Table of Contents
At this point I’ve discussed:
- estimating your total daily energy expenditure (TDEE)
- setting a goal weight
- determining your caloric intake
- tracking your progress over time
- adjusting your calories accordingly
With this background knowledge it is now time to talk about actual nutrition. I will start with the three primary macronutrients: protein, carbohydrate, and fat. In this lesson I will go over protein.
Note: Alcohol is another macronutrient distinct from protein, carbohydrate, and fat. Fiber is sometimes considered a macronutrient but most consider it a subset of carbohydrates. I will discuss both of these in Lessons 8 & 7, respectively.
There are several benefits to consuming additional protein when attempting to lose weight:
- Protein intake stimulates muscle protein synthesis (“MPS”)(Jäger, 2017; Trommelen, 2019), which is crucial for skeletal muscle hypertrophy.
- This helps build new muscle or at least maintain current muscle while losing body fat (“BF”).
- Protein is more filling than carbohydrates and fats.(Dhillon, 2016) This is great for losing weight as most people prefer to minimize hunger during the process. On the other hand, for people who struggle to gain weight I recommend not increasing protein intake too high as this makes it difficult to consume additional calories.
- There is some evidence that above a certain threshold (around the levels described below) additional protein intake may not have further satiety benefits, at which point higher protein intake may be beneficial only to alleviate cravings.(Roberts, 2018)
- There is some evidence that above a certain threshold (around the levels described below) additional protein intake may not have further satiety benefits, at which point higher protein intake may be beneficial only to alleviate cravings.(Roberts, 2018)
- Protein has an increased thermic effect of feeding relative to carbohydrate and fat. This leads to less net calorie absorption.
- While more speculative, there are hypotheses (ie, the “protein leverage hypothesis” and the newer “protein efficiency theory”) that our body desires a certain minimum amount of protein, and if individuals consume less than this their appetite and hunger will increase.(Hall, 2019; Raubenheimer, 2019; El-Mallah, 2020; Saner, 2020) Then they will consume more food/drink to help achieve the minimum desired protein intake level. Again, this is more speculative in nature and while there is some supporting evidence more research is needed.
Example: The thermic effect of feeding reflects what percentage of calories consumed are required to digest and absorb the food you eat. As indicated in lesson 1 this is estimated to be up to 30% for protein in some situations. Suppose a person increases their protein intake by 100 grams daily. This equals 400 kcal assuming 4 kcal per gram of protein. 30% of this equals 120 kcal. Thus, their net caloric absorption increase may be closer to 280 kcal than 400 kcal.
How much protein should you consume?
This is a somewhat controversial topic as different lines of evidence lead to different recommendations.
Minimum for general health
Standard dietary guidelines suggest:
- 2-3 years old: 5-20% of one’s calories come from protein
- 4-18 years old: 10-30% of one’s calories come from protein
- ≥19 years old: 10-35% of one’s calories come from protein
The recommended dietary allowance (“RDA”) of protein intake in adults is 0.8 grams per kilogram (g/kg) body weight (“BW”) daily (0.36 grams per pound (g/lb)). Please note that this does not match the recommendation from the standard dietary guideline above (see further discussion below).
There are several lines of evidence that this may be too low for optimal health, particularly when exercising regularly. In youth the current recommendations do not account for physical activity, the method used to determine the RDA (which varies by age in youth) likely underestimates actual requirements, and it’s unclear if minimum recommendations should be based on “normal” growth or a potentially different “optimal” growth.(Moore, 2019; Hudson, 2021) Evidence in seniors suggests 1.2 g/kg daily(Phillips, 2016; Putra, 2021) may be a better target, and an argument has even been made for up to 1.6 g/kg daily.(Nunes, 2021) In healthy populations higher protein intakes have been found to have a small benefit on several cardiometabolic markers without detrimental effects.(Vogtschmidt, 2021) Higher protein intake in middle-aged individuals has been associated with greater grip strength and thus may help stave off sarcopenia.(Jun, 2021)
One caveat In the elderly is that any advice to increase protein intake must be balanced against the increased satiation effect. If aiming for a certain protein intake level does not allow for consumption of sufficient calories to prevent undesired weight loss then it may be necessary to lower the protein target.
