Summary

Beginners and people with relatively high body fat percentages can gain muscle mass & strength in a calorie deficit (also known as a cut or fat loss program).
A dirty bulk might lead to quicker muscle gains but also greater fat gains.
Intermediately trained lifters might be able to gain in a deficit, as well. If your body fat is low and you are well trained, it’s safer to go for a slow/lean bulk.
Studies suggest that it's harder to gain muscle mass compared to strength in a deficit, if you’re trained. But, you might be able to do both depending on the factors listed in this article.
Here is an overview of the deficit gaining and body recomposition studies

Definitions

Untrained = Someone who is new to lifting. A beginner.
Trained = These are intermediately trained lifters. Usually, they will have 2+ years of experience with strength training.
Advanced = These are typically athletes or bodybuilders. They are very strong in relation to their body weight, and usually have considerable amounts of lean mass (i.e. rugby players). Or, they could be bodybuilders with a lot of lean mass and low body fat %.

Can we gain muscle in a deficit?

The preponderance of the evidence suggests that both beginners, novices, intermediates, and even advanced athletes can gain muscle and strength while losing fat. You can find an overview of the deficit gaining and body recomposition studies further down in the article.

Things to keep in mind:

We might lose muscle mass if we cut calories without doing strength training (Villareal et al., 2016). Hence, it’s important to do strength training while cutting to avoid muscle loss (Stiegler and Cunliffe 2006; Miller et al., 2013; Churchward-Venne et al., 2013; Trexler et al., 2014; Helms et al., 2014a; Helms et al., 2014b; Murphy et al., 2014; Hulmi et al., 2016). But in older adults, aerobic training in itself could preserve more muscle mass than being sedentary (Weinheimer et al., 2010).
Cutting should be done with small or moderate deficits (i.e. around -500 kcal) to avoid loss of muscle mass (Garthe et al., 2011; Sundgot-Borgen and Garthe, 2011; Trexler et al., 2014; Helms et al., 2014a; Murphy et al., 2014; Khodaee et al., 2015; Manore et al., 2015; Hulmi et al., 2016). Very low calorie diets might lead to more muscle atrophy (Chaston et al., 2007).
There are other negative effects of rapid weight loss (hormonal, physiological, and psychological) (Sundgot-Borgen and Garthe, 2011; Franchini et al., 2012; Trexler et al., 2014; Khodaee et al., 2015; Manore et al., 2015; Hulmi et al., 2016; Aloui et al., 2016; Hulmi et al., 2016). I will review this in more detail in another article.
You might want to eat a high-protein diet when you go on a cut to preserve muscle mass (Stiegler and Cunliffe 2006; Wycherley et al., 2012; Churchward-Venne et al., 2013; Pasiakos et al., 2013; Phillips, 2014; Trexler et al., 2014; Helms et al., 2014; Helms et al., 2014a; Murphy et al., 2014; Manore et al., 2015; Kim et al., 2016; Hulmi et al., 2016).
For example, 1.5-1.8 grams protein per kg bw (Phillips, 2014; Murphy et al., 2014; Hulmi et al., 2016). Maybe even more (i.e. >2 grams per kg bw) (Phillips, 2014; Murphy et al., 2014; Helms et al., 2014).

“While greater deficits yield faster weight loss, the percentage of weight loss coming from lean body mass (LBM) tends to increase as the size of the deficit increases ”

- Helms et al., 2014a

Deficit gaining, recomping, or bulking?

We are similar, yet different

Athletes have different levels of success when bulking, as shown in the graph below. The same is true for cutting (Garthe et al., 2011). Not everyone can gain muscle and lose fat at the same time. It might depend on factors like:

Age
Gender
Training level (Helms et al., 2014b),
How steep the caloric deficit is (Helms et al., 2014a; Robinson et al., 2015; MacKenzie-Shalders et al., 2016)
Your protein intake (citations further up)
Diet and training program adherence
Body fat. Low body fat increases your risk of losing muscle mass (van der Ploeg et al., 2001; Rossow et al., 2013; Kistler et al., 2014; Murphy et al., 2014; Robinson et al., 2015; Huovinen et al., 2015; Hulmi et al., 2016).
How much and which type of cardio you do (i.e. interference effect) (Helms et al., 2014b)
How close you are to your genetic potential

Garthe et al., 2012 - Athletes respond differently to bulking.

