Nutrition for Muscle Growth
Overfeeding, Lean Bulking, and Dream Bulking.
If you wanted to gain muscle — how would you do it? Do you need to be in a caloric surplus? What are the ideal macronutrient intakes? What ratio of muscle:fat can we expect? What rate of gain should we use? In this post I’ll dig into the research to find out just how much we know about all of these questions.
Table of Contents
- P-Ratio
- Sedentary Overfeeding
- Overfeeding with Resistance Training
- Macronutrients & Overfeeding
- Summary & Recommendations
- Rate of Gain
1. The P-Ratio
The P-ratio first appeared in the literature in the late 1970s and was thought to be constant for each individual (Dugdale & Payne, 1977; Payne & Dugdale, 1977b). The P-ratio is the the fraction of an energy imbalance accounted for by changes of the body’s protein reserves. More simply, it means what portion of lean mass we gain (or lose) for every unit of body weight change. The idea was further studied by Dr. Gilbert Forbes in late 1980s after observing that people who are in a larger energy deficit lose more weight.
This led him to ask two key questions:
- Does the converse hold true for excess energy intake, and do such gains involve fat mass, lean mass, or both?
- Do thin people gain weight less easily than those who are overweight?
His seminal paper from 1986 is not what you would see in modern research — he combined his own experimental data with observations from the literature into one analysis. In the experimental portion he established maintenance calories in subjects, then overfed them by 717 kcal for 2 days, followed by overfeeding them with 1195–1793 kcal per day for the next 15–19 days, which resulted in a total of 17–21 days of overfeeding. The subjects gained 3.5–5.8 kg of bodyweight, and 51% of their weight gain consisted of lean body mass (LBM).
In the second part of the manuscript he combined data from his these participants with data extracted from the literature and created an equation:
y = 0.275+0.0305x
This means that for every one unit (MJ) of excess energy there will be a .03 kg unit increase in lean body mass. For reference, a megajoule (MJ) is ~239 kcal. This actually doesn’t tell us much because all of these studies ranged from 2–7 weeks, which is a large difference.
We also need to remember this is mostly cross-sectional data. In fact, subjects from Forbes’ participants (dark triangles) accounted for 15 out of a total of 48 data points in the analysis. This graph only represents 48 people (15 females, 28 males). I think it’s also important to note some of these studies were done in anorexic patients. You rarely see this type of data in current research because we have newer methods (e.g., meta-analysis) that can account for the variability between studies. Forbes’ results indicated:
Forty of the forty-three subjects… sustained an increase in LBM in response to over-feeding…. the average composition of the weight gain was 38% lean and 62% fat; based on means, these values are 44% lean and 56% fat. In earlier studies of adult men overfed for 6 months Keys et al. (1955) found by densitometry that 40% of their weight gain could be ascribed to LBM.
He also found that the variations in response to overfeeding could not be explained by sex, initial body-weight, initial fat content, duration of overfeeding, type of food eaten, or the amount of daily food consumption. This pretty much rules out everything except genetics. He would revisit the idea soon thereafter.
To summarize: Forbes found that only ~38% of the increase in body weight was due to lean body mass (LBM) and 62% was fat mass.
Enter Bouchard et al., 1990:
Claude Bouchard is a legend in the field of exercise and nutrition. His studies of twins in the 90s help us understand how genetics play a role in overfeeding. He studied twelve twins in a highly controlled environment for 100 days. The twins were overfed by ~1000kcal per day for 6 days per week and ate at maintenance on the 7th day. The average weight gain was 8.1kg with a range of 4.3–13.3 kg. On average twins gained 5.4 kg of fat and 2.7kg of LBM. That translates to a ratio of 34% lean mass and 66% fat mass, which is similar to what we saw in Forbes’ analysis. Interestingly, there was at least three times more variance between twins than within twins. This means that genetics — the thing we can’t change — is a big determinant of how we adapt to overfeeding.
Bouchard also observed that people deposit fat in different areas, which suggested that we have no control over that too:
some individuals are storing fat predominantly in selected fat depots primarily as a result of undetermined genetic characteristics. It also suggests that variations in regional fat distribution are more closely related to the genotype (genetics) of the individuals than are variations in body mass and in overall body composition.
