Insulin sensitivity tends to decline with age in both men and women, but there are some gender-specific patterns and factors that contribute to differences in insulin sensitivity as individuals age. Here are some key considerations:

1. Hormonal Changes:
   • In women, the decline in estrogen levels during menopause is associated with changes in body composition and insulin sensitivity. Postmenopausal women may experience an increase in visceral fat and a decline in insulin sensitivity. Hormonal fluctuations throughout the menstrual cycle can also influence insulin sensitivity in premenopausal women.
2. Body Composition:
   • Changes in body composition, including an increase in body fat and a decrease in lean muscle mass, are common as people age. Both men and women may experience these changes, but the distribution of fat can differ between genders. Men tend to accumulate fat in the abdominal area, which is associated with a higher risk of insulin resistance and metabolic complications.
3. Muscle Mass:
   • Muscle mass plays a crucial role in glucose metabolism, and age-related loss of muscle mass (sarcopenia) is associated with decreased insulin sensitivity. Men typically have more muscle mass than women, but both genders can experience a decline in muscle mass with aging.
4. Physical Activity:
   • Physical activity levels can influence insulin sensitivity. Both men and women can benefit from regular exercise to help maintain or improve insulin sensitivity. However, adherence to exercise routines may vary between genders and can influence age-related changes in insulin sensitivity.
5. Inflammatory Factors:
   • Chronic low-grade inflammation, often associated with aging, can contribute to insulin resistance. Inflammatory markers may differ between men and women, and these differences can influence insulin sensitivity.
6. Adipose Tissue Distribution:
   • The distribution of adipose tissue (fat) can affect insulin sensitivity. Women tend to store fat subcutaneously (under the skin), while men may accumulate more visceral fat (around internal organs) with age. Visceral fat is more metabolically active and can contribute to insulin resistance.
7. Genetic Factors:
   • Genetic factors can contribute to individual differences in insulin sensitivity. While genetic predispositions can influence both men and women, the expression of certain genes may vary between genders.

It’s important to note that individual responses to aging and changes in insulin sensitivity can vary widely. Lifestyle factors such as diet, physical activity, and overall health play significant roles in mitigating age-related declines in insulin sensitivity. Regular health check-ups and screenings for conditions like diabetes are important for managing metabolic health as individuals age.

As always, individuals concerned about their insulin sensitivity or overall metabolic health should consult with healthcare professionals for personalized advice and recommendations.

Resting Metabolic Rate (RMR) is a measure of the number of calories the body requires at rest to maintain basic physiological functions, such as maintaining body temperature, supporting organ function, and other essential processes.

The estimation of RMR is based on the principle of indirect calorimetry, which involves the measurement of oxygen consumption (VO2) and carbon dioxide production (VCO2) during a period of rest.

The basic idea behind the calculation is to understand the respiratory exchange that occurs during metabolism.

Different macronutrients (carbohydrates, fats, proteins) are metabolized with distinct oxygen and carbon dioxide exchange ratios.

The respiratory exchange ratio (RER) is the ratio of carbon dioxide produced (VCO2) to oxygen consumed (VO2), and it varies depending on the type of fuel being metabolized:

RER = VO2/VCO2​

For carbohydrates: $RER\approx 1.0$

For fats: ≈ 0.7 RER ≈ 0.7

For proteins, it can vary but is typically between the values for carbohydrates and fats.

Now, to estimate the Resting Metabolic Rate (RMR), the amount of oxygen consumed is related to the calories burned. The basic formula is:

$RMR(incalories/day)=VO2(inliters/min)\times EnergyEquivalentforOxygen$

The energy equivalent for oxygen is the amount of energy (in calories) produced when one liter of oxygen is consumed. This value can vary slightly depending on the source, but a commonly used value is around 5 calories per liter of oxygen.

So, the formula can be expressed as:

$RMR=VO2\times 5$

In practice, the PNOE Metabolism Analyzer and similar devices use sophisticated algorithms and calibration procedures to convert the measured oxygen consumption into an estimate of Resting Metabolic Rate.

These algorithms take into account factors such as the respiratory exchange ratio, individual characteristics, and sometimes additional physiological parameters to improve the accuracy of the estimation.

It’s important to note that while RMR provides a baseline for calorie expenditure at rest, total daily energy expenditure (TDEE) would include additional calories burned through physical activity and the thermic effect of food.

RMR, however, forms a crucial component in understanding an individual’s overall energy needs.