A great deal of studies show that there are high-responders, low-responders, and non-responders to training. This means that our bodies react differently to similar training programs and diets. I won’t go into details here, but check out my article on it, and Greg’s, as well.

Cutting with little body fat

You might be more likely to lose muscle mass if you cut calories when your body fat is already low (i.e. below 7-10% for men) (Rossow et al., 2013; Helms et al., 2014a; Kistler et al., 2014; Huovinen et al., 2015; Robinson et al., 2015). In two studies on women bodybuilding competitors, they lost fat and muscle mass during contest prep but it was probably because they hit 12% body fat by the end (van der Ploeg et al., 2001; Hulmi et al., 2016). This is very low for women! To illustrate it, women suffering from anorexia nervosa have 9-13% body fat (Mayo-Smith, 1989; Mayer et al., 2005). The menstrual cycle can stop when body fat becomes very low (Halliday et al., 2016). Some suggest 12% for women is akin to 4% for men. Here’s a comparison image from Builtlean:

I don’t want to encourage you to drop to unhealthy bodyfat levels that are akin to eating disorders. So please consider your level of body fat before you decide to restrict calories. Drastic calorie reductions might lead to disordered eating (Manore et al., 2015). Although, this shouldn’t be a problem for most of us since we’re more likely to have too much body fat rather than too little.

What is the best method to gain muscle and lose fat?

Preface

“The best method” depends on your diet and program (Helms et al., 2014b). As we see in the graph below, some women were able to gain lean mass, but most did not (though they did go to very low body fat levels, which affects gains!). They all used their own diets and training programs.

Figure by Hulmi et al., 2016

With that caveat out of the way, let’s see what the research has to say.

Bulking

Bulking (eating in a surplus) is the traditional way of gaining muscle mass. You can gain slowly (lean bulk) or quickly (dirty bulk). It’s sometimes said that a dirty bulk is better for putting on muscle mass, but you will also gain a lot of fat at the same time (Garthe et al., 2012). In the figure below, the dirty bulk group gained a lot more fat than the lean bulk group.

“The excess energy intake in a weight gain protocol should (...) be considered carefully since greater rates of gain are likely to include larger increases in body fat storage in already strength-trained athletes” - Garthe et al., 2012

Bar chart by Garthe et al., 2012 (Edited for clarity) - The white group (NCG) ate ~3600kcal, black group ate ~3000kcal

Some have pointed out that the amount of energy you consume affects how much muscle you can build:

“a significant correlation between total energy intake and gains in lean mass (r = .43, p = .04) was demonstrated” - MacKenzie-Shalders et al., 2016

Others support this idea as well, the more energy and protein you consume, the more gains. From a metabolic ward study:

Figure by Bray et al., 2012 - Note that the participants were in a metabolic ward and they did not strength train during the intervention and still gained LBM. High and medium protein groups increased their energy expenditure by about 200 kcal by the end of the study

Though if you don’t consume enough protein, the extra energy is stored as fat, as you can see in the low-protein group (same study):

Bar chart by Churchward-Venne et al., 2013, based on Bray et al., 2012. This shows us that it’s necessary to consume enough protein if we want to gain LBM.

"With the low protein diet, more than 90% of the extra energy was stored as fat. Because there was no change in lean body mass" - Bray et al., 2012

In conclusion for bulking, there's some evidence that more calories might lead to greater LBM gains, but the evidence isn't very strong and we need more studies.

Gaining in a caloric deficit

It is possible to gain muscle mass and strength in a caloric deficit, but there are many factors that decide whether it will work for you or not. It’s probably a good idea to go for deficit gaining if you’re overweight, or a beginner/novice. If you’re both, even better.