We may not have control over where we store our fat or our genetics, but we do have control over our body fat levels.
Forbes re-enters the Fray
Forbes revisited the idea of proportional changes in 2000 (Forbes 2000). He observed that the relative contribution of lean mass gain to total body weight gain is an inverse function of body fat. Put simply, the more fat you start with the less LBM you’ll gain. However, this idea is based on a small number of cross-sectional studies which is a big limitation. You can also see in the graph that once we hit 20kg of fat mass the ratio of LBM changes are similar, which makes me wonder if there is a threshold for which we need to stay under/over to optimize LBM gains.
Hall models losses in LBM
Skipping forward to 2007, Dr. Kevin Hall revisits Forbes’ idea (Hall 2007). However, Hall was much more interested in modeling body weight losses (i.e., after bariatric surgery) than gains and therefore doesn’t add any new information to our story. He also focused on large (e.g., 20–30kg) changes in body weight, which don’t generally apply to those who are trying to gain muscle. I think the paper is best summarized by this quote, which leads to even more questions:
Forbes’s theory is a convenient model for body composition change in humans, but many questions still remain. For example, is it true that longitudinal changes follow the cross-sectional relationship of FFM versus FM? Furthermore, it is unclear whether the FFM versus FM curve would be followed over the entire time course of weight gain and loss, or only after the transients have dissipated and a new steady-state is achieved.
Summary of Changes in LBM and FM
In summary, we now know that our P-ratio is driven by genetics, may be affected by body fat levels and probably falls somewhere between 55–65% fat mass and 35–45% lean mass per unit (pounds or kilos) of change.
2. Sedentary Overfeeding
To give more context to the research on overfeeding let me introduce two more recent studies that report macronutrients.
In 2010 Ernersson and colleagues asked 18 participants to double their energy intake by eating at least two fast food meals per day for 4 weeks (Ernersson 2010). This led to an average energy surplus of 70% compared to their normal intake with a macronutrient composition of 12% protein (2.4 g/kg), 43% fat, and 45% carbohydrate. At the end of the study participants’ body weight increased by 6.4 kg, consisting of 58% LBM and 42% FM. These numbers are already better than what Forbes found probably because of the high protein intake. However, this study relied on food logs which can suffer from under or over-reporting (Gemming 2015) although it does give us an idea of how overfeeding could work in the real-world (i.e., ecological validity) if we just tell people to “eat more”.
To further explore the role of protein, Bray et al., overfed participants by 40% of their maintenance calories using three different protein intakes (0.7, 1.8 or 3.0 g/kg) for eight weeks in a metabolic ward (Bray 2012). As depicted in the graph, the low protein group (0.7g/kg) didn’t gain any LBM while the moderate (1.8g/kg) and high protein (3.0g/kg) groups did. This tells us that protein is very important for LBM changes, independent of exercise. It also tells us that it’s possible to gain predominantly fat on a low protein diet.
Bray and colleagues show the moderate protein group increased body weight by 6kg consisting of 52% LBM and 48% FM while the high protein group increased body weight 6.5kg consisting of had 49% LBM and 51% FM. This suggests there may be a protein threshold for increases in LBM somewhere around ~1.8g/kg in a sedentary setting.
I’ve included these two studies so we have some idea of the proportional changes in a population that is similar to people who want to gain muscle (and are not diseased). All of this culminates in something most people know —we need to eat protein if we want to gain lean body mass.
3. Overfeeding with Resistance Training
If our goal is to maximize muscle growth then we need to exercise. Specifically, we need to resistance train. The next few studies use participants with varying amounts of training experience to help us determine when or if we need to overfeed and to what extent.
Let’s begin with a study on relatively untrained participants (baseline bench press = ~73–85kg) from the early 2000s (Rozenek 2002). The training program was a typical upper/lower split (2x per week) for 8 weeks. The study had three groups with two of them consuming +2000kcal per day (CHO; PRO+CHO) over their baseline diet. Nutrition was recorded via 3-day food logs. This study also had a control group, which helps us put things in perspective and answer the question:
Does being in a surplus enhance gains as a beginner?
