Illustration showing a skinny guy bulking up and gaining muscle.

Do You Need to Bulk to Build Muscle?

“Bulking” is a term that carries some hefty baggage. For some, bulking is only way to build muscle. For others, it’s little more than a surefire way of getting fat. Not everyone needs to bulk to build muscle. Some people do, though.

That leaves us with a few questions:

  • Will a calorie surplus allow you to build muscle faster?
  • Can you lose fat and build muscle at the same time?
  • Does bulking cause needless fat gain?
  • Should skinny-fat guys bulk?
  • Should skinny guys bulk?
Cartoon illustration showing a skinny beginner bulking up and leanly building muscle.

What is Bulking?

There are a few different ways to define “bulking”. But let’s start with the basic definitions of bulking, cutting, and body recomposition, then work our way out from there.

  • Bulking: going into a calorie surplus (gaining weight) to facilitate muscle growth. What separates bulking from merely “gaining weight,” though, is bulking has an emphasis on gaining muscle while minimizing fat gain.
  • Cutting: going into a calorie deficit (losing weight) to make it faster and easier to lose fat. What separates cutting from simply “losing weight,” though, is cutting has an emphasis on losing weight while maintaining or gaining muscle.
  • Body recomposition: achieving both fat loss and muscle gain within a given period of time. When someone loses fat while bulking or gains muscle while cutting, they’ve achieved body recomposition. Still, when people talk about “recomps,” they’re usually talking about gaining muscle and losing fat while maintaining the same overall body weight.
  • Maintaining: is when you casually lift weights and eat a good diet without intentionally gaining muscle or losing fat. That’s great. Most strong, healthy people spend most of their lives maintaining their progress.

If we look at these definitions, they all consider body composition. Bulking is designed to help people build muscle without gaining fat. Cutting is designed to help people burn fat without losing muscle. Body recomposition is when you strive for both at the same time.

Is Bulking the Best Way to Build Muscle?

My Skinniness Forced Me to Bulk

So, first of all, I want to be open about my bias. I started off quite underweight. I was 6’2 and 130 pounds. I wanted to build muscle, become bigger, and bulk up to a lean 150 pounds. No amount of body recomposition could possibly take me from 130 up to 150 pounds. I needed to add extra mass to my frame. I had to bulk.

If I was a skinny-fat 150 pounds, I might have taken a different approach. I could have tried to burn off the fat and replace it with muscle, maintaining a similar body weight. But that wasn’t my plight.

And then, of course, once I hit 150 pounds, I realized I wanted to be 170 pounds. Then at 170 pounds, I realized I wanted to be 190 pounds. And then 200 pounds. That’s how, between 22 and 32 years old, I gained 70 pounds:

Before/after photo of Shane Duquette starting skinny, bulking up, and building muscle.

I gained all of my muscle size and strength during these focused periods of gaining weight. Over these past ten years, I’ve spent maybe two years bulking. During those two years, I made all of my progress. During the other eight years, I was lifting weights and eating a healthy diet, but didn’t gain much muscle. The reason for that is simple: I’m not overweight. So if I’m not gaining weight, how could I gain muscle?

Building Muscle in a Calorie Deficit (Cutting)

If you’re overweight or skinny-fat, you don’t need to bulk. You have extra energy around your stomach. You don’t necessarily need extra energy in your stomach. They have a surplus of body fat, and so their body won’t fight to keep it (study, study).

Graph showing body recomposition from cutting.

For example, this study found that most people who lifted weights, did some cardio, and ate in a calorie deficit could build muscle while losing fat. We see this in our members all the time. When people start off with extra fat to lose, they can often build muscle as they lose it.

A before and after photo showing Johnny's cutting results.

However, although it’s realistic to gain some muscle mass while cutting, it’s still slower and harder. Here’s why:

  • Eating fewer calories reduces muscle protein synthesis, even when protein intake is high. That makes it much harder to gain muscle mass. This study shows that a calorie deficit of 500 calories per day (losing about a pound per week) decreases muscle-protein synthesis by 20%.
  • Prolonged calorie deficits reduce testosterone production (study). Fluctuations within the normal testosterone range don’t always affect muscle growth or fat loss. Still, generally speaking, higher testosterone levels make it easier to improve body composition. Short periods of mild calorie deficits shouldn’t be much of a problem, but it’s certainly not ideal.
  • Eating fewer calories increases growth hormone production. When people eat in a calorie deficit, hypertrophy training causes their growth hormone levels to rise higher than normal (study). Growth hormone production also increases during fasting periods. That’s why intermittent fasting increases growth hormone production (study). However, despite its name, growth hormone has a fairly weak association with muscle growth (study).
  • Reduced activation of mTOR (study), which controls muscle growth and breakdown, controlling whether we gain or lose muscle. So when trying to build muscle, we want more mTor, not less.
  • Lowered immunity (study). Another side-effect of being in a prolonged calorie deficit, especially when already fairly lean, is that it can reduce our immunity. Exercise improves our immunity, but we still need to be more cautious with how hard we train.