What is TDEE and how is it determined?

Total Daily Energy Expenditure (TDEE) represents the total number of calories an individual burns in a day, taking into account all activities, including basal metabolic rate (BMR) or resting metabolic rate (RMR), physical activity, and the thermic effect of food (TEF).

Determining TDEE is essential for understanding an individual’s overall energy needs and is crucial for designing personalized nutrition and fitness plans.

Here’s a breakdown of the components that make up TDEE:

1. Basal Metabolic Rate (BMR) or Resting Metabolic Rate (RMR): This is the number of calories the body needs at rest to maintain basic physiological functions. It includes functions such as maintaining body temperature, supporting organ function, and other essential processes. As mentioned earlier, devices like the PNOE Metabolism Analyzer can measure RMR through breath analysis.
2. Physical Activity: This component includes all forms of physical activity, from intentional exercise to everyday movements (e.g., walking, climbing stairs). The more active a person is, the higher their energy expenditure from physical activity.
3. Thermic Effect of Food (TEF): This is the energy expended during the digestion, absorption, and metabolism of food. Different macronutrients (carbohydrates, fats, proteins) require varying amounts of energy for digestion and utilization. On average, TEF contributes to about 10% of TDEE.

The formula for TDEE is:

$TDEE=BMR/RMR+PhysicalActivity+TEF$

In practice, determining TDEE involves a combination of methods, including:

• Measuring BMR/RMR: This can be done through indirect calorimetry, as with devices like the PNOE Metabolism Analyzer, or through predictive equations that take into account factors such as age, sex, weight, and height.
• Estimating Physical Activity: This often involves using activity trackers, exercise logs, or self-reported activity levels. Various activity levels, ranging from sedentary to highly active, are assigned corresponding multiplier values to estimate the additional calories burned through physical activity.
• Accounting for TEF: This is typically a fixed percentage of the total caloric intake for the day, based on the macronutrient composition of the diet.

Once these components are determined or estimated, they are added together to calculate TDEE. Once TDEE is known, individuals can better understand their energy balance, helping them adjust their calorie intake to meet specific goals, whether it be weight maintenance, weight loss, or muscle gain. It’s important to note that TDEE is a dynamic value that can change based on factors like weight, age, and changes in physical activity levels. Regular reassessment is often recommended for accurate planning.

How can you improve your TDEE?

Total Daily Energy Expenditure (TDEE) is influenced by several factors, including basal metabolic rate (BMR), physical activity, and the thermic effect of food (TEF). Improving TDEE involves strategies to positively impact these components. Here are some ways to potentially enhance TDEE:

1. Increase Physical Activity:
   • Regular Exercise: Engage in regular physical activity, including both cardiovascular exercises (e.g., running, cycling) and resistance training (e.g., weight lifting). This not only burns calories during the activity but can also increase overall muscle mass, which contributes to a higher BMR.
   • Incorporate NEAT (Non-Exercise Activity Thermogenesis): Increase daily movement through activities like walking, taking the stairs, and incorporating movement into daily tasks. These activities contribute to TDEE without structured exercise.
2. Build Lean Muscle Mass:
   • Strength Training: Resistance training, such as weight lifting, helps build and maintain lean muscle mass. Muscle tissue is metabolically active, meaning it requires more energy at rest compared to fat tissue. Therefore, having more muscle can increase your BMR.
3. Stay Active Throughout the Day:
   • Break Up Sitting Time: Avoid prolonged periods of sitting. Take breaks to stand, stretch, or walk throughout the day. This contributes to NEAT and helps burn additional calories.
4. Optimize Nutrition:
   • Balanced Diet: Consume a well-balanced diet that includes an appropriate mix of carbohydrates, fats, and proteins. The body expends energy in digesting and metabolizing these nutrients, contributing to the TEF.
   • Consider Meal Timing: Some research suggests that spreading meals throughout the day (small, frequent meals) might increase TEF compared to fewer, larger meals.
5. Get Adequate Sleep:
   • Quality Sleep: Lack of sleep can negatively impact metabolism and energy expenditure. Aim for 7-9 hours of quality sleep per night to support overall health and well-being.
6. Stay Hydrated:
   • Water Intake: Staying well-hydrated is essential for various physiological processes, including metabolism. Drinking water can also contribute to a small increase in energy expenditure.
7. Be Mindful of Stress:
   • Manage Stress: Chronic stress can affect metabolism. Practices such as mindfulness, meditation, and relaxation techniques may help manage stress levels and support metabolic health.
8. Gradual Caloric Increases:
   • Avoid Extreme Diets: Very low-calorie diets can lead to a reduction in BMR as the body adapts to conserve energy. Gradual caloric increases, particularly when increasing physical activity, can be more sustainable.

