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How to Lose Fat and Gain Muscle at the Same Time

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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?” and want to know the perfect macros to lose fat and gain muscle at the same time.

We’re here today to answer these questions.

The short answer:

  • There are some individuals who can build muscle and lose fat at the same time. We will outline each group below.
  • But for most individuals, it’s challenging to build muscle and lose fat simultaneously.
  • Overall, for most people, it is not the strategy we recommend. Chances are high you’ll end up spinning your wheels and making minimal progress toward either goal (muscle gain or fat loss).

Now we’ll explain why this is true. 

What is Body Recomposition?

“Body Recomposition'' takes place when there is any change to the composition (aka, ratio of fat to muscle) of your 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 kind of tissue. Muscle and fat are two different functional ‘compartments’. 

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

So, we need to 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 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:

In order to lose weight, we must be in a caloric deficit (consuming fewer calories than we burn). In order to gain weight, we must be in a caloric surplus (consuming more calories than we burn).

To build muscle or fat cells, your body needs energy.

Your body will release energy when it breaks these cells down.

But the question is, once consumed, where do calories go — to muscle or fat tissue?

And when we burn calories (and energy leaves the body), will our body pull from our muscle or fat tissue?

This is the issue of ‘calorie partitioning’ and it’s an important precursor to understanding whether (and how) we could build muscle and lose fat at the same time. 

The truth is: we can’t control where our calories go (fat or muscle) when we eat more or fewer of them.

In an ideal world, we’d want all our calories to go into muscle tissue and none into body fat, right? 

And it would also be convenient if, when dieting, 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 a physiologist and author Lyle McDonald explains, that’s simply not reality.

How Calorie Partitioning Actually Works

When talking about how calorie partitioning really works, researchers refer to something called the P-ratio [1]. 

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

Most of the P-ratio is outside our direct control (mostly genetic). McDonald says we can control around 15-20% of it with how we eat or train [1].

Hormones are very important 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 the 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]

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

That’s theoretically possible, but it’s unlikely for most individuals.

(It’s also important to acknowledge that just because something is possible doesn’t mean it’s the ideal method or strategy. More on that below.)

Who Can Build Muscle & Lose Fat Simultaneously?

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

But hang on, there are three groups of people who 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:

1. Beginners in the gym with a higher body fat percentage

Individuals who are 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 have the effect of improving 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 are what lead to simultaneous muscle gain and body fat loss in these individuals. The transformations of these individuals can be quite impressive — it appears as if the body takes calories out of fat cells and uses them to build muscle.

It’s important 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 who is new to strength training but quite 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 level of body fat is the “sweet spot”. 

2. Athletes returning from time off

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

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

3. People using steroids

We aren’t going to spend a lot of time discussing this category, but you get the idea. Steroids essentially “override” normal physiology.

If I don’t fall under those categories, can I lose fat and gain muscle simultaneously?

The answer: maybe. But, as mentioned above, the risk is that you’ll end up “spinning your wheels” and making minimal progress in either direction.

The leaner and more muscular you are, the less likely you are to successfully lose fat and gain muscle at the same time.

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

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?!). 

How to Lose Fat and Gain Muscle

“Should I build muscle or lose fat first?”

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

If you’d like to learn more about how to effectively lose fat, 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 slowly add more calories and put on muscle. 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 keeping an eye on body composition, measurements and performance.

Here are a few other things you can focus on.

Protein Intake for Fat Loss

Wondering what to eat to lose fat and gain muscle? 

Protein plays an extremely important role in muscle maintenance and 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. It 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 with the muscle recovery process after a tough workout [3]. 

When it comes to protein intake, the precise amount you need is best handled and monitored by a 1:1 coach who can prescribe an amount based on your body and training style. We also always recommend talking to a doctor before making any big changes to your diet. 

That being said, studies show that around .8-1g per pound of bodyweight is a good jumping-off place for most people - especially those who are 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 it stimulates muscle growth. This can help to offset potential muscle loss seen with lower-calorie diets.

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

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

As you can tell, losing fat and gaining muscle at the same time is nuanced and there are many moving pieces. 

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

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  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 https://bodyrecomposition.com/fat-loss/insulin-resistance-fat-loss
  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. 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
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Posted by Katie Holmes
Katie is a coach and the Content Coordinator for WAG. She was an attorney but realized her passion was in helping people transform their lives and become the happiest, healthiest versions of themselves.

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