Building Muscle at Maintenance (Body Recomposition)

Building muscle is easier when you aren’t in a calorie deficit. Everything runs more smoothly. Nothing is suppressed. You can build muscle by following a good hypertrophy training routine, eating a nutritious diet, getting enough sleep, and improving your lifestyle.

Graph showing that lifting weights, eating a good diet, and getting proper sleep causes body recomposition.

For example, this study found that participants who were given a workout, diet, and lifestyle program could gain muscle and lose fat while staying at the same body weight. In fact, if we look at overweight beginners, it’s unclear if there’s any benefit to eating in a calorie surplus. They build muscle perfectly well either way.

If you’re already under 15–20% body fat, you aren’t overweight, so you don’t have “extra” fat. Your body won’t necessarily want to lose what little you have. You might still be able to achieve body recomposition, but it will be a longer, slower, and more finicky process.

Before and after photo of a guy building muscle and losing fat simultaneously, achieving body recomposition.

But you can’t recomp forever. Eventually, you’ll run out of extra fat. One day, you’ll hit a plateau. That’s when it’s time to bulk.

Building Muscle in a Surplus (Bulking)

Most bodybuilders, powerlifters, and athletes go through periods of intentionally gaining weight. Bodybuilders call it their “offseason,” powerlifters call it a “massing phase,” and almost everyone else calls it “bulking.”

Bulking brings several physiological advantages:

  • Consuming a calorie surplus causes muscle growth (study, study). Most people who gain weight build around one pound of lean mass for every two pounds of fat they gain. This makes their body composition worse, of course. They become overweight. But they’re still gaining muscle—without lifting weights, eating a good diet, or living a healthy lifestyle.
  • A calorie surplus may increase testosterone, IGF-1, and insulin (study). Mind you, these small increases in anabolic hormones, while nice, may not lead to measurable amounts of extra muscle growth (study, study). It’s hard to say.
  • Eating more calories means eating more nutrients. More protein, carbs, healthy fats, fibre, vitamins, minerals, phytonutrients, and probiotics. Not only will you have more energy to invest in muscle growth, but you’ll also have more of everything.
Before and after photo showing the results of a skinny guy bulking up with the Bony to Beastly Program.

Numerous studies show rapid gains in lean muscle mass when participants eat in a calorie surplus, while those eating at maintenance barely gain anything.

Graph showing muscle growth and fat loss while bulking on a high-carb diet.

For instance, in this 8-week study, some participants were given a mass gainer shake, driving them into a calorie surplus. They gained 7.5 pounds of lean mass while losing 0.5 pounds of fat. The control group lifted weights but wasn’t told to increase their calorie intake. They failed to gain a significant amount of muscle mass.

Most studies show tremendous amounts of muscle growth from bulking. For instance, when we were researching whether keto was good for bulking, we came across this study:

The participants following the ketogenic diet couldn’t get into a calorie surplus, and so they struggled to build muscle, even though they were following a good bulking program. The high-carb group succeeded at eating enough calories, allowing them to gain three pounds of lean mass in eight weeks while losing a pound of fat.

Bulking Maximizes Muscle Growth

There’s an overwhelming amount of evidence showing faster rates of muscle growth while bulking. This study recommends a calorie surplus of at least 200–300 calories to maximize muscle growth. In this study, Eric Helms, PhD, and Brad Dieter, PhD, recommend a calorie surplus of at least 350–500 calories per day to maximize muscle growth.

Before and after photo showing the results of a skinny guy working out to build bigger arms and biceps.

The Three Most Common Types of Bulking

There are three common types of bulking. If you can understand the pros and cons of each, you can venture down the path that suits you best.

  • Dirty Bulking: a careless approach to bulking. It typically combines a strength training program with a “see-food diet,” where you eat whatever you want. Strength training isn’t optimized for building muscle. Neither is a see-food diet. It’s not a bad way to gain strength, but it’s not ideal and often causes a disproportionate amount of fat gain.
  • Lean Bulking: bulking with an emphasis on keeping your gains lean. This is done by following a good hypertrophy training program, eating a nutritious bulking diet, living a healthy lifestyle, and keeping the calorie surplus small. It usually involves tracking calories.
  • Aggressive Bulking: bulking with an emphasis on maximizing muscle growth. This involves rigorous hypertrophy training, eating a nutritious bulking diet, and living a healthy lifestyle. The larger calorie surplus allows for faster weight gain, supporting a faster rate of muscle growth.
Before and after photos showing Marco Walker-Ng building muscle as a skinny ectomorph.

