It’s one of the most frequently asked questions in health and fitness: How do I gain muscle and lose fat at the same time?

Some people phrase it differently, asking, “How do I replace fat with muscle?” or “can I gain muscle while losing fat?” and wonder how much to eat to lose fat and gain muscle.

We’re here today to answer these questions!

Can I Lose Fat and Gain Muscle?

Some lucky individuals can build muscle and lose fat at the same time. Beginners to a weight lifting program, athletes who have taken a substantial amount of time off or people with a lot of weight to lose are a few. We will outline and dive into each group in more detail.

Most people who “eat healthy” and “work out” regularly may struggle to build muscle and lose fat simultaneously. It doesn’t mean staying strong and dropping fat is impossible. It just means you need to focus on one goal at a time.

Chances are high you’ll end up spinning your wheels and make minimal progress toward either goal (muscle gain or fat loss) if you try to chase both goals simultaneously. 

So, how can you lose fat and gain muscle? To answer this question fully, we have to start by talking about body recomposition.



What is Body Recomposition?

“Body recomposition' occurs when there is a change to the ratio of fat to muscle in the body. When most people refer to “body recomposition,” they’re referring to dropping body fat and putting on lean muscle.

The human body isn’t one giant clump of the same tissue. Muscle and fat are two different functional ‘compartments.’

In other words, it is physiologically impossible to “replace” fat with muscle, or vice versa. 

The Law of Thermodynamics

Let’s start by considering the first law of thermodynamics - the conservation of energy. It’s a law of energy balance.

This law states that energy can neither be created nor destroyed. Energy has to go somewhere and doesn’t just disappear.

An energy (calorie) surplus will lead to storage. An energy deficit will result in energy leaving the body.

In nutrition terms, you may have heard this concept explained like this:

  1. To lose weight, you must be in a caloric deficit (consuming fewer calories than you burn). 
  2. You must be in a caloric surplus (consuming more calories than you burn) to gain weight.

To build muscle or fat cells, your body needs energy. Your body will release energy when it breaks these cells down.

What Happens After You Eat?

As your body breaks down food, where do those calories go — to muscle or fat tissue? And when you burn calories (and energy leaves the body), will your body pull from your muscle or fat tissue?

This is the issue of ‘calorie partitioning,’ and it’s an essential precursor to understanding whether (and how) you could build muscle and lose fat simultaneously. 

You can’t control where your calories go (fat or muscle) when you eat more or fewer of them.

If you could choose, you’d probably want all your calories to go to muscle tissue and none into body fat.

It would also be convenient if all calories used came from fat stores. That would make it pretty easy to lose fat and gain muscle at the same time.

But, as physiologist and author Lyle McDonald explains, that’s not reality. 



What is Calorie Partitioning 

When discussing how calorie partitioning works, researchers refer to the P-ratio [1]. 

This represents the amount of protein gained (or lost) during over (or under) feeding.

H4: How Does Calorie Partitioning Work?

Most of the P-ratio is outside our direct control (primarily genetic). McDonald says we can control around 15-20% of it by eating or training [1].

Hormones are essential in determining your P-ratio:

  • High testosterone levels tend to have positive partitioning effects (more muscle, less fat) [1]
  • Chronically high levels of cortisol have the opposite effect (less muscle, more fat) [1]

The tricky thing is that the P-ratio describes the overall effect on your whole body. It cannot predict partitioning (in other words, when you’re in a surplus, it cannot predict the percentage of your energy that will go toward creating muscle cells vs. fat cells) [1].

Theoretically, if your body had enough stimulus (i.e. strength training), protein, and water, it could pull energy from your fat cells to build muscle tissue. That would be the closest we could get to losing fat and gaining muscle simultaneously.

That’s theoretically possible, but it’s unlikely for most individuals. (It’s also important to acknowledge that just because something is possible, it isn’t the ideal method or strategy. More on that below.)

Who Can Build Muscle & Lose Fat At the Same Time?

The information above may have left you feeling a bit discouraged about your ability to gain muscle and lose fat simultaneously.

But hang on, three groups of people probably can achieve this feat!

Several factors will impact whether you can gain muscle and lose fat at the same time, including:

  • Training age (i.e. how long you have been strength training)
  • Current body composition
  • Genetics
  • Insulin sensitivity 
  • Hormone balance

Now, let’s dive deeper into each of the three groups.


How to Lose Weight At The Gym

Beginners in the gym with a higher body fat percentage tend to drop fat while gaining (or at least maintaining) muscle.

Individuals new to strength training have a high potential for relatively rapid muscle gain. And with a higher body fat percentage, their bodies have more energy to spare and put toward muscle gain.

There is also a chance that these individuals are insulin-resistant. Put simply, this means their fat cells “don’t want” more energy [2].

When these individuals strength train, it sends a powerful growth stimulus to their muscles. This will improve their insulin sensitivity and nutrient uptake within muscle cells [2].

At the same time, their fat cells will remain insulin-resistant. So, calories are more likely to go to muscle cells [2].

These functions lead to simultaneous muscle gain and body fat loss in these individuals. The transformations of these individuals can be pretty impressive — it appears as if the body takes calories out of fat cells and uses them to build muscle.

It’s essential to keep in mind, however, that this only works if both factors are present: the individual is a strength training beginner, and they carry a higher percentage of body fat.

Someone new to strength training but relatively lean doesn’t have enough fat to “shunt” to the muscle.

And the longer you have been strength training, the slower your rate of muscle gain will be.