Note: It is technically challenging to determine how much protein is actually needed, as most methods are known to underestimate or overestimate the true amount. If curious, for a good overview of the various techniques consider reading through section 4 of this review. It is written with children in mind but the information applies to adults as well.
Example: If a person weighs 80 kilograms (176 pounds), the RDA is 80 kilograms * 0.8 g/kg = 64 grams of protein daily. For the elderly, 80 * 1.2 = 96 grams of protein daily; this may yield better health outcomes.
Minimum to maximally stimulate muscle protein synthesis (“MPS”) and strength
A 2018 systematic review and meta-analysis (SR/MA) concluded that consuming up to 1.62 g/kg of BW (0.73 g/lb) daily when following a resistance training program increases lean body mass (“LBM”) acquisition.(Morton, 2018) There is individual variability; some may benefit from consuming more and many will do well with less (see figure below). A 2020 SR/MA looking at studies with and without resistance training found significant benefit to increasing protein intake for LBM gain up to 1.3 g/kg of BW (0.59 g/lb) daily, with diminishing results beyond this, while also finding resistance training augments the results.(Tagawa, 2020) A 2022 SR/MA found that when engaging in resistance training, older adults consuming 1.2-1.59 g/kg of BW daily and younger adults consuming 1.6 g/kg of BW daily saw benefits relative to a baseline intake of ~1.2 g/kg of BW daily.(Nunes, 2022)
Going slightly above this while actively losing weight may additionally benefit some individuals(Helms, 2017), but practically speaking the studies do not indicate this will be a very significant difference. Therefore, I do not recommend purposely aiming for protein intake much above 1.3-1.6 g/kg (0.59-0.73 g/lb) per day for the hope of additional benefit.
There is evidence(Schoenfeld, 2018) that 20g of high-quality (quality is discussed below) protein per meal may come close to maximizing MPS, at least in the acute setting (this threshold increases to 40g after whole body resistance exercise). A case can be made for slightly higher protein consumption in the last meal of the day prior to fasting overnight. Thus, eating regular meals with at least 20 grams of high-quality protein, with more in the last meal of the day, should come close to maximizing MPS.
Scaled for body weight, 0.25 g/kg of BW can come close to maximizing MPS after a meal in young men, and adding two standard deviations to this (to capture outliers) yields 0.4 g/kg.(Schoenfeld, 2018) Eating 4 meals of 0.4 g/kg body weight yields 1.6 g/kg per day, which as mentioned above is thought to maximize MPS when not in a caloric deficit.
Regarding maximizing strength gain potential, a 2022 SR/MA found that reaching a total protein intake of 1.3 and 1.5 g/kg per day yields maximal results when not engaging and when actively engaging in resistance training, respectively. A figure showing their results is shown below.(Tagawa, 2022)
Note: For individuals with significant obesity the recommended values above on a per BW basis will lead to excessive protein consumption. Physiologically, much of the excess weight with obesity is comprised of adipose tissue, with only a small proportion being increased skeletal muscle mass and other organ tissue. As adipose tissue uses less dietary protein relative to skeletal muscle and other organs, using the 1.3-1.6 g/kg BW target is unnecessary. In this instance sticking to the per meal recommendation of 20-40 grams of high-quality protein is likely more logical.
- If a person weighs 100 kg (220 lbs) then 100 kg * 1.3 g/kg = 130 grams of protein daily. Split up into 4 meals this equals 32 grams of protein per meal. This will likely be sufficient to maximize (or come very close to maximizing) MPS.
- If a person weighs 180 kg (397 lbs), then aiming closer to the high end of the 20-40 gram per meal recommendation will be more appropriate; thus, aiming for 30-40 grams of protein in 4 meals during the day should be sufficient.
Maximum to avoid health risks
Potential health risks of high protein diets are frequently cited. I will emphasize some of the more commonly cited concerns here.