I’ve tried all the different styles of bulking. My business partner, Marco (above), gained 63 pounds while getting his health sciences degree and strength coach certifications.

Before and after photo of a woman bulking up and gaining weight.

My roommates have bulked up. My little sister has bulked up. My wife has bulked up (above). And we’ve helped over 10,000 other skinny people bulk up. Nobody knows bulking better than we do.

Before and after photo of a skinny guy bulking up and becoming muscular.

Examples of Aggressive Bulking

Here’s one of our members, Eddi, who decided to bulk for his 60th birthday. He was quite thin, allowing him to bulk aggressively without gaining much fat, at least during the first few months, while making his newbie gains.

Here’s my own three-month bulking progress. Depending on how kind you are, you may be able to tell I was already an intermediate lifter with a successful bulk under my belt. I’d already bulked up from 130 to 150 pounds by this point. This shows me gaining another 25 pounds, bulking up to 175 pounds:

Before and after progress photos showing Shane Duquette bulking up.

Like Eddi, I chose to bulk aggressively. Over three months, I gained just under 25 pounds, putting my average weight gain at nearly two pounds per week. Now, my gains weren’t entirely lean. I’m not trying to say that I gained 25 pounds of muscle. But my fat gain was modest enough that it wasn’t that noticeable. Plus, I was still well within the healthy body-fat percentage range.

And I’m not an outlier, either. We have plenty of intermediate lifters who choose to do more aggressive bulks. For instance, here’s Johnny gaining over a pound per week for five months straight:

Before and after photo of an intermediate guy building muscle

What you’ll notice, though, is that in all of these cases, our members have a couple of things in common:

  • We’re starting quite lean, meaning that even if we gain a couple of body-fat percentage points, it doesn’t matter. Going from 11% to 14% body fat isn’t unhealthy, it doesn’t harm our appearance, and it barely even affects the appearance of our abs.
  • We’re still at least somewhat thin, meaning that we’re still relatively far away from our genetic muscular potential. With a good hypertrophy program, enough protein, a good diet, and clever healthy lifestyle changes, we can still build muscle rather fast without being limited by our genetics.

Examples of Lean Bulking

And that brings us to lean bulking. With lean bulks, we still do everything in our power to build muscle, but we slow down the rate of weight gain to reduce the risk of the surplus calories spilling over into fat gain. Here’s a good example:

Progress photos showing a skinny guy bulking up and becoming more muscular.

Mickey is gaining half a pound per week. That’s less than half as quickly as the more aggressive bulkers. But it’s still more than enough to gain 20 pounds in a single year, and with less likelihood of gaining a noticeable amount of fat. Is that better than aggressive bulking? Maybe. It depends on the person.

For another example, here’s Abousha. He had to bulk while travelling for work, making do with whatever food and equipment was available. To keep his gains lean under tougher circumstances, he bulked at a slower pace. It worked out great:

Before and after progress photos showing Abousha bulking up with the Bony to Beastly Program.


Most people can build muscle without bulking. They’re overweight. That extra fat is rich with energy that can be invested into muscle growth. This is called body recomposition. There’s no need to bulk until you’re healthfully lean and/or reach an insurmountable strength plateau.

Skinny guys do need to bulk to build muscle. If you’re thin, you don’t have extra energy. What little fat you have is being saved for emergencies. Your body won’t want to invest it into muscle growth. If you want to build muscle, you need to gain weight. You need to bulk.

Skinny-fat guys don’t need to bulk right away. You have some extra energy stored as body fat. If you’re new to lifting weights, eating a good diet, or living a healthy lifestyle, you should be able to build muscle while losing fat, at least for a while. You can think about bulking when you get down to a healthy body-fat percentage and/or struggle to progressively overload your big lifts.

Photo showing the Bony to Beastly Bulking Program for Skinny and Skinny-Fat Guys

Alright, that’s it for now. If you want more muscle-building information, we have a bulking newsletter for naturally skinny guys. If you want a full foundational bulking program, including a 5-month full-body workout routine, diet guide, recipe book, and online coaching, check out our Bony to Beastly Bulking Program. Or, if you want a customizable intermediate bulking program, check out our Outlift Program.

Shane Duquette is the founder of Outlift, Bony to Beastly, and Bony to Bombshell, each with millions of readers. He's gained seventy pounds and has over a decade of experience helping more than ten thousand naturally thin people build muscle. He also has a degree in design, but those are inversely correlated with muscle growth.

Marco Walker-Ng is the founder and strength coach of Outlift, Bony to Beastly, and Bony to Bombshell. He's a certified trainer (PTS) and nutrition coach (PN) with a Bachelor's degree in Health Sciences (BHSc) from the University of Ottawa. He has over 15 years of experience helping people gain muscle and strength, with clients including college, professional, and Olympic athletes.