This experiment was initially designed to test a supplement containing 356g CHO, 106g PRO, 18g fat vs an isocaloric supplement with 450g CHO, 24g PRO, 14g fat. This caused the PRO group to consume more protein (3g/kg/day) with the same surplus (+2000kcal/day). A graph of the data shows us that every group gained LBM: the CHO supplement gained the most LBM (3.4kg), the PRO+CHO group gained 2.9kg LBM and the control group gained 1.4kg LBM.
If we look at FM we can also see some interesting data. The CHO and CON groups underwent a pure recomposition by losing fat and gaining muscle, while the PRO+CHO group gained 0.2kg of FM. So, eating in a 2000kcal surplus per day the PRO + CHO gained mostly LBM and the CHO group lost FM. We know body recomposition can occur in new trainees, but these results are impressive. They were eating +50% kcal over baseline per day. Overall, I’m a little skeptical of these results and if they truly apply to a physique athlete.
In summary, this study tells us there isn’t much of a difference between 1.7g/kg and 3 g/kg of protein for increases in LBM, but there seems to be a benefit for being in a surplus when you’re new to training. Practically speaking, this is probably the safest time to be in an aggressive surplus to maximize your growth. I wouldn’t recommend eating +2000kcal per day as these subjects did, but keep reading to see my practical recommendations at the end of the article.
Moving on to moderately trained subjects
Garthe et al., compared two groups of athletes who were randomized to a nutritional counseling group (NCG) or an ad libitum group (ALG). Ad libitum means free eating. They completed a typical resistance training program (2x upper/lower per week) in addition to their sport practice (16h/week). They were told to aim for a bodyweight increase of 0.7% per week. Ultimately, while nutritional counseling did increase one group’s average caloric intake by +500kcal, only 38% of the athletes in counseling group and 6% in the ad libitum group reached their weight gain goal. If we compare LBM and FM gains between the groups we can see that the nutritional counseling group gained 1.7kg LBM and 1.1kg FM (60% LBM; 40% FM) while the ad libitum group gained 1.2kg LBM and 0.2kg FM (85% LBM; 15% FM).
This study agrees with Rozenek 2002, such that you can increase LBM without a surplus, in this case, even if we do have a large amount of sport training. Another interesting difference in the two groups was protein intake — the NCG group ate 2.4g/kg while the ALG group ate 1.7g/kg. Both of those are within current recommendations for sport athletes and fit well with the previous study mentioned.
Next, in a well designed study, trained males were overfed by 1250 kcal per day while resistance training for eight weeks (Spillane & Willoughby 2016). The results show that the low protein group (1g/kg) had a ratio of 14% LBM and 86% FM gain while the moderate protein group (2.4g/kg) had a ratio of 59% LBM and 41% FM. Ultimately, the low protein group gained only .25kg of LBM while the high protein group gained 2.28kg of LBM. This tells us that extra calories in the form of protein could lead to better LBM gains.
Moving on to highly trained subjects
We’ll use one more study to help us understand the effects of overfeeding with training (Ribeiro 2019). Bodybuilders were randomly assigned into one of two groups: a high energy group (G1, 67.5 kcal/kg/d), or a moderate energy (G2, 50.1 kcal/kg/d) for 4 weeks. The calorie intake was at the higher end, but comparable to the physique literature since it fell between 25–66 kcal/kg/day (Spendlove 2015).
The high energy group gained 1.1kg FFM and 1.2% body fat while the moderate energy group gained 0.4kg FFM and 0.1% body fat. Practically speaking, it’s easy to see that the moderate energy group had a much better ratio of change but the authors don’t report the data so we can’t calculate the exact ratios.
What can we learn from this study? Well, it’s a little harder to interpret because they used skin calipers and estimated muscle mass, so we can’t compare lean mass or fat mass changes directly. We can, however, see just how much variability exists between participants which is highlighted by the authors:
A large inter-individual variability was noted for body fat changes in the G2; while two participants reduced body fat from pre- to post-study, the other three participants showed an increase. Participants in the G1 displayed more consistent body composition outcomes, individually showing accretion of both muscle mass and body fat.
Taking a more practical approach, I wanted to compare my intake to what would be prescribed if I was in this study since I’m well past the intermediate level, and a natural bodybuilder although not elite. If I was in the high calorie group I would be eating ~4,720 kcals and if I was in the moderate calorie group I would be eating ~3,520. Both of these are much, much higher than what I actually consume, so I would be cautious with applying this specific energy intake to yourself.
