- In this blog article I discussed some scientific studies where the ideal daily protein intake was investigated. Presently, a daily intake of 1.6g/kg/day seems to be optimal for muscular hypertrophy. Taking more protein simply leads to a plateau in muscular hypertrophy – so more protein than the recommended amount does not lead to more gains.
- Most of these studies look at the effect of protein intake in untrained individuals. But what about experienced lifters?
- A few studies have looked at more experienced weightlifters. In these groups, higher daily protein intake of 2.2-2.4 g/kg/day was found to be more effective than a lower intake, but other factors (such as the composition of their diet as a whole) may also play an important part in this.
How much protein do you really need?
A common question that pops up amongst many lifters is: how much protein do I really need per day to build muscle? Well, it depends! A recent meta-analysis study by Morton et al. (2017) revealed that daily protein doses of approx 1.6g/kg/day were needed in order to maximise the muscular hypertrophy benefits from resistance-training. However, it was also observed that greater doses than 1.6g/kg/day of protein, led to no further gains in muscular growth, suggesting a potential threshold limit at around 1.6g/kg/day of protein. But, one of the major drawbacks of that this was that the majority of research conducted had been on those untrained. Unfortunately, very little data exists on the influence of protein intake in those who are highly trained. Nevertheless, It is likely that participants which have greater levels of resistance training experience, need more protein in order to stimulate further gains.
Morton et al. (2018). Figure shows the dose-dependent relationship between increases in fat free mass and total protein intake. The optimal range for healthy adults seems to be approx. 1.6g/kg/day. However, this is not a one size fits all. Some individuals might need even more depending on training experience and some, less. Ideally, a range of 1.6-2.2 should be considered, with individuals adopting the top end of this range in order to maximise muscular hypertrophy gains. An important point to make is that this data was collected from mainly studies conducted in UNTRAINED individuals. While 1.6g/kg/day might be optimal for this group, more studies in TRAINED individuals need to be conducted to see where the optimal limits of daily protein intake are for this population.
Vargas et al. (2018): High Protein Vs. Low Protein Intake In Aspiring Female Physique Athletes
For the majority of people looking to maximise muscular hypertrophy in response to a resistance-training program, 1.6g/kg/day of protein seems to be a solid recommendation. But, for most of the general population, the majority of people will be classed as novice trainers (those with little to no resistance-training experience). In this case, their daily protein intake requirements won’t need to be sky high. Given that the majority of studies have been done using untrained participants and 1.6g/kg/day of protein seems to be the sweet spot for maximising muscle growth in this population, we have a pretty good idea of what protein requirements we should be aiming for this group. However, little has been done to really investigate those with more resistance training experience and whether this group done really benefit from greater daily protein intakes.
A recent study conducted by Vargas et al. (2018) investigated the influence of high and low daily protein intakes in resistance-trained females on muscular growth. In fact, this study is interesting not only because it looks at those who are resistance-trained, but also because this is done in resistance-trained females. Most of the studies of the Morton et al. (2018) paper were actually conducted using male participants, and so females have tended to be under represented in these protein studies. The results of this study can be potentially useful for those resistance-trained females looking to implement daily protein intakes to maximise their muscular gains.
So, what was done in this study? Well, resistance-trained females were randomised to ingest either a low protein diet or a high protein diet in conjunction with a supervised 8 week resistance training program. The participants of the high-protein group consumed at least 2.4g/kg/day and those of the low protein group consumed at least 1.2g/kg/day. Participants were instructed to track all food intake but there were no limitations placed on daily carbohydrate or fat intake for either group (eek! Potential big limitation of the study!). At the end of the 8-week study, the high protein group exhibited significant gains in fat free mass than the low protein group. Another interesting finding was that the high protein group lost significantly more fat than the low protein group, even though the high protein group consumed on average more daily calories (approx. 400).
As suggested by Vargas et al. (2018) a few things could have attributed to this. Firstly, the thermic effect of food. Given that is takes more energy to digest protein (hence more calories lost as heat) than fat or carbohydrate, it is possible that the high protein group did exhibit a greater increase in the energy expenditure side of the energy balance equation (calories in and calories out). Moreover, it has been observed that overfeeding can lead to an increase in non-exercise activity thermogenesis (e.g. walking to work, typing fidgeting). The higher protein intake could have led to an increase in this, increasing calorie expenditure.
Vargas et al. (2018). Major limitation of the study was that total daily energy intake was not controlled for. The higher protein intake group did in fact consume approx. 400 daily calories more than the low protein group. It is likely that this greater overall energy intake contributed to the increased fat free mass gains observed in the higher protein intake group.
Looking at the results of this study, it seems that resistance-trained individuals can benefit from higher daily protein intakes. Given that the post-exercise muscle protein synthesis response to resistance-training seems to be attenuated in resistance-trained individuals, higher daily protein intakes are likely needed in this population to maximise protein synthesis. These higher daily protein intakes could then potentially maximise the post-training responses which set the muscular hypertrophy process in motion. In a recent study by Bandegan et al. (2017), it was observed that young resistance trained male bodybuilders (with greater than 3 years training experience) might have daily protein intake needs as high as 2.2g/kg/day. While more studies need to be conducted in resistance-trained individuals, it does seem likely that this population could benefit from much higher daily intakes than what is currently recommended.
Vargas et al. (2018). Figure shows the change in fat free mass after 8-weeks of resistance training in those resistance-trained females who consumed a daily high protein intake (at least 2.4g/kg/day) and those who consumed low daily protein intake (at least 1.2g/kg/day). IMPORTANRT: In both groups, their were no restrictions on daily carbohydrate or fat intake. As you can see, the changes in the high protein group were significant. Suggesting that higher protein intakes do lead to significant increases in fat free mass gains in response to resistance-training in resistance-trained individuals.
However, there are some important points to keep in mind when looking at these results. The biggest limitation was total daily calorie intake between the two groups. While daily protein intakes were controlled, carbohydrate and fat consumption was not and in fact, the total daily calorie intake of the higher protein group was larger than the lower protein group. It might not be surprising then why the higher protein group gained more muscle mass. This group simply ate more! Another consideration to keep in mind is the pre- and post-exercise protein intake. The high protein intake group was given 25g of protein both immediately pre- and post-workout, while the low protein intake group was given only 5g. Given that some research has suggested the idea of an anabolic-window of opportunity (increased muscle sensitivity to protein uptake), the higher pre- and post-workout protein of the high protein group, might have led to an increase in accretion of muscle proteins thus increasing the potential for more muscular hypertrophy gains.
Finally, the protein intake ranges selected for this study also proved as a limitation. For one, the range is pretty large! (0.9-2.4g/kg/day). More testing needs to be done to assess the influence of these higher protein intakes up to 2.4g/kg/day on body composition. Furthermore, given that a daily protein intake of approx. 1.6g/kg/day appears to be a point of optimality for most (Morton et al. 2017), it would be interesting to compare this with that of higher protein intakes (2.4g/kg/day) in resistance-trained individuals.
At present, more needs to be done to assess the influence of very high protein intakes on body composition in resistance-trained individuals. However, given the data at present, it does suggest that indeed, higher protein intakes (certainly above 1.6gkg/day) might lead to greater increases in fat free mass and fat loss in resistance-trained individuals. While 1.6g/kg/day seems to be a point of optimality for the majority of those looking to improve body composition, those who are highly trained, probably need more to truly maximise their gains. But, more needs to be done in order to really identify this upper end range for this population.