It’s important to note that individual responses to these strategies can vary. It’s advisable to make changes gradually and consider consulting with a healthcare professional or a registered dietitian, especially if you have specific health concerns or goals. Additionally, monitoring progress over time and adjusting strategies based on individual responses is key to optimizing TDEE.

How does your THYROID health impact your metabolism?

Test and not GUESS your thyroid health in FUNCTIONAL lab ranges, not the “normal” ranges your doctor looks at …

Then look at the WHOLE picture and PATTERNS of type of thyroid dysfunction.

The thyroid panel is a group of blood tests that assess the function of the thyroid gland, which plays a crucial role in regulating metabolism. The thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), produced by the thyroid gland, have a direct impact on the resting metabolic rate (RMR).

Here’s how the thyroid panel results can influence RMR:

1. Thyroid Hormones (T3 and T4):
   • T4 (Thyroxine): T4 is the main hormone produced by the thyroid gland.
     • It is considered a prohormone because it is converted into the more active T3 form.
     • T4 levels are often measured in the thyroid panel.
   • If T4 levels are low, it can indicate hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones.
     • This can lead to a decrease in RMR.
   • T3 (Triiodothyronine):
     • T3 is the more active form of thyroid hormone.
     • It is responsible for many metabolic processes in the body, including regulating the RMR.
     • Low T3 levels may also be associated with hypothyroidism and can contribute to a reduced metabolic rate.
2. Thyroid Stimulating Hormone (TSH):
   • TSH is produced by the pituitary gland and stimulates the thyroid gland to produce T4.
   • Elevated TSH levels may indicate an underactive thyroid (hypothyroidism), suggesting that the body is trying to stimulate the thyroid to produce more hormones to meet metabolic demands.
3. Reverse T3 (rT3):
   • Reverse T3 is an inactive form of T3. In certain conditions, the body may convert T4 into reverse T3 instead of the active T3 form.
   • Elevated levels of reverse T3 can be associated with a lower metabolic rate.
4. Thyroid Antibodies:
   • Tests for thyroid antibodies, such as anti-thyroid peroxidase (TPO) antibodies, are often done to assess autoimmune thyroid conditions like Hashimoto’s thyroiditis.
   • These conditions can affect thyroid function and potentially impact metabolic rate.

In summary, an imbalance in thyroid hormones, whether it’s hypothyroidism (low thyroid hormone levels) or other thyroid disorders, can lead to changes in resting metabolic rate. A lower metabolic rate may result in symptoms such as fatigue, weight gain, and intolerance to cold. It’s important to note that individual responses can vary, and other factors also contribute to metabolic rate, such as age, gender, muscle mass, and overall health. If you have concerns about your thyroid function and metabolic rate, it’s recommended to consult with a healthcare professional for a thorough evaluation and appropriate management.

The PNOE Metabolic Analyzer is a device used for metabolic testing, including the measurement of resting metabolic rate (RMR). RMR is the amount of energy expended by the body at rest to maintain basic physiological functions. While the PNOE Metabolic Analyzer primarily measures respiratory gases to estimate energy expenditure, it doesn’t directly measure thyroid hormones. However, there are certain patterns in metabolic data that may be indicative of low thyroid function when analyzed in conjunction with other clinical information.

Here’s how a low resting metabolic rate measured by a PNOE Metabolic Analyzer could potentially correlate with low thyroid function:

1. Low RMR and Hypothyroidism:
   • Hypothyroidism is characterized by an underactive thyroid gland, leading to reduced production of thyroid hormones (T3 and T4). Thyroid hormones play a crucial role in regulating metabolism. When thyroid function is low, it can result in a decrease in the body’s overall energy expenditure, contributing to a lower resting metabolic rate.
2. Analysis of Respiratory Gas Exchange:
   • The PNOE Metabolic Analyzer measures respiratory gases (oxygen consumption and carbon dioxide production) during rest. Thyroid hormones influence cellular respiration, and a deficiency in these hormones can affect the efficiency of oxygen utilization and carbon dioxide production. An analysis of these gases may provide insights into metabolic function.
3. Clinical Correlation:
   • While the PNOE Metabolic Analyzer provides valuable metabolic data, it’s important to interpret the results in the context of the individual’s overall health and clinical history. Low RMR alone is not conclusive evidence of thyroid dysfunction, as other factors, such as age, body composition, and overall health, can influence metabolic rate.
4. Comprehensive Thyroid Panel:
   • To confirm or rule out thyroid dysfunction, a comprehensive thyroid panel, including measurements of TSH, T3, T4, and possibly thyroid antibodies, is typically performed. Elevated TSH and/or low T3 and T4 levels are indicative of hypothyroidism.
5. Consultation with a Healthcare Professional:
   • Interpreting metabolic data and correlating it with thyroid function requires expertise. A healthcare professional, such as an endocrinologist or a healthcare provider familiar with metabolic testing, can help analyze the results in the broader context of the patient’s health and order additional diagnostic tests if necessary.

It’s essential to note that while a lower RMR may be associated with hypothyroidism, other factors can contribute to variations in metabolic rate. Therefore, a comprehensive evaluation, including clinical history, physical examination, and laboratory tests, is crucial for an accurate diagnosis and appropriate management. If you have concerns about your metabolic rate or thyroid function, it’s advisable to consult with a healthcare professional for personalized guidance and interpretation of test results.

How does Muscle health impact your Resting Metabolism?

Muscle health, muscle protein synthesis (MPS), and resistance training play significant roles in improving resting metabolism. Resting metabolism, also known as Resting Metabolic Rate (RMR) or Basal Metabolic Rate (BMR), represents the number of calories the body needs at rest to maintain basic physiological functions. Here’s how muscle-related factors contribute to an enhanced resting metabolism:

1. Increased Muscle Mass and Basal Metabolic Rate (BMR):
   • Metabolically Active Tissue: Muscle tissue is metabolically active, meaning it requires energy (calories) to maintain itself even at rest. Therefore, individuals with a higher percentage of lean muscle mass tend to have a higher BMR. Resistance training stimulates the growth and maintenance of muscle tissue, leading to an increase in the metabolically active component of the body.
2. Muscle Protein Synthesis (MPS) and Energy Expenditure:
   • Energy Cost of Protein Synthesis: Muscle protein synthesis is the process by which the body builds and repairs muscle proteins. This process requires energy, contributing to overall energy expenditure. After resistance training, the body engages in MPS to repair and rebuild muscle fibers, leading to an increased calorie burn during the post-exercise recovery period.
3. Afterburn Effect (Excess Post-Exercise Oxygen Consumption – EPOC):
   • Increased Metabolic Rate Post-Exercise: Intense resistance training can lead to an afterburn effect, also known as Excess Post-Exercise Oxygen Consumption (EPOC). After a workout, the body continues to consume oxygen and expend energy to restore physiological functions and repair tissues, including muscle. This post-exercise elevation in metabolism contributes to an extended period of increased calorie expenditure.
4. Insulin Sensitivity and Nutrient Partitioning:
   • Improved Insulin Sensitivity: Resistance training has been shown to improve insulin sensitivity. Enhanced insulin sensitivity helps the body manage glucose more effectively, influencing how nutrients, especially carbohydrates, are utilized for energy. Improved nutrient partitioning can contribute to better metabolic health and energy utilization.
5. Prevention of Age-Related Muscle Loss (Sarcopenia):
   • Mitigating Muscle Loss with Age: As individuals age, there is a natural tendency to lose muscle mass, a condition known as sarcopenia. Engaging in regular resistance training helps mitigate age-related muscle loss, preserving lean muscle mass and supporting a higher BMR throughout the lifespan.
6. Long-Term Metabolic Adaptations:
   • Positive Changes in Body Composition: Resistance training, when combined with proper nutrition, can lead to positive changes in body composition, such as increased muscle mass and decreased body fat. These changes contribute to an improved metabolic profile over the long term.

It’s important to note that the impact of resistance training on resting metabolism can vary among individuals, and results depend on factors such as the intensity and frequency of training, individual response, and overall health.

To maximize the benefits, it’s advisable to incorporate a well-designed resistance training program and to consider consulting with a fitness professional or healthcare provider for personalized guidance.

Additionally, proper nutrition, including sufficient protein intake, is crucial to support muscle health and protein synthesis.