A 2020 SR/MA found no association of total protein intake with all-cause, cardiovascular, or cancer mortality, though there was a possible reduced risk of all-cause and cardiovascular mortality with higher plant protein intake and a possible increased risk of cardiovascular mortality with higher animal protein intake.(Qi, 2020)
High protein diets can harm those with severe chronic kidney disease.(Rhee, 2018) If you have chronic kidney disease I suggest discussing appropriate levels of protein intake with your healthcare provider. There is currently no strong evidence that high protein diets will harm healthy kidneys.(Devries, 2018a)
However, we currently lack sufficiently long-term studies with high protein intakes to prove conclusively no kidney damage is done over a many year time span.(Marinaro, 2021) What has been seen is that higher protein intake can lead to glomerular hyperfiltration (a measure of kidney function) in people with healthy kidneys at baseline, and the concern is that over a longer period (ie, several years) this will “wear out” the kidneys and they will ultimately decline faster.(Ko, 2020; Cho, 2022) It is possible that long-term damage may be a risk only in a subset of the population that experiences acute glomerular hyperfiltration.(Jhee, 2020) Much more research is needed to confirm if this is a valid concern; if so then perhaps someday we will be able to test people to see if they are at higher risk of this occurring.
Negative impacts on bone health may be overstated and are likely mitigated with adequate vitamin D & calcium consumption as well as resistance training.(Antonio, 2018) Even without resistance training, there do not seem to be negative effects of higher protein intakes on bone health if calcium intake is adequate.(Rizzoli, 2021) While there is an association of higher protein intake and risk of developing type 2 diabetes or other cardiometabolic disease(Mittendorfer, 2020), particularly if excess calories are being consumed(Fappi, 2020), it is unclear how meaningful this is when consuming an overall healthy diet, exercising regularly, and maintaining a healthy BF percentage.
Note: Another consideration is confounding variables; several studies have found higher protein intakes from red & processed meat are associated with unhealthy lifestyle factors. This leads to associations with poor health.(Song, 2016; Shab-Bidar, 2018) Overall, more research is needed on the impact of high protein diets and general health. An effective compromise, and my general recommendation for those with a primary goal of optimizing health (and with baseline healthy kidney function), is to consume a higher protein diet (closer to the higher ranges of 1.6 g/kg daily or ≥30 grams per meal as mentioned above) while actively losing weight, and then decrease protein intake once the weight loss journey is complete and weight maintenance (or gain) is the goal (closer to 1.3 g/kg daily or ≥20 grams of high-quality protein per meal). Serious athletes & lifters may benefit from staying at the higher ranges.
Having said that, if you go to lower protein levels and find this is making it harder for you to maintain a healthy BW or quality of life (due to increased hunger or for some other reason), then increasing protein intake is reasonable as there is no conclusive evidence that higher levels will cause harm and in this situation the benefits likely outweigh the risks.
Example: In lieu of strong recommendations of a maximum intake, let’s reconsider the guidelines stated above. For adults the RDA of protein is 0.8 g/kg per day. The acceptable macronutrient distribution range (“AMDR”) is 10-35% of daily calories from protein. If an adult weighs 80 kilograms and consumes 2,500 kcals daily, then:
- 80 * 0.8 = 64 grams of protein daily to meet the RDA
- 2,500 * [10%-35% range] = 250-875 kcal. Assuming 4 kcal per gram of protein, this comes to 62-219 grams of protein daily
- If consuming 1.3-1.6 grams per kilogram daily, this would equal (80 * 1.3) to (80 * 1.6) = 104-128 grams of protein daily
- If simply aiming for 30-40 grams of protein in 3-4 meals, this equals 90-160 grams of protein daily
It should be clear that all of the protein recommendations discussed here are well within what is considered safe from the standard dietary guidelines. It is also interesting to note that there are several considerations regarding why the RDA may be too low and how this relates to the AMDR.(Wolfe, 2017)
What if we have someone who is dieting and only consuming 1,500 kcal/day? Well 35% of this would yield an upper limit of 131 grams of protein daily. This would still meet the 1.6 gram per kilogram goal for an 80 kilogram person, but would not quite meet a 40 gram 4x daily goal for somebody considerably heavier. In this situation it would be ok to go temporarily higher on the protein intake while eating a low calorie diet under medical supervision. If not dieting under medical supervision this points to the fact that people with severe obesity generally do not need to be on very low calorie diets to steadily lose weight; a 2,000 kcal/day diet (which would allow 40 grams protein 4x daily and be within the AMDR) would likely be more appropriate.