If you are, however, a lean athlete with years of strength training experience, it might work, it might not. I can’t speak in certainties. You could try it, just make sure to keep protein high (i.e. 2g per kg bw), go for a slow cut (maximum -500kcal per day), get enough sleep & recovery, avoid excessive stress, have the right genetics, and use a solid strength training program. The better your body composition is, the harder deficit gaining will be for you, in all likelihood (Helms et al., 2014b; Rossow et al., 2013; Kistler et al., 2014; Huovinen et al., 2015). The graph below shows that endurance athletes with lower body fat %, lost FFM on a cut. Those with body fat over 10% did not.

Correlation by Huovinen et al., 2015. Note that they didn’t follow a strength training program in this study and that the sample size was small.

Gaining strength is easier, because more studies suggest that you can gain strength even if you’re quite well trained (see the study overview table above for details).

Bar chart by Garthe et al., 2011 - Novice/intermediate lifters gain more strength on the BP during a slow cut (SR) compared to a quick cut (FR).

Overview of Studies

There are several studies that suggest beginners and novice/intermediate lifters can gain muscle and strength while losing fat. Note that we've excluded several studies from this table. For example, studies with unhealthy subjects, low protein intakes, and some studies where participants didn’t strength train. I do this because it’s normal to lose muscle mass when subjects don’t lift or eat enough protein.

Note: there's also a substantial amount of studies where subjects lose both fat mass and lean body mass. These studies will be included in a forthcoming article.

Body Recomposition and Deficit Gaining

Untrained Subjects

Trained Subjects

Reviews

Study & Subjects	Results
Sigal et al., 2014 N = 304 Duration: 22 weeks Diet: not controlled Untrained 14-80 y.o. boys and girls	Hypertrophy Not measured Fat mass Decrease Strength Gain
Treuth et al., 1994 RCT N = 22 Duration: 16 weeks Untrained 60 y.o. men	Hypertrophy +2 kg fat-free mass Fat mass -2 kg fat mass Strength Gain
Donnelly et al., 1993 N = 14 Duration: 13 weeks Untrained obese women 800 kcal diet (VLED)	Weight 16 kg weight lost Hypertrophy 24% weight lost was from FFM (glycogen/water mass loss?) Gain in muscle fiber CSA Fat mass 76% weight lost was from fat
Demling and DeSanti, 2000 N = 38 Duration: 12 weeks Untrained 34 y.o. overweight men	Hypertrophy Strength training groups gained 2 and 4 kg FFM Fat mass Mean fat loss 2.5 to 7 kg over 3 different groups Strength Strength increased 29% and 59%
Arazi and Asadi, 2011 N = 39 Duration: 1 + 8 weeks Untrained 20 y.o. men	Hypertrophy Increased arm circumference Fat mass Decrease Strength Increased
Nindl et al., 2000 N = 31 Duration: 24 weeks Untrained 28 y.o. women	Hypertrophy 2.2% increased LBM Increased rectus femoris CSA and total thigh CSA Fat mass 10% decreased fat mass
Palumbo et al., 2017 N = 16 Duration: 12 weeks Untrained ~31yo women	Weight Total body mass unchanged (recomposition) Hypertrophy Gained ~1.2 kg LBM (DXA). LBM gains were only significant to the limbs they were training (upper-body group vs lower-body group) Fat mass Lost ~1.7 to ~2 kg fat
Josse et al., 2010 N = 20 Duration: 12 weeks Untrained 23yo women BMI = 25-26	Hypertrophy ~2 kg gain in LBM Fat mass Lost 1.6kg fat Strength Strength increased in all exercises by 52–103%
Consolazio et al., 1975 N = ? Duration: ~6 weeks Untrained men	Hypertrophy Protein group gained 3.28 % LBM Fat mass Protein group lost 2.21 kg fat mass
Eliot et al., 2008 N = 42 Duration: 14 weeks Untrained 48–72yo men	Hypertrophy Whey Protein group increased arm bone-free FFM by 8.2% (), and whole-body BF-FFM by 0.7 kg (non-significant) Fat mass* Fat mass was completely unchanged (0 kg). Body recomposition
Verreijen et al., 2017 N = 100 Duration: 10 weeks Untrained 55–80 yo obese men	Results for PRO+EX group Hypertrophy Gained 0.5kg LBM Fat mass Lost 3kg fat mass
Meirelles and Gomes, 2016 N = 21 Duration: 8 weeks Beginners, 34–45 yo overweight and obese men and women	Body recomposition Hypertrophy Maintained muscle thickness Fat mass Body fat decreased 3–5%, waist circumference decreased by ~4 cm Strength 14–19% increase in strength
Marks et al., 1995 N = 44 Duration: 20 weeks Inactive, overweight 20–49 yo women	Weight Body mass loss for intervention groups was between -3.7 to -5.4 kg Hypertrophy All groups maintained FFM Strength Strength 1RM increased significantly for both groups.

