Illustration showing a skinny guy who gained too much fat while bulking.

How Much Fat Will You Gain While Bulking?

One of the most common bulking mistakes is to be so scared of gaining fat you fail to gain weight. If you’re 130 pounds, the only way to get up to 180 pounds is to gain weight. There’s no other path there. You have to bulk.

But bulking is a dastardly process. You can just as easily mess it up by gaining too much weight, causing needless fat gain. You can cut the fat away, of course. It still works out in the end. But it can be a frustrating setback.

To make things even trickier, many factors affect the ratio of muscle and fat you gain, including your workout program, your bulking diet, your genetics, and even your sleep habits. It’s possible to bulk at a reasonable pace and still gain extra fat.

If you notice fat gain, does that mean you’re doing something wrong? If not, how much fat should you expect to gain while bulking?

Cartoon illustration showing a skinny beginner bulking up and leanly building muscle.

Focus on Gaining Muscle

The main purpose of bulking is to gain muscle size and strength. The secondary goal is to limit fat gain, but if some fat comes along for the ride, it’s not the end of the world. It’s fairly easy to get rid of any fat you gain, especially if you’re naturally thin, and especially if there isn’t that much of it.

Most skinny guys have the opposite problem. They’re so nervous about gaining fat that they fail to eat enough calories, preventing muscle growth. If you’re like me, starting off at 130 pounds, then the best path forward is to do a bonafide bulk, focusing on gaining weight, getting stronger, and getting bigger.

Before and after photos showing Shane Duquette bulking up leanly.

If you notice a bit of fat gain, that’s okay. The trick is to ensure you aren’t gaining fat needlessly and never get so fat that it begins to harm your health (or appearance).

Before and after photo of a skinny guy leanly building muscle and bulking up in one year

For instance, Hugo spent a few months bulking up, focused on getting bigger and stronger. He gained a bit of fat while doing it, so he spent a couple of months cutting. By the end of the year, he was up 40 pounds and looked leaner than when he started. This is the power of bulking. It allows for fast muscle gain.

During my most disastrous dreamer bulk, I stupidly gained around 25 pounds of fat. But I also broke all of my personal strength records. That fat is long gone, and I still have the muscle I gained. The only real downside was needing to spend 3 months cutting. I don’t recommend that approach, but it’s nothing to be afraid of. Most skinny guys are able to burn fat quite easily.

If you’re gaining 0.25–1 pound per week, and if you’re gradually adding weight or reps to your big compound lifts, then your bulk is going well. You don’t need to stress. If you notice some fat gain, slow down, but keep going. Keep gaining weight and getting stronger.

Gaining Fat Doesn’t Mean Being Fat

Just because you’re gaining fat doesn’t mean you’ll become fat. If you’re a lean guy now, gaining another 5–10 pounds of fat won’t make you fat. You’ll still be lean. You’ll just be a little bit less lean. It will still look good and be healthy. There’s no real harm to it.

Before and after photo showing the results of a skinny guy bulking up with the Bony to Beastly Program.

For example, Dan bulked aggressively, gaining an impressive amount of muscle and strength, but also some fat. You can see both the muscle gains and fat gains quite clearly. The extra muscle looks great, and he’s still got a healthy amount of fat. There’s no real downside here.

The trouble is when people drive their body-fat percentage too high. If you start off skinny-fat and gain 20–30 pounds of fat, you’ll become overweight. You might not like how it looks. It may harm your health. So it’s best to stop bulking long before that happens.

How Fat is Too Fat?

A good rule of thumb is to stop bulking before your waist circumference swells to 36 inches. The NIH recommends keeping your waist circumference under 40 inches (study). The idea is to make sure we aren’t accumulating too much visceral fat around our organs. So we can play it extra safe, stopping a few inches shy of that.

Also, keep in mind that lifting weights, doing some cardio, eating a good bulking diet, and living a healthy lifestyle reduce the proportion of visceral fat we gain. A good bulking program not only gives us the health benefits of being stronger, fitter, and more muscular, it also helps ward off the harm of gaining fat. (More of the fat we gain is subcutaneous, which doesn’t have the same negative health implications, even if we gain a bit too much of it.)

Should You Cut Before Bulking?

If you’re overweight, you should start with a cut. Get rid of the extra fat first. If you follow a good workout and diet program, you’ll be able to build muscle even while you’re burning fat. Then, once you’re lean and healthy, you can gear into a slow, lean bulk.

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

If you’re skinny fat, you’ve got options. You aren’t overweight, so you don’t necessarily need to cut. You can if you want, but you don’t need to. Here’s our article about what to do if you’re skinny-fat.

If you’re relatively lean or thin, you don’t need to cut. Being healthfully lean is great. Being leaner than that doesn’t tend to help. There’s no need to cut down from 16% to 12% or anything like that. You’ll build muscle faster and more leanly if start bulking at your current body-fat percentage.

What Ratio of Muscle to Fat Should You Gain?

Most overweight beginners can gain muscle while losing fat. When they start lifting weights, they can dip into their fat reserves, using that energy to convert the protein they’re eating into muscle mass.

Skinny guys can’t build a significant amount of muscle without gaining a significant amount of weight. And with that weight gain, there’s the risk of gaining fat. That’s the risk we take while bulking. Fortunately, many of us are naturally lean, allowing us to bulk quite leanly. Even if we do gain fat, we often have a fairly easy time getting rid of it.

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

You won’t necessarily gain fat while bulking. Even with bonafide bulks, there’s plenty of research showing totally lean gains. This 8-week study found that guys eating a good bulking diet while following a rigorous hypertrophy training routine were able to gain 7.5 pounds of muscle without gaining any fat. Some of our members get results like that, too.

GK's lean bulking results

But you’ll probably gain at least a little bit of fat. Most studies, even when a good diet is combined with a good workout program, find that most people gain at least a little bit of fat while bulking. This is especially true if you’re an intermediate lifter and you’ve already gotten your newbie gains.

There’s no specific ratio to aim for. It all depends on your genetics, your circumstances, and what you want. The trick is to make sure you’re bulking properly and getting results. Are you progressively overloading your lifts? Are your body-part measurements going up? Are you gaining weight at a reasonable pace? If you are, you’re doing good.

Study graph showing how much muscle and fat guys gain when bulking fast.

For example, in a study by Ribeiro and colleagues, the group gaining two pounds per week built twice as much muscle as the group gaining one pound. However, they also gained six times as much fat. Which group got better results? It all depends on what you want.


If you’re overweight or skinny fat, you can build muscle without gaining any fat at all. You can do that by either losing weight or keeping your weight stable. That isn’t bulking, though. When you switch to bulking, you may start gaining fat.

Most skinny beginners are able to bulk quite leanly. If you’re gaining 67–100% muscle, you’re doing great. If you’re gaining less than that, you might want to slow your bulk down.

When you’re an intermediate or advanced lifter, you might be willing to accept a lower proportion of muscle growth if it helps you get through strength plateaus. A 50–50 ratio of muscle and fat gain is perfectly fine. You might be able to do better. But even if you do worse, progress is still progress.

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 free bulking newsletter for skinny guysIf 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.

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