Additional considerations for the elderly
As mentioned above, some authors hypothesize that a higher amount of protein intake is beneficial for elderly individuals to maintain skeletal muscle mass, but at this point it is not yet clear if this has a truly significant effect long-term.(Nishimura, 2021) It was recently theorized this may be helpful to stave off sarcopenia.(Rogeri, 2022) In particular, greater protein intake may be more beneficial in the elderly experiencing frailty or sarcopenia if they also perform resistance training.(Kirwan, 2022) In this last review the authors provide an overview of the literature regarding strategies to prevent sarcopenia and summarize their findings in the figure below. To be clear, this is still speculative, as no trials have evaluated their proposed strategy in whole.
In this figure suggesting theoretical aspects of delaying or preventing sarcopenia, the authors indicate that an ideal protein intake may be 1.6-1.8 g/kg/d with up to 0.6 grams per meal, each with 5 grams of leucine, and 3 meals throughout the day. It would also be important to consume sufficient calories and engage in regular resistance training while decreasing sedentary activity, minimizing inflammation, and consuming a varied diet to help promote gut microbiome diversity. However, as mentioned above:
- It can be difficult for elderly individuals to consume 1.8 g/kg/d of protein and the increased satiety from this may lead to decreased caloric consumption overall.
- If there is any underlying kidney damage, which is more common in elderly individuals, this level of protein intake may be harmful.
- In the elderly, a very small study indicated that high protein intake (in the study they reached ~1.76 g/kg daily) may lead to overall net loss of protein compared to ~0.8 g/kg daily.(Højfeldt, 2020) This needs to be replicated and studied further but does give pause to the belief that “more is better”.
Thus, despite this hypothesis, for many elderly individuals it may be more prudent to provide supplemental leucine and less total protein; we’ll have to await studies testing this directly to determine if this is actually a viable strategy.
There are several considerations when discussing the quality of dietary protein. In general the quality of protein intake becomes more important when engaging in resistance training if the overall quantity of protein intake is on the lower side.(Morgan, 2021)
Note: I am discussing quality conceptually, but there are actual ranking systems of different proteins based upon to what degree they provide various amino acids. These include the PDCAAS (protein digestibility-corrected amino acid score) and the more recent and theoretically improved DIAAS (digestible indispensable amino acid score).
- The PDCAAS considers the amino acid content of a consumed food item and the amino acid content in fecal material, assuming the remainder is used by the body. However, it’s known this can be inaccurate:
- For example, some amino acids are metabolized by the gut microbiome and thus appear to be digested with the PDCAAS method even though they are not used by the body.
- The DIAAS compares the most limiting indispensable amino acid in a protein source and the amino acid content in end-ileal material (material at the end of the ileum (the last segment of the small intestine) is unlikely to be further absorbed). This is considered more accurate. However, this is difficult to sample in humans.
- This is frequently tested in pigs and researchers are still building up a catalogue of values for different food items.
With the exception of people with very restricted diets I do not believe the DIAAS is worth considering at this point when choosing individual sources of protein beyond the considerations described below. Over time it may become easier to use the DIAAS more practically and if so I will update this. Feel free to read through this link for further material on these topics.
There are 9 essential amino acids (building blocks of protein) that are required in our diet; assuming you eat a variety of foods it is generally not difficult to obtain sufficient quantities of each. Of these, the amino acid leucine is most strongly associated with MPS. It is unclear how much leucine is required to stimulate MPS fully in the context of consuming sufficient protein in your diet overall, and estimates range anywhere from 1-3 grams per meal (usually closer to 2.5 grams).(Jäger, 2017) There may be merit in specifically choosing sources of protein that are leucine-rich (typically animal-based sources) or supplementing leucine directly if following a lower protein diet for any reason. This has been studied in older adults (who typically consume lower amounts of protein and calories in general) with mixed results.(Devries, 2018b; Volpi, 2018; Putra, 2021) Below is a table indicating the amount of leucine in different food sources from a 2021 review discussing various aspects of nutrition on muscle protein turnover.