Study	Results
Burke et al., 2001 N = 42 (23 in final analysis) Duration: 6 weeks Trained (4+ years RT) 18–31 yo men	Body recomposition Hypertrophy Whey group increase LBM by 2.3 kg* Fat mass Fat mass decreased by 0.6 kg (not significant) Strength Strength 1RM gains
Hartman et al., 2007 N = 56 Duration: 12 weeks Previously trained / retraining 18-30yo men	Results for Milk protein group Hypertrophy Bone-free FFM increased by 3.9 kg* Type II muscle fiber CSA increased by about ~36.5%* Fat mass Fat mass decreased by 0.8 kg* Strength Mean 1RM incline leg press increased by 102% (from 186 kg to 377 kg)*
Kerksick et al., 2006 N = 36 Duration: 10 weeks Trained 31yo men (5.3 years training experience)	Body recomposition Hypertrophy Whey and Casein group gained 1.9 kg LBM* Fat mass Fat mass was unchanged (0.1 kg) Strength Bench press increased by 8 kg*
Longland et al., 2016 N = 40 Duration: 4 weeks Trained (advanced, retraining) 23yo men Supposedly, they were detrained football players retraining.	Hypertrophy Increased LBM by 1.2 kg Fat mass Lost 4.8 kg fat Strength Added 170 kg to their leg press and 40 kg to their bench press.
Cribb et al., 2007 N = 26 Duration: 11 weeks Trained ~24–25yo men Mean training experience = 4-6 years. ~100kg 1RM bench at baseline, body mass=70 kg for Whey Protein group	Results for Whey Protein group Body recomposition Hypertrophy Gained 1.3kg LBM () Muscle fiber CSA increased () Fat mass Fat increased 0.4 kg (non-significant) Strength Added ~20 kg to their bench press (*)
Garthe et al., 2011 N = 30 Duration: 8.5 weeks for slow cut group Novice and intermediate lifters ~21yo men and women (Norwegian athletes)	Body recomp for fast cut, but deficit gaining for slow cut Hypertrophy Slow cut increased LBM by 2.1%* Fast cut maintained LBM Fat mass Slow cut lost 31% Fast cut lost 21% Strength Bench press and squat 1RM strength gains were 12–14%.
MacKenzie-Shalders et al., 2016 N = 24 Duration: 6+6 weeks Trained elite rugby 20 yo male athletes Baseline mean body mass = 101.5kg, 75.5 kg LBM (Maybe on steroids or genetic elites)	Hypertrophy Added 2.7 kg LBM in 12 weeks Fat mass Lost about 2 kg fat
Hoffman et al., 1990 N = 61 Duration: 10 weeks Trained 20 yo men Baseline BW between 75 and 125 kg. Bench press 1RM between 95.6 and 156 kg	Weight Lost body weight Hypertrophy Gained chest and thigh circumference Strength Increased strength
Crewther et al., 2016 N = 24 Duration: 4 + 4 weeks Trained ~30 yo men (2+ years RT experience 3x per week)	Hypertrophy FFM increased (skinfolds) Fat mass Decreased BF (-5.7%) Strength Both groups gained squat and BP 1RM strength
Dudgeon et al., 2017 N = 16 Duration: 8 weeks Intermediately trained (RT for 2 years) 21–28 yo men Baseline: ~67 kg LBM and ~12 kg fat	Results for protein group Body recomposition Hypertrophy Maintained LBM Fat mass Lost fat mass Strength Gained strength
Hulmi et al., 2016 N = 50 Duration: ~20 weeks Trained 27 yo Women (IFBB competitors) (3.5 years RT experience) Contest prep	Hypertrophy Note: only some of the women increased FFM. Most lost FFM Fat mass They lost about ~9–10% body fat. They hit ~12% BF.

