Dirty Bulk vs. Clean Bulk: What is the Best Muscle Building Diet?

By EMMIE SATRAZEMIS, RD, CSSD December 8, 2022

Clean bulking vs dirty bulking: which one is best for increasing muscle size and gaining some serious lbs this bulking season? To settle the debate once and for all, we put these two different bulking methods head to head to see which comes out on top.

Learn the difference between the two, the pros and cons of both methods and choose the best muscle-building diet for you.

Bulking Diets

Gaining mass, including healthy weight, requires a calorie surplus - usually in addition to higher protein intakes, adequate weight training, and recovery periods. And while eating more food may sound like a dream come true for many of us, it is difficult to just gain lean muscle without any additional body fat accumulation.

Diet certainly plays a role here. How much you eat and the type of food you eat overall can have an impact on the type of weight you end up gaining - fat vs. muscle. So how can you tip the odds of more muscle mass in your favor?

There are two main types of muscle-building diets - a clean bulk or also called lean bulking, and a dirty bulk. A dirty bulk typically involves eating a lot of extra calories from high-calorie foods, including junk foods, to promote quick weight gain. A clean bulk uses a more moderate increase in calories in addition to healthier food choices.

But which one is best for achieving optimal mass?

To help you decide the best way to gain weight, we've put these two muscle-building diets head to head. When analyzing each approach we looked at:

Rate of Muscle Growth

The more calories you eat, the more weight you can gain quickly - hence the desire to do a dirty bulk. But let's take a look at how fast muscle gain in particular can happen on either diet. Is there a limit to the speed at which you are able to support muscle growth?

One study looking at trained athletes and the rate of muscle gain included a nutrition-controlled group and an ad libitum group (1). The nutrition-controlled group followed a macro-controlled diet plan aimed to promote weight gain of 0.7% total body weight per week or roughly a 500-calorie increase per day. The diet included high protein (1.4 to 2 grams of protein per kg body weight) and less than 30% of calories from dietary fat and suggested 5 to 7 nutritious meals throughout the day. Post-workout nutrition was also included.

The ad libitum group did not receive any nutritional counseling and were asked to increase their intake on their own accord with the same weight gain goal of 0.7% body weight gain per week.

While protein intake remained similar in both groups, calorie intake was actually higher in the nutrition-controlled group and thus resulted in more weight gain - 0.4% body weight per week compared to 0.2%. And nearly 72% of total weight gain in the nutrition-controlled group was muscle mass.

While increased calories were a clear supporter of increased mass in this study, protein intake is also important to consider. Protein plays a crucial role in gaining lean tissue because amino acids are the building blocks of all muscle - and without adequate protein, muscle gain is difficult to achieve.

This was evidenced in another small study where participants were fed an extra 1,000 calories a day to promote weight gain, with varying amounts of protein at either 5%, 15%, or 25% of their calories (2). All of the protein groups gained weight, but the low-protein group gained significantly less.

The Winner

What we can take away from the science here is that more calories equate to more weight gain faster - it takes roughly 2,800 additional calories to build one pound of muscle. And because a dirty bulk is often associated with higher calories, with adequate protein included, muscle mass may be achieved more quickly on this type of diet.

However, this approach may require some nutritional intervention, whether it is tracking calories or a systematized diet, since achieving higher calorie and protein goals can be difficult through ad libitum diets. In addition, there is very likely a threshold to how fast one can put on healthy weight and fat gain should be considered.

Potential Fat Gain

Because any weight gain ultimately includes some amount of fat gain in addition to muscle, effects on body composition are an important factor when deciding on a bulking meal plan. Even if you are able to promote rapid lean tissue growth, if you end up gaining a large amount of fat along with it, you'll likely need to cycle through a fat-loss diet (cut) soon after to achieve the end result you are looking for.

In the first study mentioned above, higher caloric intake promoted an increase in total lean body mass but also resulted in a significant amount of weight gain from body fat.

*Graph illustrates total body weight (weight gain) and % gain of lean body mass/muscle (LBM) and fat mass (FM) between a group with a nutritionally prescribed higher calorie intake (NCG) and an ad libitum/ lower calorie intake group (ALG).