Overfeeding with Resistance Training Summary
- People new to training can gain lean body mass without a surplus, but will gain more with one.
- Athletes who receive counseling are more likely to stick to a surplus. This may help for those who struggle to eat enough.
- A higher protein intake leads to larger gains in lean body mass, up to a point (~1.7–1.8g/kg/day). It also appears that overfeeding with protein and carbohydrates may be better for LBM:FM ratios. More on this in the next section.
- There is a lot of inter-individual variability with overfeeding therefore we must be careful when using recommendations with higher level physique athletes. Adjustments are needed if we gain too quickly.
These are very large ranges, which allows for a lot of flexibility. There’s an inherent issue with guidelines of this type — we just don’t have much data. Spillane used +1250kcal and Garthe et al., ended up with +500kcal. They both used dietary logs, trained people for 8–12 weeks, and were intermediate lifters or below. Therefore, it’s very difficult to recommend general guidelines for people from these two studies, so I have to use my anecdotal coaching experience to help guide us. If you want to be conservative and possibly stay in a surplus longer then you would want to be around +200kcal, but if you’re new(ish) to training then you can probably push it to +750kcal to maximize gains. I also think there is an inherent benefit for being in a caloric surplus longer compared to cycling in and out of surpluses and deficits over short periods.
Here’s an example of my current maintenance calories and a conservative vs aggressive approach to overfeeding. As you can see the calorie difference between the two is roughly 3500kcal per week. I also wanted to add in some context that most people forget: data variability. How closely do you track? If you use a food scale it’s not too hard to be within ~100kcal of your goal. However, if you travel a lot or eat out it becomes more difficult. Furthermore, if you’re intuitively eating you may want to stay on the conservative side whereas if you track everything closely you could be slightly more aggressive. We also need to have body weight checkpoints to adjust.
4. Macronutrients & Overfeeding
Next we need to see where we would allocate those extra calories or how we would split up our macronutrients. For that we’ll start with protein since it is the most important macronutrient for muscle growth.
4.1 Protein
A series of studies was completed by Dr. Jose Antonio over the past 5–6 years that have really shed light on the importance of protein for gaining muscle. He used high levels of protein in all of his studies which accounted for varying surpluses. Let’s dive in.
In study #1 he recruited trained subjects for 8 weeks and gave them moderate or high protein and asked them to continue their normal exercise. Importantly, the higher protein group had a +800kcal surplus (from protein). He found that those on the higher protein diet gained more fat-free mass (FFM) and lost fat mass (FM) compared to the moderate protein group.
In study #2 he recruited subjects and trained them for 8 weeks. These were slightly different protein intakes than the first study, with a +500kcal surplus for the higher protein group (3.4g/kg/day). There weren’t any differences in FFM intake, but the higher protein group did have a small FM loss, similar to the 4.4g/kg group in the first study.
In the final study he used a crossover design to compare high (2.6g/kg) vs higher protein (3.2g/kg) intake for 16 weeks. The higher protein group consumed a +400kcal surplus. When comparing changes he found a 1.1kg FFM increase and, again, FM decrease with the higher protein group.
If we plot all of these together we can see a pattern start to appear. Higher protein intake is probably better for FFM gains, with a benefit of potential FM loss. Now, I don’t think these necessarily apply to high level athletes, but I think it could apply to some intermediate levels. Therefore, you probably want to be between 2.3–3.4g/kg of protein per day to optimize muscle growth and minimize fat gain. There might even be rationale to go up to 4.4g/kg.
What about Morton et al., 2018?
You may be familiar with an excellent meta-analysis on protein and resistance training (Morton 2018), which recommends 1.6g/kg/d for those looking to maximize FFM. I’m sure you may have also heard the 95% confidence interval was from 1.6–2.2g/kg/day. Here are the results:
Something that caught my eye when analyzing this data was there were only four studies with trained subjects:
This shows a large effect of protein intake on changes in FFM in trained subjects. The inclusion criteria were:
Any randomised controlled trials (RCTs) that combined a RET and protein supplement intervention were considered for this meta-analysis.
and the authors concluded
Protein supplementation is sufficient at ~1.6 g/kg/day in healthy adults during RET…... This analysis shows that dietary protein supplementation can be, if protein intake is less than 1.6 g protein/kg/day, both sufficient and necessary to optimise RET-induced changes in FFM and 1RM strength. However, performance of RET alone is the much more potent stimulus, accounting, at least according to this meta-analysis, for a substantially greater portion of the variance in RET-induced gains in muscle mass and strength.
