Can You Build Muscle In a Calorie Deficit / Lose Fat In a Surplus? (Science Explained)

It's a common fitness mantra: "You can't build muscle unless you're in a caloric surplus." While this holds true in many cases, it's not a universal rule. Like most things in fitness, the reality is more nuanced.

Introduction:

Building Muscle: Calories Aren't the Only Story

It's a common belief in the fitness world: you must eat more calories than you burn to build muscle. While a caloric surplus can support muscle growth, it's not the sole factor. Let's explore this with an example:

Imagine a well-trained individual who maintains their weight at 2,500 calories and has never specifically trained their biceps . They begin a 12-week cutting phase, reducing their calorie intake to 2,000 calories (a 20% deficit).

The Question: If they start dedicated forearm training with 20 sets per week during this cutting phase, will they gain significant forearm muscle?

The Answer: Yes, they likely will.

Why?

Unless this individual has an unusual response to training or is severely protein-deficient, they should still experience muscle growth in their forearms. This highlights an important concept:

As an example from the research, let’s look at one 2016 study at aStu Phillip’s Lab.In the following graph, you can see that on average, subjects lost about five kilograms of fat mass while gaining about a kilogram of lean mass.

Take note that this was despite being in acaloric deficitand due to the fact that they were on aprogressive resistance training programandeating a high-protein diet.

Not everyone can expect amazing body recomposition as depicted here. As I outlined in my science-explained YouTube video last year on this, the likelihood of any given individual actually building muscle in a caloric deficit depends on several factors.

It’s easier to build muscle in a caloric deficit if you:

1. Are a beginner - The less training experience you have, the easier it will be to build muscle in a deficit

2. Have a higher starting body fat percentage - Thehigher your starting body fat percentage, the easier it’ll be because the stored fat can serve as a massive energy source throughout the deficit.

3. Don’t crash diet - The smaller the deficit, the better (keep below ~20%)

4. Eat a higher protein diet - Keep proteinsomewhere around 0.8-1 g/lb bodyweight

If you want to make this a reality for you, keep those four factors in mind.

Next, let’s move along to what I consider an even more interesting question:Is it possible to eat in a caloric surplus and still lose body fat?

Once again, let’s just look at the math here. If you were to gain six kilograms of muscle, which is definitely possible over a year as a beginner or an early intermediate, while at the same time losing a kilogram of fat, then by definition you would have had to have a net surplus of 1,400 calories while losing body fat.

It’s important to note that again, that’s a total cumulative caloric surplus. So, if the transformation happened over a year or 365 days, that would actually only be about a four-calorie surplus per day, which is obviously not practical at all.

Because of the differences in energy density between fat and muscle, I think what this ultimately proves is that it’spossible to lose fat while in a caloric surplusif you build a lot of muscle very quickly.

At risk of just confusing things more, I’ll use two examples of differing lifting experience to prove the broader point that body recomposition certainly is possible, and actually expected, under certain circumstances. Because ofdifferences in the energy density of different body tissues,energy balanceandbody weightchangesaren’t always inextricably linked.

People in their first or second years of trainingcan expect to build muscle and lose fat at the same time, as long as their training program is set up properly, they’re eating sufficient protein, and the caloric deficit isn’t too large.

In practice, I’d recommend about a15-20 percent deficit. Generally, it’s best to focus oncompound movementsin the 6-15 rep range withprogressive strength increases from week to week, or month to month.

For people beyond their first couple years of training, despite the fact that some data does suggest that body recomposition is still possible in more experienced trainees, I still generally recommenddiscrete cutting and bulking cycles.This seems prudent because after a certain training age, trying to build muscle while in a caloric deficit will most likely result invery quickly diminishing returns. That is, you’ll either most likely get slower gains or as you get even more advanced, you could just be totally spinning your wheels and not really getting much of anywhere with either goal.

Before we end, I’m going to pose the first scenario once again.

We’ve got the same person in the same20 percent caloric deficit, but this time he’s been training his forearms with20 sets per weekfor the last five yearsleading into his cut. Throughout his cut,will he continue to build muscle in his forearms or will he at best maintain that muscle?