Lesson 4: Protein

Table of Contents


Introduction

At this point we’ve talked about:

  • metabolism
  • estimating our total daily energy expenditure (TDEE)
  • setting a goal weight
  • determining our caloric intake
  • tracking our progress over time
  • adjusting our calories accordingly

Now we are in a better position to talk about actual nutrition. We will start with the three primary macronutrients: protein, carbohydrate, and fat. In this lesson we 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 three primary 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 carbohydrate and fat.(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)
  • Protein has an increased thermic effect of feeding relative to carbohydrate and fat. This leads to less net calorie absorption.

Example: The thermic effect of feeding reflects what percentage of calories consumed are required to digest and absorb the food we 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 we 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 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(Phillips, 2016), especially in seniors where 1.2 g/kg may be a better target. In the elderly this must be balanced against the increased satiation effect; if aiming for a certain protein target does not allow for intake of sufficient calories to prevent undesired weight loss then it may be necessary to lower the protein target.

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”)

Recently, a systematic review and meta-analysis (SR/MA) concluded 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). An even more recent SR/MA looking at studies with and without resistance training finds 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) 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.

This figure shows how changes in lean body mass change with different levels of protein intake
This figure reproduced from (Morton, 2018) depicts segmental linear regression of the change in fat free mass (y axis) against the average protein g/kg per day ("g/kg/d") intake (x axis) in resistance training study populations (each circle is a separate study). They find a breakpoint at 1.62 g/kg/d, with a wide confidence interval that doesn't quite reach statistical significance (p = 0.079), implying many people can do well with less than 1.6 g/kg/d intake.

There is evidence(Schoenfeld, 2018) that 20g of high quality (quality is discussed below) protein per meal (up to 40g after whole body resistance exercise) may come close to maximizing MPS, at least in the acute setting. 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.

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.

Example:

  • 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. Some of the most common concerns include kidney health, bone health, and development of diabetes. High protein diets can harm those with severe chronic kidney disease.(Rhee, 2018) 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. Negative impacts on bone health may be overstated and are likely mitigated with adequate vitamin D & calcium consumption as well as resistance training.(Pedersen, 2013; Antonio, 2018) While there is an association of higher protein intake and risk of developing type 2 diabetes(Mittendorfer, 2020), it is unclear how meaningful this is when consuming an overall healthy diet, exercising regularly, and maintaining a healthy body fat percentage.

In the elderly, one recent 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. This needs to be replicated and studied further but does give pause to the belief that “more is better”.(Højfeldt, 2020) This does not refute the recommendation of aiming for 1.2 g/kg in the elderly listed above (as this level of intake was not studied here), it just indicates going well above 1.2 g/kg may do more harm than good.

Note: Another consideration is confounding; 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, 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.


Protein quality

There are several considerations when discussing the quality of dietary protein.


Amino acids

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 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 relatively lower amount of protein and calories in general) with mixed results.(Devries, 2018b; Volpi, 2018)

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 following 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 moreso than casein protein in the acute setting when consumed in isolation, while consuming casein protein prior to bed may be beneficial due to a slower absorption throughout the night.(Jäger, 2017) However, when we eat mixed meals (meaning protein with fat as well as fiber) all digestion slows significantly relative to consuming whey protein in isolation, and 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 addition of unnecessary ingredients or amino acid spiking where cheap amino acids such as glycine are over-represented in the mixture). 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.

Note: it is important to recognize much of the literature regarding leucine and fast vs slow digesting protein 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 one is 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 additional benefit of attempting to manipulate leucine and speed of protein digestion will be relatively minor.


Bioavailability

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 one is 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, with particularly negative outcomes seen with processed meat and to a lesser degree unprocessed red meat.(Song, 2016; Mariotti, 2019) Part of this is likely residual confounding alluded to above, but at the same time it is likely safest to minimize processed meat consumption and to limit red meat consumption if possible. This is discussed further in Lesson 10.

                           


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) If doing this, timing of protein intake with respect to the timing of a workout is less relevant, and protein supplementation periworkout 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 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. For individuals employing a time-restricted feeding or intermittent fasting strategy (discussed in Lesson 11), I recommend consuming a decent amount of protein at the edges of the eating window.



Conclusion

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 very helpful to keep the weight off long term, and consuming sufficient protein makes this easier.

The jury is still out regarding very high protein intakes 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. 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 dietary intake accordingly.

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References

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