Optimizing Dietary Protein

Dietary Strategies for Optimizing Skeletal Muscle Mass

Getting dietary protein into your muscle.

This starts in the mouth with chewing, continues in the stomach with the action of hydrochloric acid and pepsin, and concludes in the small intestine with further enzymatic activity from trypsin and chymotrypsin.  Under these mechanical and chemical influences, protein is reduced to amino acids, dipeptides, and tripeptides which are taken into cells lining the small intestine via active transport and then passed into the bloodstream.  In the bloodstream, these protein substrates are transported in their unbound form.  Upon arriving at a tissue actively synthesizing protein, these compounds are again actively transported from the bloodstream into cells, including muscle cells, where they are assembled into tension-developing structures called sarcomeres.

1. Is there a limit to how much protein can be absorbed from the GI tract in one meal?

The body can absorb nearly all ingested protein, regardless of the amount. However, muscle protein synthesis (MPS) that generates more contractile elements to produce more tension and potentially more muscle volume, appears to hit a maximum of 20–40 grams of uptake per meal, depending on body size and protein quality. Absorption and utilization are distinct: while your gut can absorb more than 30 grams, amino acids that are absorbed but not committed to MPS may be oxidized or used for other metabolic processes rather than sidetracked for muscle building.

The evidence for this plateau of MPS utilization of 20–40 grams per meal comes from studies using tracer methodologies to measure ingested amino acid incorporation into muscle tissue. One such study by Schoenfeld and Aragon (2018) concluded that ~0.4 g/kg/meal of high-quality protein—roughly 20–40 grams depending on body weight—is optimal for MPS in young adults. Beyond this, additional amino acids are more likely to be oxidized or used for other metabolic functions rather than further increasing MPS.  These studies are very challenging and the results are an absolute function of the experimental conditions, including the sampling duration. Hence, the findings about maximal incorporation could have been influenced by the timing of the muscle sampling.

Newer research speaks to just htis point. In a  2023 study published in Cell Reports Medicine, investigators ffound that ingesting 100 grams of protein post-exercise led to a greater and more sustained MPS response than 25 grams, suggesting that the anabolic response may not have a strict upper limit. The key difference between this and the Schoenfeld study lies in the duration of measurement—Schoenfeld tracked MPS for a few hours, potentially missing delayed effects from larger protein doses.

So, while the 20–40 gram guideline is still practical for most people aiming to optimize MPS across multiple meals, it’s not a hard cap, and more research is needed.. 

Schoenfeld 2018: https://rdcu.be/eu05l

Trommelen 2023: https://doi.org/10.1016/j.xcrm.2023.101324

2. How soon after exercise is amino acid muscle uptake detected, and how long does it last?

Amino acid uptake into muscle begins within 30 minutes post-exercise and can remain elevated for up to 24–48 hours, with the most pronounced effect in the first 3–5 hours. This window is often referred to as the “anabolic window,” during which muscle cells are more sensitive to amino acids and insulin, enhancing MPS.

3. What factors determine the rate of amino acid uptake in skeletal muscle?

Several key factors influence this rate:

• Insulin levels: Insulin promotes amino acid transport into muscle cells, especially when paired with carbohydrates.
• Exercise: Resistance training increases blood flow and transporter activity, enhancing uptake.
• Amino acid composition: Leucine, in particular, is a potent stimulator of MPS via the mTOR pathway.
• Muscle fiber type and metabolic state: Fast-twitch fibers and muscles in a catabolic state (e.g., post-exercise or fasting) show higher uptake.
• Age and training status: Younger and well-trained individuals often exhibit more efficient amino acid utilization.

4. What about Creatine?

• Is it degraded (hydrolyzed) by stomach acid? 
• No

• Is it broken down by proteolytic enzymes in the either the stomach or small intestine?

• No

• How and where is it absorbed?

• • It is moved from the lumen of the small intestine (not the stomach) into cells lining the small intestine using a specific active transport system and from there into the bloodstream where it travels unbound.
• What tissues use creatine for their metabolism?
  • All tissues in the human body depend on energy generation in cells that use a combination of ATP and Phosphocreatine to move energy from the mitochondria to organelles that use it for a variety of functions.  In nerves and the brain, the energy is essential to maintain cell membrane electrical gradients that support nerve signal condition.  In muscle, the chemical energy is used to power the contraction of muscle cells, collectively generating tension which is ultimately demonstrated as force production in the whole muscle.
• How does it get from the bloodstream into target tissue cells like muscle?
  • This movement is controlled by and dependent on a creatine-specific active transport system.

Other Questions I’ll Answer Soon!

• What factors control how much creatine is incorporated into the target tissue?