The 2020-2025 Dietary Guidelines for Americans lists different protein sources in ounce-equivalents; this helps standardize portion sizes between different types. However, this ignores the varying essential amino acid content between different sources and thus the ounce-equivalents do not seem metabolically equivalent.(Gwin, 2021; Park, 2021) This will not be a practically relevant distinction for most but it’s worth keeping in mind for individuals who are on a lower protein diet or with restricted food choices. The table below indicates how ounce-equivalents of different protein sources can have dramatically different quantities of essential amino acids.
Tip: I mentioned cronometer.com in a prior lesson; feel free to plug a typical day of eating into that website to see if you are deficient in any of the amino acids or leucine in particular. Of note, it is actually quite difficult to be deficient in essential amino acids unless you follow a very restrictive diet.
Speed of digestion
Another consideration is fast vs. slow digesting protein. Whey protein is faster digesting than casein protein, and likely due to that reason absorption of whey protein can increase MPS more than casein protein in the acute setting when consumed in isolation, while consuming casein protein prior to bed may be beneficial due to slower absorption throughout the night.(Jäger, 2017) However, when you eat mixed meals (meaning protein with fat as well as fiber) all digestion slows significantly relative to consuming whey protein in isolation. Thus, this distinction in rates of digestion is unlikely to significantly matter for the general population who is consuming food in meals as opposed to isolated nutrients.
Tip: Many individuals will not need to supplement protein powder (typically purchased as whey or casein) directly as it is generally not too difficult to obtain sufficient quantities of protein through diet alone. However, for those actively losing weight and thus eating relatively few calories, and for those who do not eat meat, supplementation may be helpful. There are many brands of protein out there, and some are lower quality than others (due to the addition of unnecessary ingredients, amino acid spiking where cheap amino acids such as glycine are over-represented in the mixture, or contamination).(da Costa, 2021) One brand with very reasonable prices and generally thought to be of high-quality is MyProtein, which can be purchased from https://us.myprotein.com/ or https://www.myprotein.com/, depending on your location. However, I cannot guarantee this is pure.
Regarding plant-based protein powders, soy is the most studied although others such as pea protein also show promise if consumed in sufficient quantities; more research on these other options needs to be done.(Putra, 2021)
As an aside regarding all supplements, for individuals who want to ensure they use supplements that have been tested to indicate they contain what they claim (as unlike prescription medications they are not well-regulated, at least in the USA), independent certification organizations include(Ulery, 2021):
- U.S. Pharmacopeia
- NSF International
while certifications that indicate a product has been tested for banned substances include(Ulery, 2021):
- Aegis Shield Certified
- Banned Substances Control Group (BSCG) Certified Drug Free
- Informed-Choice Certified
- NSF Certified for Sport
Note: it is important to recognize much of the literature regarding leucine, fast vs slow digesting protein, and supplements involve nutrients consumed in isolation. There are several studies in the literature indicating whole food sources have different effects than would be expected simply from the individual protein components.(Burd, 2019) While the above can be considered for general guidance, especially if you are consuming protein supplements, simply eating a generally healthy diet of whole food sources with sufficient protein will likely net the vast majority of the benefit that will be obtained from dietary protein. I believe any additional benefit from attempting to manipulate leucine intake and the speed of protein digestion will be relatively minor.
Amino acids from different protein sources have variable bioavailability (meaning what percentage of the consumed nutrients are actually absorbed). However, this is difficult to measure accurately.(Watford, 2018) Practically speaking, if you are consuming a variety of food sources I would not worry about this detail.
