Building muscle and losing fat at the same time. Is that possible? If so, how can it work if you need a calorie surplus to build muscle and a calorie deficit to lose fat? That actually contradicts "at the same time", doesn't it?
Definition "At the same time"
Let's start from the beginning: "At the same time" means to build muscle and lose fat while being on maintenance calories. We'll get to whether that's possible in a moment by looking at the theory behind it and, of course, the practice. However, let's define "maintenance calories" first.
Most people think a constant body weight on a weekly or monthly basis means that we have been on maintenance calories. However, this is not correct. Maintenance calories only means that you take in as many kcal through food as you burn. This does not mean that your body weight has to remain constant. Even if it remains constant, it does not mean that you are on maintenance calories.
Sure, body weight can fluctuate due to temporary water fluctuations. However, we're not talking about that now. These fluctuations even out over several weeks or months anyway. We are talking about a change in body weight due to a changing ratio of muscle to fat mass.
Maintenance calories doesn't mean your body weight has to stay constant - just that calorie intake = calorie expenditure.
Losing muscle and gaining fat at the same time
To illustrate this, imagine you have a refrigerator that weighs 100 kg including its contents. Now you take out 1 kg of fat-free steak and put in 1 kg of butter.
After that, the refrigerator still weighs 100 kg, but the stored energy in the refrigerator is completely different. The butter, which consists of fat, has much more energy than the steak, which consists mainly of protein. By putting the butter in and taking the steak out, you have significantly increased the energy storage of the refrigerator, even though the weight has remained the same.
Now imagine your body is this energy-storing refrigerator. 1 kg of body fat has about 7,700 kcal and 1 kg of muscle mass has about 1,800 kcal. Let's assume that you have caught a bad flu and have to lie in bed almost all day for 3 weeks.
During this time you will definitely lose some muscle mass. Let's say you lose 1 kg of muscle mass. So your energy storage is reduced by 1,800 kcal. If you eat in a way that you maintain your body weight during the flu, you will have gained 1 kg of fat (the compensation for the 1 kg muscle mass loss). The body fat increased your energy storage by 7,700 kcal. So, in total, you were in a net surplus of 5,900 kcal, WHILE your body weight remained constant.
This is an absolutely realistic example to show that a constant body weight is not a perfect indicator that you were on maintenance calories.
Building muscle and losing fat at the same time
The principle works similarly in the other direction as well. Let's say you start lifting weights and you do it for 3 months. Your body weight remains constant the entire time. As a beginner, you will certainly gain muscle mass during this time. Let's say you built 1 kg of muscle and lost 1 kg of fat. In that example, you weren't on maintenance calories either.
Required energy for building muscle
When it comes to building muscle, the calculation is a bit more complicated. Your body has to expend a relatively large amount of energy for the muscle-building process. Although 1 kg of muscle mass contains 1,800 kcal, your body must spend an additional 4,500 kcal to build this 1 kg of muscle mass. However, it is not yet known precisely how many kcal are required to build muscle.
If we assume this number is about accurate, around 6,300 kcal are required to build 1 kg of muscle mass. If you now build 1 kg of muscle and lose 1 kg of fat, you were in a net deficit of about 1400 kcal over the entire period, ALTHOUGH your body weight remained constant.
If you build 1 kg of muscle mass and lose 1 kg of body fat, you were in a deficit, even though your body weight remained constant.
Nevertheless, in many cases, a constant body weight is an indicator that you were on maintenance calories indeed – just not always.
First law of thermodynamics
So, as you've already noticed in the last example, there are definitely cases where you can build muscle and lose fat at the same time. Let's take a look at the theory behind this.
Fat and muscle gain require energy and fat and muscle loss release energy. So, for muscle gain you need to be in a calorie surplus and for fat loss you need to be in a calorie deficit.
Simultaneously in a calorie surplus and deficit
So, to build muscle and lose fat at the same time, you need to be in caloric surplus and deficit at the same time. This sounds unrealistic and is mostly the reason why many people don't believe that you can build muscle and lose fat at the same time. However, this is definitely not a paradox, because muscle and fat tissue must be considered separately.
