.


If you are not exercising, sleeping poorly and just restricting your caloric intake, you are losing muscle and fat. How much muscle? It depends on a lot of factors, like your genetics, training history, your bad habits, etc.


In order to maintain permanent weight loss, it should be gradual. Any aggressive tactics to lose weight are dangerous since they are not likely to be maintained over a long period of time. Longevity and patience are key to having a successful weight loss journey.

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