Muscle protein synthesis (MPS) is the process by which the body builds new muscle proteins to repair and replace damaged or worn-out muscle tissues. It is a crucial aspect of muscle adaptation to various stimuli, including exercise and resistance training. MPS involves the incorporation of amino acids into muscle proteins, resulting in an increase in muscle mass and strength.

Muscle protein synthesis (MPS) is the process by which cells build new proteins, specifically within muscle tissue. In the context of exercise and nutrition, it is a crucial mechanism for muscle growth and repair. When you engage in resistance training or consume protein-rich meals, it stimulates muscle protein synthesis, leading to an increase in muscle protein.

Leucine is one of the essential amino acids, and it has been recognized as a key player in promoting muscle protein synthesis. Dr. Donald Layman, a prominent researcher in the field of nutrition and protein metabolism, has conducted studies examining the role of leucine in muscle protein synthesis.

The leucine threshold concept suggests that there is a specific threshold or level of leucine intake that is required to maximally stimulate muscle protein synthesis. Leucine is unique among the amino acids in its ability to activate a signaling pathway called the mammalian target of rapamycin (mTOR), which is a central regulator of muscle protein synthesis. The idea is that reaching a certain level of leucine in the blood is necessary to fully activate mTOR and, consequently, maximize the muscle protein synthesis response.

Research by Dr. Layman and others has explored the optimal amount of leucine needed to stimulate muscle protein synthesis, and this has implications for dietary recommendations, particularly for individuals involved in resistance training or seeking to optimize muscle growth and maintenance.

It’s important to note that while leucine is a crucial amino acid for muscle protein synthesis, overall protein intake and the balance of all essential amino acids in the diet also play important roles in supporting muscle health and development. The leucine threshold concept is just one aspect of the broader understanding of protein metabolism and muscle physiology.

Here’s an overview of the key concepts related to muscle protein synthesis:

1. Amino Acids and Protein Synthesis:
   • Amino acids are the building blocks of proteins, and they play a central role in muscle protein synthesis.
   • There are 20 different amino acids that can combine in various sequences to form proteins. Nine of these amino acids are considered essential, meaning the body cannot produce them and must obtain them through the diet.
2. Essential Amino Acids (EAAs):
   • EAAs are particularly important for muscle protein synthesis because the body cannot synthesize them on its own.
   • The nine essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
   • Among these, leucine is often considered the most critical for initiating muscle protein synthesis.
3. Leucine and Muscle Protein Synthesis:
   • Leucine is an essential amino acid that serves as a key regulator of muscle protein synthesis. It activates a pathway called the mTOR (mammalian target of rapamycin) pathway, which signals the body to build new proteins.
   • Leucine-rich sources include animal products such as meat, dairy, and eggs.
4. Protein Timing and Distribution:
   • Protein consumption around the time of exercise, especially post-exercise, is important for maximizing muscle protein synthesis. Consuming a protein-rich meal or supplement containing essential amino acids, particularly leucine, can support this process.
   • It’s generally recommended to distribute protein intake evenly throughout the day to provide a steady supply of amino acids for muscle protein synthesis.
5. Protein Quality and Source:
   • The quality of protein sources is determined by the amino acid profile and digestibility. Animal-based proteins such as meat, poultry, fish, eggs, and dairy are considered high-quality sources of protein because they contain all essential amino acids in the right proportions.
   • Plant-based protein sources can be combined to ensure a complete amino acid profile. For example, combining legumes with grains or nuts can create a complementary amino acid profile.
6. Protein Quantity:
   • Meeting daily protein requirements is crucial for supporting muscle protein synthesis. The optimal amount of protein can vary based on factors such as age, activity level, and training goals. However, a general recommendation for individuals engaging in resistance training is to consume approximately 1.6 to 2.2 grams of protein per kilogram of body weight per day.

In summary, muscle protein synthesis is the process of building new muscle proteins, and it relies on the availability of essential amino acids, particularly leucine. Consuming an adequate amount of high-quality protein, whether from animal or plant sources, and distributing protein intake throughout the day can support muscle protein synthesis and contribute to muscle growth and repair.

Resting metabolism, also known as Resting Metabolic Rate (RMR) or Basal Metabolic Rate (BMR), represents the number of calories the body needs at rest to maintain basic physiological functions.