While ideal for a meta-analysis, sport science research doesn’t have a lot of (gold-standard) RCTs, so a LOT of studies didn’t fit the criteria. In fact, you’ll notice that none of the studies included with trained participants were in a surplus.
4.2 Carbohydrates
Let’s move on to carbohydrates — something we know very little about in terms of muscle growth. We need carbohydrates for two main purposes when training:
- To maintain high glycogen levels to sustain muscle contractions during strength training sessions.
- To enhance muscle recovery and adaptation between sessions.
Carbohydrate manipulation, outside of extremes like that of a ketogenic diet, has not really been studied. For example, there’s no studies comparing hypertrophy outcomes between with 4g/kg of CHO versus 7g/kg of CHO. Therefore we don’t have much data to interpret.
One thing we can do is look at the observational data of physique athletes. This gives us some insight.
The range of carbohydrate intake in the literature is huge. There are a ton of studies that aren’t included too — these are just to give you an idea of the data. Practically, we have to consume enough carbohydrates to refill glycogen stores. Other than that we can look at the observational data and do a bit of rounding up from 3.9g/kg. I suggest a wide range of intake when bulking from 5–8g/kg. I’ll go into more detail of why it’s so high later.
4.3 Fats
Fat intake is similar to carbohydrate intake when it comes to research with resistance training. We just don’t have that much data comparing different intakes. We have observational studies and most sport nutrition guidelines suggest 20–30% of you calories should come from fat.
There are also some suggestions that low fat intake can lower testosterone, which is what I want to make the focus of this section.
If we look at data from Wang et al., we can see that switching from a 33% fat diet to a 13% fat diet had a statistically significant but probably not physiologically significant difference in total testosterone in subjects who were overweight, in a caloric deficit and between 50–63 years old. Thus, this study doesn’t give us a good picture of what would happen on a lower fat diet in a healthy young person who is resistance training and in a surplus.
Let’s look at one more study that is often cited when people mention low fat intake results in lower testosterone (Hamalainen et al., 1983). Male participants were transferred from their customary diet to an experimental diet for six weeks and there was a significant decrease in serum total testosterone concentrations. This decrease in testosterone was reversed when participants increased their fat intake again. The diets changed from of a baseline of 45% fat, to 25% fat, then to 37% fat. The participants were 30–49 year old men from Finland.
I’m not sure that these two studies give us a lot of support to suggest that low fat diets are necessarily worse. However, we do need to have fat in the diet for absorption of fat soluble vitamins and precursors such as vitamin A. There is some data to suggest it low levels can be cause decreases in HDL (reference guidelines). There is also a lot of cross sectional data that I didn’t include so that I can keep this post short(ish).
5. Summary & Recommendations
Now that we’ve covered a few studies and understand the data behind it — These are my current recommendations:
I think there is some rationale for having a higher protein intake than most people recommend if we look back at the Antonio studies, which is why my recommendations have a baseline protein intake of 2.2g/kg. For carbohydrate intake we need enough to recover, and as long as we are eating above the minimum fat intake I would be more inclined to consume carbs than fat. This leads me to my next topic:
5.1 Which macronutrients should we increase given the choice?
What if we’re within all of these ranges but still want to know what are the optimal macros for gaining minimal fat and maximizing muscle. We’re really going to extrapolate from the data here because there aren’t any studies (outside of extremes like keto) that compare overfeeding with carbs vs fat while resistance training. There are a number of them done in an overfeeding setting though. It revolves around the idea of carbohydrate oxidation.
Enter Horton et al., 1995
The goal of this study was to determine whether excess fat or carbohydrate leads to greater fat accumlation in sedentary, lean healthy subjects in a metabolic ward. Using a crossover design they overfed participants for 14 days with +50% of their maintenance calories of either fat or carbohydrates. They found that overfeeding with carbs produced increase carbohydrate oxidation and increased total energy expenditure so that less energy was stored as adipose tissue (70–75%) compared to overfeeding with dietary fat (90–95%). Ultimately, this study found that excess dietary fat intake leads to a greater accumulation of fat mass than excess carbohydrates.
