It’s the age-old fitness question: can you build muscle and lose fat at the same time?

Here at My Vital Metrics, one of the first things we will do when you come in for a fitness assessment depending on your results, will be to help you set a primary goal. For body composition clients this will often mean choosing between fat loss and muscle gain.

So, does that actually mean you can’t build muscle and lose weight simultaneously? Classic body-building would say so, claiming that you need to ‘eat big to get big’. Overall, it’s technically true that you need to be in a caloric surplus to gain muscle, and you most definitely need to be in a caloric deficit to lose fat – so that makes these two goals incompatible, right?

As always, body recomposition is a little more complex than that, so let’s break it down and see whether this Holy Grail of body recomposition is possible.

Before we dive into the topic of fat loss vs. muscle gain, we should point out that there are many other worthwhile health and fitness goals: movement quality; injury prevention; posture; sporting performance, and many more. With that in mind, let’s start with the phenomenon that causes the most confusion on the issue of whether you can gain muscle and lose fat at the same time: “newbie gains”.

Building Muscle and Losing Fat: “Newbie Gains”

There’s plenty of good evidence in the literature that for new lifters, gaining muscle and losing fat at the same time is absolutely possible. There is some debate however over the specific mechanism of action by which this is achieved. One theory is that because they are not yet efficient at converting food into muscle, the metabolic adaptations happening for the first time require a lot of extra energy from the body, and so someone burns extra fat.

However, most newbie lifter plans (if taking a newbie in an untrained state, and assuming they want to burn fat also) would usually put them into a caloric deficit, and so really the question is ‘how does a newbie gain muscle so well, when in a deficit?’ We’ll hold this question for a moment while we go through the science.

The Science of Losing Fat: A Calorie Deficit

The most important thing to remember is that you need to be in a caloric deficit to lose fat. This means you need to be eating less than your body burns to keep itself alive and you moving around. Everything you do, from breathing, or your heart beating, to brain function, even to the act of eating and processing food will expend calories. And, of course, your activity: moving around, and exercise is all part of that. How much less you need to be eating depends on a lot of factors.

The best way to establish an accurate sense of your caloric needs is through an RMR test. This will tell you how many calories you need each day to keep yourself alive (this is your Resting Metabolic Rate or Basal Metabolic Rate), and how many calories your Total Daily Energy Expenditure (TDEE) is. This is the number of calories you could eat to be in perfect energy balance – neither gaining nor losing weight. From there, we can work out how many calories you need to eat to lose fat. This will be somewhere between your TDEE and your RMR.

We have to remember, however, that being in a caloric deficit isn’t a magical switch to start burning fat alone – the body will make economies to try to balance its energy from all its systems and all its tissues. Without other stimuli to the body, the body is just as likely (more likely actually) to rid you of muscle which you aren’t using, because muscle is costly tissue to maintain. It may also leach from bones, and temporarily reduce expenditure in many other ways to balance its energy needs. This whole process: the process of removing tissue to use for energy is called ‘catabolism’, and someone in this state can be referred to as ‘catabolic’. So a deficit will (without other stimuli) lose us muscle – that’s the key thing to remember as we move to talk about how a caloric surplus works.

The Science of Gaining Muscle: A Calorie Surplus

Contrary to the above, to gain muscle you need to be in a caloric surplus. This means you need to be eating more calories than your TDEE. Of course, just eating more than you need is not sufficient to gain muscle. You need to send stimuli to the body to tell it where to put those extra calories. Left to its own devices, and without this stimulus, the body will add to systems as it sees fit. This might mean it upregulates (turns up the dial on) the immune system, hair and nail growth, mental energy, dopamine responses, and of course, there’s inevitably going to be some of those calories which go to fat stores, energy stored for future use. To predispose you to gaining muscle you have to have a good-quality hypertrophy or strength training plan. This creates the stimuli to the body to divert some of these excess calories over to muscle growth. It is a signal to say to the body ‘Hey, I am lifting big, so you’d better make these muscles stronger and bigger or I might injure myself or be unable to do what I need to do to get food and keep myself alive’. Of course, we know that your lifting is not directly connected to your survival, but from an evolutionary point of view, that’s how the body sees it. Likewise with the deficit though, a surplus will add to all tissues. If you weight-train, then some of that excess will go to muscle, and bone, as well as strengthening tendons and ligaments. Inevitably, however, some fat will also be gained, so sizing up the amount of the surplus is important. In classic bodybuilding methods, a surplus is the ‘bulking’ phase of the diet, and they accept that fat will be gained during the process, but they value muscle more so they take this hit, with the expectation that they’ll lose the fat later down the line. This whole process – the adding of energy to muscles, bones and other tissues is called ‘anabolism’ – so someone in this state is referred to as ‘anabolic’. You may recognise the term from ‘anabolic steroid’ – which are basically hormones which increase the body’s anabolism.

Energy Balance Throughout the Day

We haven’t discussed so far the important role of protein in the above processes. Suffice it to say that protein is critical as it contains all the building blocks that allow us to put on or keep muscle. The protein content of a diet is incredibly important in that it facilitates greater anabolism, and prevents excess muscle catabolism.

So from the above, it seems pretty clear – you are either anabolic or catabolic at any given point in time. Case closed, you can only pursue one goal at a time – right? Not quite.

So, the premise is correct: you can only be in either an anabolic state or a catabolic state at any one time, however, which state you are in will vary throughout the day. Just woke up and started moving about, before breakfast? You’re catabolic. Had a nice big breakfast, you’re now anabolic for a while. Just finished your workout? You’re very catabolic. Downed a protein shake? You’re anabolic again.

So you aren’t permanently in one state or another, but rather it varies throughout the day, and by playing with this, and timing your meals (and protein especially) appropriately, we might be able to get to this goal.

How to Fuel your Body to Build Muscle and Lose Fat

If you want to gain muscle and lose fat concurrently, you need to make sure that you’re in a surplus (eating more than you need) for some of your day, but also be in a deficit (eating less than you need) for the other parts.

When you are in each state will need to depend on your workouts. Remember, the major stimulus you can put into the system is a solid weight-training workout. So it is immediately after this, and for a few hours that you’ll want to be in a surplus so that the body diverts all those excess resources over to refilling muscle glycogen, and repairing muscle tissue. For the rest of the time you’ll want to be in a deficit.

Overall, the energy balance does need to be a deficit. If the balance at the end of the day or week is positive calories, then you will not be able to lose any fat.

Have we found the Holy Grail of body recomposition?

In short, both of these can happen at the same time, but it’s not the easiest balance to maintain for many people. Remember also that by aiming for both, you are compromising on maximal progress on each. We are all for this approach, however. It gets people eating a good amount of calories that is sustainable and should feel pretty filling, and good, and it allows people to pursue an overall better physique and get healthier on multiple measures of fitness simultaneously. We’d overall rather see this approach which may take a year or maybe even two, rather than the dramatic bulk-cut cycles we sometimes see.

That said, this approach may have diminishing returns the further up the bell curve you are in terms of existing muscle mass. In other words, if you are a person who is already carrying a lot of muscle from many years of training, managing to grow more muscle while in a deficit is increasingly unlikely the more muscle you already have. Going back to our ‘newbie gains’ discussion, this is probably why new lifters are so much better able to add muscle when in a deficit. If they are carrying much less muscle than we are evolutionarily capable of, the body is far more likely to add muscle as a priority given the right stimulus.

To find out more about how you can meet your body recomposition goals, book a free fitness consultation at My Vital Metrics today!

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