Your Maintaining Mass While Losing Weight:

The Why, What and How!​

Introduction: Weight loss drugs such as Semaglutide and Tirzepatide have allowed my patients to see more weight loss than in the past.   While the weight loss advantages of these medications is notable, there is a concern about loss of muscle mass (MM).  Let’s talk more about why this is important, how we can track it, and how we can preserve and even build muscle mass throughout the body remodeling these medications cause.

Why Is Muscle Mass Important? ​

Muscle Mass (MM) plays a crucial role in metabolic health, physical functioning, and overall quality of life. ​ You naturally loose about 5% of your MM per year, which can leave you dangerously weak in your more mature years.  This loss of MM is associated with a number of disease conditions and injuries.  Conversely, improvements in muscle mass are associated with better health.  That means our goal in weight loss should be not only weight loss but preservation or even increasing your muscle mass. ​ Preserving and enhancing your MM is worthwhile goal throughout your health journey, and particularly during periods of weight loss. ​

Measuring Muscle Mass: ​

There are several methods measuring MM, including body composition assessment (BCA) and strength assessment. ​ While BCA provides accurate measurements of adiposity, it does not directly measure MM. ​ Hand grip strength measurements have been recommended as a cost-effective and clinically relevant way to assess MM. ​ Additionally, sitting-rising tests or chair stand tests can be used to evaluate lower extremity strength. ​

Preserving Muscle Mass: ​

To preserve MM while taking weight loss drugs, it is crucial to follow these strategies: ​

1. Dietary Protein: ​ Consuming enough protein daily is essential for preserving MM. ​ Several studies and practical observations suggests that a high-protein diet, with intake greater than 1.5 grams of protein per kilogram of body weight per day (g/kg/d), is required for preservation and enhancement of MM. ​ This is often quite a bit more protein than is in your typical diet, so protein supplementation is often needed to reach this target. ​I have written about this in more detail here.  How do you calculate your target? For most patients seeking to lose weight and for those seeking increase MM, you can calculate your daily protein intake goal by multiplying your ideal body weight in kilograms by 1.5.  (Your body weight in kilograms is about half of your body weight in pounds). Ideal body weight can be calculated here.  Using this calculator, I recommend using the ideal body weight value from the Peterson formula.
2. Resistance Training: ​ Muscle exercise aimed at increasing muscle strength is called resistance training.  This type of training (as distinct from endurance training) is a powerful driver of maintaining and building MM.  Several studies indicate that the minimum amount of resistance exercise is twice a week, targeting all major muscle groups. ​ Each session should consist of 8-12 repetitions for each exercise and last for a total of 60 minutes per week. A popular strength program called “body pump” can be found at YMCA and other community exercise facilities and can even be done at home using your phone and a few light weights.  This exercise program works all major muscle groups.  When you are at home or at work and have access to a stairs, I recommend doing single step step-ups, 20 repetitions per leg, repeated in 3 sets, two times per week.  This exercise session can be completed in less time than a standard work break, but don’t forget to take your water bottle for a chance to boost your water intake during the workout.  Importantly, the handrail will provide a source of stability and no special equipment is needed for this exercise.  You will be shocked at how your leg strength increases with this exercise!
3. Monitoring and Assessing Progress: Regular monitoring of body composition and strength is helpful to track changes and adjust the weight loss plan accordingly.  In the Wellivery program, I aim for gradual weight loss so I am far less concerned about measuring changes in your body composition.  You will notice these changes yourself (waist and hip size, for example) and can report them to me.  I am more interested in ​ repeated assessment of muscle strength which reflects the effectiveness of your resistance training. ​ In the Wellivery program, I use the simple 1 minute timed sit-to-stand-test in which you count how many times you can go from sitting to standing in 60 sec.  This test can be done at home and as your legs get stronger, you will see the number of sit-to-stand transitions increase.

Conclusion:

While weight loss drugs offer new possibilities for achieving significant weight loss, it is crucial to prioritize the preservation of muscle mass and strength. Protein consumption and regular resistance training are key strategies to achieve this goal. ​ At Wellivery, these strategies are built into your weight loss plan and regular monitoring of strength is used to track your optimal outcome. ​

* As you know, excess body weight increases your chances of: heart disease, diabetes, and cancer.
* Studies show that medication, hospital and doctor costs are higher if you are overweight or obese.
* Good News! Small changes in your weight can pay off big in reducing your blood pressure, blood sugar, and cancer risk!
* Tirzepatide may be the medication-adjunct you have been waiting for!

* Wellivery brings you Tirzepatide that is affordable with physician supervision.

Make an appointment to start the change!

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