That is why the combination of being new to strength training and carrying a higher body fat is the “sweet spot.”

Can Athletes Lose Fat and Gain Muscle?

Athletes who took time off (either by choice or due to injury, etc.) and lost muscle mass and gained body fat will have a relatively easy time rebuilding that mass (thanks to ‘satellite cells’ and the ‘muscle memory’ effect) [1]. 

They also tend to have training routines and schedules to help them stay consistent.

Otherwise, athletes may need to focus on one goal before turning to another. For example, a seasoned athlete may go through a calorie surplus to put on muscle and then cut weight while maintaining as much muscle as possible. More on that below!

Steroid Use and Muscle Gain

We don’t spend much time discussing this as it isn’t something we recommend, but you get the idea. Steroids essentially “override” normal physiology and make it much easier for someone to gain muscle while dropping fat.

How To Lose Fat and Gain Muscle

Since those are three smaller populations, you’re likely still wondering, “I don’t fall under those categories, can I lose fat and gain muscle simultaneously?”

The answer: maybe.

But you run the risk of “spinning your wheels” and making minimal progress in either direction. The leaner and more muscular you are, the less likely you are to lose fat and gain muscle at the same time successfully.

Put another way, the more “advanced” you are with your training and body composition, the slower “body recomposition” will likely take.

What tends to happen for many individuals is that neither their nutrition nor training program is optimized for fat loss or muscle gain. For example, they may keep their calories too low to support muscle growth — but too high for fat loss.

This could lead to no changes happening at all (and how frustrating would that be?!). So, what can you do about it?



Should I Build Muscle or Lose Fat First?

“Should I build muscle or lose fat first?”

For most individuals, we recommend breaking down your journey into specific phases - fat loss or muscle gain - and focusing on one at a time. This is likely to lead to quicker results. 

If you’d like to learn more about how to lose fat effectively, check out this article about what it really takes to get leaner and this one about how to ensure you lose fat without losing muscle mass.

Focused on gaining muscle? We’ve got an article about that too.

In most cases, you’ll need to focus on dropping fat first and then reverse dieting to add more calories and put on muscle slowly. This helps you “lean out” and then stay lean as you focus your training and nutrition on muscle gain.

Along the way, you’ll know if you’re gaining muscle or fat by monitoring body composition, measurements and performance.

Not sure which one to pick first? Find your answer! From there, here are a few other things you can focus on.


What to Eat To Lose Fat and Gain Muscle

Wondering what to eat to lose fat and gain muscle?

Protein and Muscle Gain

Protein plays an extremely important role in muscle maintenance. When you’re in a caloric deficit with the goal of fat loss, eating enough protein will give your body the best chance at holding onto muscle in the process. 

Protein also increases the likelihood that when your body is in need of energy, it won’t pull from muscle to get it. Eating adequate protein also helps muscle recovery after a tough workout [3]. 

How Much Protein Do I Need?

Regarding protein intake, the precise amount you need is best handled and monitored by an online nutrition coach who can prescribe an amount based on your body and training style. We also recommend talking to a doctor before making any significant changes to your diet. 

Studies show that around .8-1g per pound of body weight is an excellent jumping-off place for most people - especially resistance training [4]. From here, you’ll need to make sure your overall calories are at a level in line with your goals.

Resistance Training for Fat Loss

Resistance training can help you hold onto more muscle while dropping fat, as resistance training stimulates muscle growth. This can help offset potential muscle loss seen with lower-calorie diets.

Resistance training also has a high excess post-exercise oxygen consumption (EPOC) as a fat-burning bonus. This means that your metabolism may stay higher for longer after weightlifting, so you can burn more calories even after your workout.

When you gain/maintain muscle, it also increases your resting metabolic rate, or RMR, which means you burn more calories at rest.

As you can tell, losing fat and gaining muscle simultaneously is nuanced, with many moving pieces.

A 1:1 online nutrition coach will get to know you, your goals, and your training preferences to help you decide where to put your focus and how to work towards your body composition goals. Then, they’ll be able to track your progress with you and adjust your plan as your body changes.


  1. McDonald, L. (2003). The Ultimate Diet 2.0. Lyle McDonald Publishing.
  2. McDonald, L. (2020, April 22). Insulin Resistance and Fat Loss. Retrieved July 19, 2020, from
  3. Helms, E., PhD, Valdez, A., MS, & Morgan, A., BS. (n.d.). The Muscle & Strength Pyramid: Nutrition (2nd ed.). Retrieved July 10, 2020.
  4. Leidy, H. J., Clifton, P. M., Astrup, A., Wycherley, T. P., Westerterp-Plantenga, M. S., Luscombe-Marsh, N. D., Woods, S. C., & Mattes, R. D. (2015). The role of protein in weight loss and maintenance. Am J Clin Nutr. 101(6), 1320S-1329S. doi: 10.3945/ajcn.114.084038
  5. Leidy, H. J., Clifton, P. M., Astrup, A., Wycherley, T. P., Westerterp-Plantenga, M. S., Luscombe-Marsh, N. D., Woods, S. C., & Mattes, R. D. (2015). The role of protein in weight loss and maintenance. Am J Clin Nutr. 101(6), 1320S-1329S. doi: 10.3945/ajcn.114.084038
  6. Helms, E. R., Zinn, C., Rowlands, D. S., & Brown, S. R. (2014). A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. International Journal of Sport Nutrition and Exercise Metabolism,24(2), 127-138. doi:10.1123/ijsnem.2013-0054