These are 2 different systems. Your body distributes kcal to muscle and fat tissues independently. This effect is called "Nutrient partitioning" or "Calorie partitioning". So, for example, one tissue type can be in a calorie surplus and the other in a calorie deficit.
It is possible to build muscle and lose fat at the same time, as muscle and fat tissue are to be considered separately and can be in a caloric surplus or deficit independently of each other.
For example, if you are in a surplus of 100 kcal, then it is not mandatory that 50 kcal go into fat tissue and 50 kcal into muscle tissue. It can also be that 100 kcal go into muscle tissue and 0 kcal into fat tissue or the other way around. Or - and now it gets interesting - even 200 kcal can go into the muscle tissue. 100 kcal then come from the surplus through food and 100 kcal come from the fat tissue etc.
Calories from food vs. stored in the body
Yes, you have to be in a calorie surplus to build muscle. However, it does not necessarily have to come only from the kcal in food, but can also come from the kcal stored in the body. If you have 20 kg of body fat, you have 154,000 kcal stored in that body fat. You can use this "surplus" for building muscle, even if you eat exactly on maintenance (so no more surplus comes in through food).
This is the reason people with more body fat lose less muscle mass during a diet. They have much more energy stored in their body that can be used. With 20 kg of body fat, you have 154,000 kcal stored in your body, and with only 5 kg of body fat, you have only 38,500 kcal stored. This is a big difference.
Yes, you must be in a calorie surplus to build muscle. However, this does not necessarily have to only come from the kcal in food. It can also come from the energy stored in your body.
Just a little confusing info on the side: If you add the kcal stored in your body to the kcal you consume through food, then you can never be in a deficit - even with the most extreme crash diet. Your kcal needs are always covered by the food and the energy stored in the body.
But sure... if we talk about "calorie deficit", we usually mean that you take in less calories from food than you currently expend. This is how we continue to define deficit/surplus/maintenance - always in terms of calories from food.
That's enough on theory. What does reality show us? Is simultaneous muscle gain and fat loss observed often? Yes! There are countless studies showing this. Before you ask, yes, there are also a lot of studies showing it's even possible in advanced lifters.
A very recent literature review by Barakat et al. (2020) summarizes the results of all these studies. By the way, this literature review does not only show that you can build muscle and lose fat at the same time even as an advanced athlete, it also shows that other factors such as smart and hard training and sleep are much more important than determining the exact amount of calorie intake.
Building muscle and losing fat at the same time is possible even for advanced athletes!
Smart and hard training
And here we are at a very important topic that gets far too little attention from many lifters: Smart and hard training! Without a strong training stimulus, it doesn't matter what or how much you eat. Muscle mass is only built when your body experiences the need to do so. It only experiences this during smart and hard strength training.
With the Alpha Progression app you can plan, track and analyze your training to create a strong stimulus to build muscle and lose fat at the same time.
Another important point is the placebo effect. If you want to diet moderately in the next few months and it's already clear to you that you won't be able to build muscle during this time anyway, guess what happens then? That's right, you actually won't build muscle, because you consciously or unconsciously put less effort into your workouts. That's a self-fulfilling prophecy.
However, after reading this article, hopefully, you know that there is no justification at all for this thinking. You can build muscle and lose fat at the same time - even in a non-excessive deficit. Of course, this becomes more difficult when you are very advanced, but it is possible.
Shouldn't you be doing any targeted phases of being either in a calorie surplus or deficit at all right now? Not necessarily. Such phases allow you to focus more on one thing. If you want to build muscle faster (and accept some body fat), then go ahead and do a muscle building phase. If you want to lose body fat faster (and accept less muscle gain), then eat in deficit for a while.
However, if you are reasonably happy with your body fat percentage and don't feel like going through these intentional surplus and deficit phases, then don't feel guilty and eat roughly on maintenance. Rather concentrate on the most important thing: Smart and hard training for a long time.
If you want to optimize not only your nutrition but also your training, download the Alpha Progression app to track your workouts or let the app create a custom training plan designed for optimal muscle growth.