And the second study above looking at varying protein levels suggests that protein intake is also key in preventing fat gain. If protein intakes are too low, there aren't sufficient amino acids available to build muscle, and excess calories will lead to more body fat. In addition, some studies suggest that if more of your excess calories are coming from protein, they may be more likely to promote lean mass over fat gain (3,4,5). But these effects seem to tap out once optimal protein needs are met, around 25% of total calories.

The amount of fat you can gain might be more closely related to your fitness level, with untrained individuals more prone to put on lean mass compared to those who have been strength training for some time and have already gained a good amount of muscle, to begin with (6). This would explain how a 2,000-calorie surplus in untrained individuals could result in nearly 100% weight gain as muscle in one study (7).

The Winner

Based on limited research between the two bulking diets, a slower and more macro-focused approach to weight gain, such as a lean bulk, is likely going to result in more muscle mass and less body fat gain than a rapid approach. However, your starting fitness level and body composition can strongly affect what type of weight you are able to gain and how quickly.

Nutrition

We know that building muscle requires an increase in protein and calories combined. And while we can continue to argue over whether or not a clean bulk or dirty bulk approach supplies these to the diet best, overall nutrition should also be factored in.

Certain vitamins and minerals are important for supporting muscle growth. Nutrition is also key for recovery, reduced risk of disease, and improved energy, mood, and overall well-being. So including more nutritious food options into your bulking diet could offer additional advantages.

Lean bulking usually emphasizes more nutrient-dense, whole foods and has the potential to supply more nutrients than a dirty bulk loaded with heavily processed foods and empty calories. Studies suggest that vitamins A, C, and E may play a role in supporting muscle growth, and these vitamins are most commonly found in fruits and vegetables (8). In addition, adequate intakes of B vitamins, zinc, vitamin D, and calcium are also thought to be important, with meat and dairy being the best sources (9).

And it's not so much the amount of food you are eating but the type of foods that matter. Even at higher calorie levels, nutrition deficiencies occur - a large number of people in this country are overfed and undernourished (10). If a majority of calories are coming from high-fat, high-sugar, or heavily processed foods, you could be missing out on a lot of essential nutrition to support your muscle-building efforts.

There are also the health concerns of consuming a diet high in not-so-healthy ingredients, like added sugar, trans fats, saturated fat, cholesterol, sodium, etc. Higher intakes of heavily processed foods have been linked to a number of chronic diseases and increased inflammation (11,12,13,14,15,16,17). And while these concerns may not directly affect your ability to build muscle mass, poor food choices can really add up and negatively impact your life over time. Clean bulks also set you up for more success on a maintenance diet following your bulk, since you are continuing to instill healthier habits.

The Winner

Proper nutrition beyond macro balance and protein intake may offer added benefits for your health and muscle growth capabilities. A lean bulk is likely more apt to offer a more nutritious approach to bulking, but a basic understanding of nutrition with an emphasis on more nutrient-dense foods is needed.

The Verdict

Both methods of bulking offer unique benefits, and like most things the best diet for you likely depends on the person. However, based on the existing research, lean bulks are likely your best bet for adding more lean mass and setting yourself up for more success and better results in the long run.

Dirty-Bulk-vs-Clean-Bulk-(1)

* Chart is based on cumulative research and assessment noted above.

Meal Prep for Muscle Gain

Sticking to a bulking diet might sound easier than it is. For many, it can be a challenge to get enough calories consistently and master their lean bulk macros for optimal results. Learning how to meal prep for muscle gain is a great start to help keep you on track and ensure you are hitting your nutrition goals consistently.

Get your bulking diet down to a science with this free meal prep toolkit for muscle building. A comprehensive guide with custom macro calculations, food lists, meal planning templates, and tips from the pros.

Not into prepping? How about a meal delivery program that cooks your food and delivers quality, nutrient-dense proteins, grains, and veggies to make the dieting side of gaining muscle a breeze? Trifecta's A La Carte options are built for customized meal prep. It's also a favorite of Trifecta athlete, Mike Rashid.

Dirty Bulk vs. Clean Bulk: What is the Best Muscle Building Diet?

Bulking Diets

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Rate of Muscle Growth

The Winner

Potential Fat Gain

The Winner

Nutrition

The Winner

The Verdict

Meal Prep for Muscle Gain

Additional References

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