Limitations

Measuring FFM with DXA is imperfect, but not useless

DXA and FFM measurements are imperfect (also read the section below: Glycogen/water mass can affect beginner gains).

For trained athletes, SEM is a couple of % for fat, and around 1% for FFM, according to Garthe et al., 2012 and their repeated DXA measure tests.

“For DXA reproducibility, 10 male and female athletes did two repeated measurements within 24 hours, and the coefficient of variation in DXA Lunar Prodigy total body scan for repeated measurements was 3% for FM and 0.7% for LBM.” - Garthe et al., 2012

Others find little difference between DXA and MRI measurements:

“Dual-energy X-ray absorptiometry and magnetic resonance imaging fat mass measurements showed good agreement (r = 0. 72-0.92); their lean mass measurements were similar as well, showing approximately 5.5% increases in leg lean tissue.” - Nindl et al., 2000

This is just a snapshot from two studies. I will have to write a separate article on body composition measurements, and look at the literature in its totality.

Glycogen/water mass can affect beginner gains

Beginners gain glycogen and water mass when they first start strength training programs. I've previously written about this here. This is a bit of an issue since "noob gains" are partially glycogen/water gains (Ribero et al., 2014). This affects lean body mass (LBM), fat free mass (FFM), or cross-sectional area (CSA). Muscle glycogen/water content even affects MRI measurements (Nygren et al., 2001). But, there are several studies that show beginners lose or maintain FFM when they go on a cut. Probably due to a reduction in carb (glycogen) or protein intake. Hence, it’s not a given that beginners will increase FFM when they train and cut.

In trained lifters, it is unlikely that FFM increases are glycogen/water mass. Here’s why:

Trained lifters already had their "noob gains" for glycogen/water mass. These water gains come relatively quickly when we first start to train (Ribero et al., 2014).
In a deficit, we eat less carbohydrates. Carb intake regulates muscle glycogen stores. If anything, glycogen stores will shrink slightly in a deficit.

Comparing gains/fat loss across studies with different methodologies is difficult

There are few studies that directly compare bulk/cut vs. recomp vs. deficit gaining

Other considerations

Several of the studies have deficit gaining as a secondary outcome (i.e. they're testing other things in the study, while the deficit gaining is more of a side-effect)
Fitness research is based on probabilities and averages. Some people might be able to gain in a deficit, some may not be. Many factors affect whether you will be able to successfully gain in a deficit.
Survivor bias: Several of the studies had many dropouts. This means that only those that “survived” the study, are measured and evaluated. Those that had no improvements might have become frustrated and dropped out. This could inflate the study results (muscle gain/fat loss).
In some studies, i.e. Ploeg et al., 2001, the women who were preparing for a bodybuilding contest did excessive cardio (10h per week), for part of their prep period. They lost FFM, but they might have been able to avoid that if they didn’t do so much cardio (interference effect) (Helms et al., 2014b). They also dropped down to very low body fat levels.

Review	Quotes
Josse and Phillips, 2012	“Milk and other dairy foods (...), in combination with resistance exercise (...), have been shown to consistently improve body composition in women under both iso- and hypoenergetic conditions.”

Gaining Muscle Mass in a Deficit vs. Bulking (Research Review)

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