Here’s how muscle-related factors contribute to an enhanced resting metabolism:

1. Increased Muscle Mass and Basal Metabolic Rate (BMR):
   • Metabolically Active Tissue: Muscle tissue is metabolically active, meaning it requires energy (calories) to maintain itself even at rest. Therefore, individuals with a higher percentage of lean muscle mass tend to have a higher BMR. Resistance training stimulates the growth and maintenance of muscle tissue, leading to an increase in the metabolically active component of the body.
2. Muscle Protein Synthesis (MPS) and Energy Expenditure:
   • Energy Cost of Protein Synthesis: Muscle protein synthesis is the process by which the body builds and repairs muscle proteins. This process requires energy, contributing to overall energy expenditure. After resistance training, the body engages in MPS to repair and rebuild muscle fibers, leading to an increased calorie burn during the post-exercise recovery period.
3. Afterburn Effect (Excess Post-Exercise Oxygen Consumption – EPOC):
   • Increased Metabolic Rate Post-Exercise: Intense resistance training can lead to an afterburn effect, also known as Excess Post-Exercise Oxygen Consumption (EPOC). After a workout, the body continues to consume oxygen and expend energy to restore physiological functions and repair tissues, including muscle. This post-exercise elevation in metabolism contributes to an extended period of increased calorie expenditure.
4. Insulin Sensitivity and Nutrient Partitioning:
   • Improved Insulin Sensitivity: Resistance training has been shown to improve insulin sensitivity. Enhanced insulin sensitivity helps the body manage glucose more effectively, influencing how nutrients, especially carbohydrates, are utilized for energy. Improved nutrient partitioning can contribute to better metabolic health and energy utilization.
5. Prevention of Age-Related Muscle Loss (Sarcopenia):
   • Mitigating Muscle Loss with Age: As individuals age, there is a natural tendency to lose muscle mass, a condition known as sarcopenia. Engaging in regular resistance training helps mitigate age-related muscle loss, preserving lean muscle mass and supporting a higher BMR throughout the lifespan.
6. Long-Term Metabolic Adaptations:
   • Positive Changes in Body Composition: Resistance training, when combined with proper nutrition, can lead to positive changes in body composition, such as increased muscle mass and decreased body fat. These changes contribute to an improved metabolic profile over the long term.

It’s important to note that the impact of resistance training on resting metabolism can vary among individuals, and results depend on factors such as the intensity and frequency of training, individual response, and overall health. To maximize the benefits, it’s advisable to incorporate a well-designed resistance training program and to consider consulting with a fitness professional or healthcare provider for personalized guidance. Additionally, proper nutrition, including sufficient protein intake, is crucial to support muscle health and protein synthesis.

What about the FEMALE aging athlete?

What About the Window?

For years, athletes have been told to consume protein as soon as possible after training to take advantage of the “anabolic window,” which is thought to be the optimal time to enhance muscle gains and recovery through nutrition. Recently, some have been asserting that the anabolic window post-exercise has been disproven. But the window isn’t closed on that conversation…or the concept of the anabolic window.

The assertion that the anabolic window isn’t relevant arose from a meta-analyses on resistance trained individuals (which has several methodological issues, as do most meta-analyses- read more here) and other studies reporting that total protein intake across the day should count first, then the timing is an additional means of maximizing adaptations. Let’s dig a little deeper.

There are two primary goals of post-exercise nutrition, one being glycogen recovery, and the other, which is sometimes overlooked, is the reduction of muscle protein breakdown. Muscle protein breakdown is only slightly elevated post-exercise, but rapidly goes up soon after;  with some studies indicating ~50% increase still apparent three hours post-exercise. Once protein has been consumed, anabolism is increased for about three hours (with a peak at about 45 to 90 minutes), negating that three-hour peak muscle protein breakdown (as soon as you eat, it stops the breakdown). After those three hours post-food, muscle protein synthesis drops even though blood amino acid levels remain elevated. Although resistance training increases sensitivity to MPS for up to 24 hours, the agreement is there are likely advantages in consuming protein in close proximity to finishing exercise. With endurance exercise, there is total body protein oxidation, thus consuming a leucine-rich fast release protein (e.g. whey isolate) as close to the end of exercise as possible enhances overall metabolic recovery. Note here however, there is still very limited research on women, and we need to consider important sex differences.

Women return to baseline much faster, and more importantly, have different protein needs depending on their hormonal status. Protein oxidation during exercise appears to be greater during the mid-luteal phase. Females also require more lysine during the luteal phase than the follicular phase with a lower ability to uptake and utilize amino acids for protein synthesis. Women who use oral contraceptives (OC) have a different blood amino acid profile than naturally cycling women (the major influencer on protein metabolism and muscle adaptations is the generation of the progestin contained in the OC). Peri and post-menopausal women are increasingly resistant to muscle protein anabolism due to a lack of response to exercise and amino acid uptake (due to the change in the ratio of estrogen:progesterone and sensitivity of receptor sites). So, the picture is more complex for female athletes.