Acheson et al studied the effect of carbohydrate overfeeding on glycogen storage capacity and de novo lipogenesis in a very small sample (3 males). Glycogen stores were first depleted by restricting energy intake from 2,000 to 1,360 kcal (10% CHO, 15% PRO, 75% FAT) and increased exercise over 3 days. This was followed by 7 days of carbohydrate overfeeding (86% CHO, 11% PRO, 3% FAT), providing 3,600 kcal on the first day and increasing to 5,000 kcal on the last day. Carbohydrate overfeeding was accompanied by an increase in carbohydrate oxidation and storage as glycogen. After 4 days of overfeeding, the glycogen stores were saturated and carbohydrate was converted to fat at the rate of 150g of lipid per 475 g carbohydrate per day. Fat oxidation was also suppressed, and an average net fat gain of 1.1 kg was reported (Acheson et al., 1988). This means that if glycogen stores are saturated we will still need to consume a very large amount of carbs to create new lipids. Accounting for the idea that we’re (hopefully) training at a volume to elicit growth, our extra carbs will help keep glycogen levels topped off.
In another small study (3 males), in a metabolic ward, it was shown that overfeeding with carbohydrates for 12 days increased body weight, but also increased energy expenditure and shifted substrate oxidation towards carbohydrates (Jebb et al., 1996).
Fat deposition under normal conditions is thought to occur mainly by deposition of dietary fat into adipose tissue. This process is energetically very efficient, with minimal loss of energy as heat. However, under conditions of high carbohydrate intake, de-novo lipogenesis can occur. This process is costly in terms of energy with a loss of some energy content of carbohydrate to heat.
Ultimately, increases in carbohydrate intake are buffered by increases in carbohydrate oxidation, even at carbohydrate excesses of up to roughly 30–50% of daily energy expenditure, before net de novo lipogenesis becomes physiologically important (Thyfault 2004, Siervo 2008, Jebb et al., 1996).
In a practical sense there may be a benefit from consuming higher carbohydrates because you may slightly increase energy expenditure; therefore, you could eat more total calories and ensure you have high levels of glycogen for training and recovery. The idea of calories in calories out (CICO) is still present and you will gain weight if eating in a surplus, some of which will be fat.
6. Rate of Gain
A factor that may be even more important than macronutrients (given you meet the threshold of protein intake) is rate of gain. How fast should we gain weight? Well, most studies are only 3–4 months so we have to extrapolate a lot.
It’s also difficult because a +500kcal surplus for someone on a 2200 kcal is very different than +500kcal surplus for someone who eats 3500. The former is a 23% surplus and the latter is a 14% surplus. Therefore, I like using percentages as they tend to scale better for individual guidelines.
We also have to consider that maintenance caloric requirements increase as body weight is gained during overfeeding — at about +2% increase per kg of weight gain — which isn’t much (Dallosso & James, 1984; Ravussin et al., 1985, Lammert et al., 2000).
I could re-analyze the data from the Garthe et al., 2013 and Ribeiro et al., 2019, but I don’t think that really helps much given the methods and participants — it’s also only two fairly small studies. From a practical sense, this is what I tell my athletes:
As we’ve seen, there might be rationale for having more of a surplus in the early stages of your training career. There’s also some merit in staying at maintenance and building mostly LBM. Yet, as we approach an advanced level of training we also approach our genetic ceiling of muscular potential. We can squeeze out a few extra pounds of muscle afterward — it just slows down a ton. Injuries can also set us back so focusing on staying healthy is very important. Further, if we are competing as physique athletes at an advanced level we probably aren’t gaining muscle during the competition season or 2–4 months afterwards until we return to baseline levels of hormones.
Further reading
I highly encourage you to dig into the primary research since there are more than 70 research studies published on overfeeding. A comprehensive list can be found at Sci-fit. I think one thing is evident from this dive into the literature. We need more research to determine the best way to bulk.
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FAQ
How do I track body weight?
I like to use different tracking methods for body weight depending on what I’m eating and how my body is reacting. For example,