Source (plant vs animal)
Lastly, another consideration is plant vs animal sources of protein. In general the literature is favorable towards plant-based sources for overall health, with particularly negative outcomes seen with processed meat and to a lesser degree unprocessed red meat.(Song, 2016; Mariotti, 2019; Qi, 2020; Yeh, 2021) A 2020 SR/MA did find decreased risk of all-cause mortality with increased protein intake, but more significant associations were seen with plant protein than animal protein sources.(Naghshi, 2020) A 2021 substitution analysis of 6 prospective cohort studies in the US generally found a lower risk of mortality when substituting out protein sources including eggs, processed meat, unprocessed meat, and poultry for protein sources including nuts, whole grains, legumes, and fish (I realize fish is not a plant source).(Zhong, 2021) Some of these findings are likely due to residual confounding as alluded to above (with healthier lifestyles being associated with greater plant protein intake and less animal protein intake). Other considerations regarding meat specifically are discussed in Lesson 11.
When exercising regularly and working to build muscle, plant protein sources seem less optimal relative to animal protein sources due to decreased essential amino acid content (specifically leucine).(Kerksick, 2021) However, one study did show that when consuming 30 grams of either wheat protein or milk protein there were similar rates of muscle protein synthesis over the next several hours, despite the wheat protein providing only 1.8 grams of leucine compared to 2.4 grams in the milk.(Pinckaers, 2021) Additionally, there is also evidence suggesting when consuming at least 1.0 g/kg of protein daily there may not be that much of a meaningful influence long-term between predominantly plant and animal sources.(Lim, 2021) Thus, aiming for the higher ranges of protein intake suggested above is likely beneficial if the majority of your protein intake will come from plant sources, but for individuals who are not competitive athletes or attempting to maximize their lean body mass acquisition this is likely not something to be overly concerned about.
Protein distribution throughout the day
Studies generally show splitting protein into multiple meals throughout the day will better continuously stimulate MPS than only consuming 1-2 meals daily.(Jäger, 2017; Schoenfeld, 2018) A recent SR of studies that did not include resistance training found a small benefit to a more even distribution of protein intake throughout the day regarding LBM.(Jespersen, 2021) The more even distribution allowed more meals to meet the per meal protein recommendations listed above.
If consuming meals with a decent amount of protein (at the levels recommended above) several times throughout the day, the timing of protein intake with respect to the timing of a workout is less relevant, and protein supplementation peri-workout has not shown benefit relative to other times of day.(Wirth, 2020) Therefore, if consuming close to 1.3-1.6 grams of protein per kilogram of body weight daily divided in at least 3 meals, I do not believe there is any additional meaningful benefit to ensuring you consume protein directly before or after a workout. One exception here would be individuals who perform resistance training late in the evening; consuming protein after the workout in this instance may be helpful.(Antonio, 2020)
For individuals employing a time-restricted eating or intermittent fasting strategy (discussed in Lesson 12), I recommend consuming a decent amount of protein at the edges of the eating window.
General recommendations to maximize muscle protein synthesis
The above considerations regard health in addition to aiding skeletal muscle hypertrophy. For fitness- and physique-minded individuals who would like to maximize MPS with the goal of maximizing skeletal muscle hypertrophy, a 2021 review summarized much of the literature and summarized their recommendations in the below figure and table.
Protein intake is helpful for several reasons and attempting to aim for the minimum amounts recommended above, particularly when attempting to lose weight, can make the dieting process easier. As mentioned in prior lessons, maintaining LBM while losing BF is likely helpful to keep the weight off long term and consuming sufficient protein assists with this goal.
The jury is still out regarding very high protein intake over many years, but there are several lines of evidence indicating within the time frame of months to 1-2 years high protein intake is safe. While the RDA is 0.8 g/kg per day, this does not include considerations of resistance training which generate higher requirements, as well as other considerations.(Wolfe, 2017) I thus recommend individuals without health conditions such as chronic kidney disease to aim for at least 1.2 grams per kilogram per day on a regular basis while undergoing resistance training and increasing this further while dieting to lose weight.
Spreading this out throughout the day will likely be additionally helpful. Attempting to make the majority of this come from plant sources, fish, and unprocessed meat will likely aid overall health. It is also ok to eat more than this for satiety-inducing purposes or for personal preference, though it’s unclear if there may be negative consequences of higher intake if consumed over many years. For individuals who are not tracking calories regularly, you can track grams of protein every now and then to see if you are meeting these thresholds and if not then adjust your dietary intake accordingly.
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