After intensive searches of the literature, we found that pre-menopausal, eumenorrheic, and oral contraceptive using female athletes should aim to consume a source of high-quality protein as close to beginning and/or after completion of exercise as possible to reduce exercise-induced amino acid oxidative losses and initiate muscle protein remodeling and repair at a dose of 0.32–0.38 grams per kilogram of body weight. Eumenorrheic women should aim for the upper end of the range ingestion during the luteal phase due to the catabolic actions of progesterone and greater need for amino acids.  With peri and postmenopausal athletes, the dose is more specific, and we’re looking for high essential amino acid (EAA)-containing (~10 g) intact protein sources or supplements to overcome anabolic resistance.

Insights on Supplements

The final section of the position stand takes a hard look at supplements. There is not much research done on women across the most popular sports supplements. We know that caffeine, iron, creatine, and beta-alanine have good evidence for use in women, with iron and creatine coming out on top for being highly efficacious in women. You can read the synopsis for each one in the paper.

One to keep an eye on especially is creatine, which is the subject of a great deal of research attention right now. A study just came out from Dr Abbie Smith-Ryan’s lab as part of Amanda Gordon’s PhD project, looking at creatine supplementation in the high hormone/luteal phase of the menstrual cycle. They found that sprint performance and recovery are reduced in this phase, but creatine loading during the luteal phase can help off-set this decrement. Exciting stuff, well worth checking out!

Overall, the goal of this Position Stand was to collate the existing research that was conducted with sound methodologies and create guidelines specific for women. We know that as more science emerges, these will change and be updated. Right now, we implore all scientists to take a hard look at what studies they are doing and to think carefully about improving the science done in women (for women, and hopefully more by female scientists!).

https://www.drstacysims.com/blog

What is the most nutrient dense food to consume for muscle protein synthesis?

Grass-fed beef is often touted for its potential nutrient benefits compared to conventionally raised, grain-fed beef. Here are some potential nutrient benefits associated with grass-fed beef:

1. Lower Total Fat Content:
   • Grass-fed beef tends to have a lower total fat content compared to grain-fed beef. This can result in a leaner meat product, which may be desirable for individuals looking to reduce overall fat intake.
2. Higher Omega-3 Fatty Acids:
   • Grass-fed beef is generally higher in omega-3 fatty acids, particularly alpha-linolenic acid (ALA), when compared to grain-fed beef. Omega-3 fatty acids are considered essential for heart health and have anti-inflammatory properties.
3. Higher Conjugated Linoleic Acid (CLA):
   • Grass-fed beef contains higher levels of conjugated linoleic acid (CLA), a type of fatty acid that has been associated with potential health benefits, including anti-cancer properties and improved body composition.
4. Increased Antioxidants:
   • Grass-fed beef may contain higher levels of certain antioxidants, including vitamins such as vitamin E and beta-carotene, which are associated with various health benefits.
5. Vitamins and Minerals:
   • Grass-fed beef is a good source of essential nutrients such as B-vitamins (e.g., B12, niacin, riboflavin), iron, zinc, and selenium. These nutrients are important for various physiological functions, including energy metabolism, immune function, and the formation of red blood cells.
6. No Antibiotics and Hormones:
   • Grass-fed beef is often produced without the use of antibiotics and hormones commonly used in conventional cattle farming. Some people choose grass-fed beef for environmental and ethical reasons, as well as to avoid potential residues of antibiotics and hormones in the meat.
7. Improved Fatty Acid Profile:
   • The diet of grass-fed cattle contributes to a more favorable fatty acid profile in the meat. While grain-fed beef may have a higher ratio of omega-6 to omega-3 fatty acids, grass-fed beef tends to have a more balanced ratio, which is considered beneficial for heart health.

It’s important to note that the nutrient composition of grass-fed beef can vary based on factors such as the animal’s diet, breed, and farming practices. Additionally, while grass-fed beef offers potential nutrient benefits, it may also be more expensive than conventionally raised beef. As with any food choice, it’s advisable to consider individual dietary needs, preferences, and budget when making decisions about the types of meat to include in your diet.