Does Building Muscle Burn Fat? Here’s the Science

The case for building muscle to burn fat appears to be a simple one.

When you build lean muscle mass, the additional muscle requires additional energy to maintain it.

In turn, this raises your basal metabolic rate, or the number of calories your body burns while at rest. Paired with a good diet, this increased demand for calories can help with weight loss.

Case closed.

Or is it? I’m not so sure…

You probably know that muscle tissue is more metabolically active than fat, and that it helps you burn more calories during the day.

So, in theory at least, an increase in muscle mass means that more fat will be burned.

Unfortunately that’s only partially correct — and certainly not to the extent we once believed.

In fact, research shows that the resting metabolic rate of muscle is a lot lower than most people think – around 6 calories per pound.

I should also point out that fat is more than just lifeless tissue. It secretes proteins such as leptin and cytokines, which can affect your metabolism. Fat has a metabolic rate of around 2 calories per pound.

So if you were to drop a couple of pounds of fat and replace it with the same amount of muscle, your resting metabolic rate would rise by less than 10 calories per day. That’s not enough to have any kind of meaningful impact on weight loss.

The estimates of the resting metabolic rate of muscle I’ve just given do make one assumption — a constant rate of protein turnover.

However, weight training will accelerate protein turnover (which refers to an increase in the rate of protein synthesis and breakdown) in the hours and days after training.

In other words, while the metabolic rate of muscle at rest isn’t as high as some people think, the metabolic rate of muscle while it’s recovering means that people with more muscle mass are going to burn more calories in the post-exercise period.

The second problem is that you’d need to build a huge amount of muscle to have a significant impact on your metabolism.

To burn an extra 10,000 calories a month — enough to lose almost 3 pounds of fat – you’d need to gain more than 50 pounds of muscle.

That’s an awful lot of muscle growth. It’s much more than the average person is going to build over the course of their training lifetime.

In short, the idea of building muscle to burn fat is a flawed one.

But that doesn’t mean strength training is pointless if you’re trying to burn fat. Far from it. An effective strength training program is going to improve your body composition in a couple of important ways.

Firstly, weight training burns calories (and fat). Not just during your workout, but after it’s finished as well.

Let’s say you’re following a strength training program that involves compound exercises like squats, deadlifts, presses, rows, pulldowns/pull-ups and so on.

Depending on how long it lasts and how hard you’re working, a single bout of resistance training can burn upwards of several hundred calories, which contributes to the calorie deficit required to lose fat.

What’s more, that same bout of resistance training will set in motion a series of muscular adaptations requiring even more energy.

• Damaged muscle fibers need to be repaired.
• New muscle protein needs to be synthesised and laid down.
• Depleted glycogen stores need to be restocked.
• Connective tissue needs to be remodelled.
• Motor neuron pathways need to be forged.

All of these metabolic processes have an energy cost associated with them.

And the more rebuilding work that has to be done, the more calories are being burned after your workout is over.

Second, if you don’t do some form of resistance training while you’re dieting, a lot of the weight you lose will come from muscle as well as fat.

It’s also worth pointing out that the amount of weight you lose is a lot less important than where that lost weight comes from.

If you drop 10 pounds of fat while gaining 3 pounds of muscle, your weight on the scales will only have dropped by 7 pounds. But you’ll look 13 pounds different.

Body Recomposition

Body recomposition refers to the process of changing your physique by burning fat and building muscle simultaneously.

Fat mass is lost while lean mass (mainly in the form of muscle tissue) is gained.

While it is possible to gain muscle and lose fat at the same time, it’s highly unusual to do both at the same rate.

That is, you shouldn’t expect to replace every pound of fat lost with a pound of new muscle.

Muscle growth tends to happen a lot more slowly than fat loss. You might be able to drop a couple of pounds of fat in a week or so. But gaining the same amount of muscle can take several months.

Here are the three “golden rules” of body recomposition:

1. Make sure that your overall diet and workout routine put you in a calorie deficit. If you’re in a caloric surplus, you’re not going to lose any weight no matter how much cardio or strength training you do in the gym.
2. Eat plenty of protein. An adequate protein intake is important when it comes to gaining (or even just retaining) muscle while you lose fat.
3. Do some form of resistance training on a regular basis, training the major muscle groups twice a week.

How to Tell if You’re Losing Fat vs Muscle

Sometimes, it can be hard to tell if weight gain or weight loss is the result of losing (or gaining) muscle rather than fat.

How can you be sure you’re losing fat rather than muscle?

The honest answer is that you can’t. Not with any degree of accuracy anyway.

Bioelectrical impedance analysis, the technology used in body fat scales, is largely a waste of time. Skinfold calipers can be useful in some circumstances, but even they have their problems. Even high tech methods like DEXA and underwater weighing can’t be trusted.

Instead, I suggest keeping track of your waist size, your weight on the scales, and your performance in the gym.

Tracking weight, waist size and your performance in the gym is not a particularly accurate way to quantify actual changes in body composition. But it will tell you if you’re on the right track and moving in the right direction.

How Many Calories Does It Take To Build One Pound of Muscle?

Although estimates vary, the number of calories required to build one pound of muscle is around 2500-3000 calories.

To be clear, that number doesn’t include the energy required to stimulate hypertrophy (i.e. going to the gym and lifting weights).

Rather, it’s the energy cost associated with the rebuilding and remodelling work that occurs in the hours and days after that workout is over.

However, that doesn’t mean a pound of muscle contains 2500-3000 calories. If you were to break down a pound of muscle, the amount of protein, carbohydrate and fat (stored in the form of triglycerides in and around muscle fibers) would supply around 600 calories.

Does Muscle Weigh More than Fat?

One pound of fat and one pound of muscle weigh the same. However, muscle tissue is denser. So even though they weigh the same, muscle tissue takes up less space than fat.

On average, the density of fat tissue is 0.9 grams per milliliter, while the density of muscle tissue is 1.1 grams per milliliter.

Let’s say that you fill a bowl with fat and weigh it. You empty out the fat and fill the same bowl with muscle. Then you weigh it again. The bowl full of muscle will be heavier than the bowl containing fat.

Put differently, muscle is more compact than fat. If you were to lose 10 pounds of fat and replace it with 10 pounds of lean body mass, your total body weight (as well as your body mass index, or BMI for short) would stay the same but you’d take up less space.

Take two people with an identical height and weight, and the person with a higher body fat percentage will typically wear larger clothes.

Frequently Asked Questions