Please Scroll Down to See Forums Below 
PursuitOfShredded
New member
I posted this on SC's thread, but, didn't think everyone would check it out there. I'm still working with my own diet/research and thought this may provide basis for debate for those interested. Lots of interesting info here, down to the type of protein our body likes.....
Lonnie M. Lowery, Ph.D. and Elzi Volk, M.S.
Tick, tick, tick...
Does it matter when you eat? Can you take advantage of particularly anabolic times throughout the day or avoid those periods when you're more likely to lay down body fat? You may be surprised to hear that the answer is YES!
What you eat and when you consume it matters a lot. By focusing upon different macronutrients (proteins, carbs, fats) as the day progresses, you just might be able to have fuller-looking muscles and a smaller gut (or butt). Think we're full of it? We’ll review 10 facts in this article and its successor, starting with these five...
--------------------------------------------------------------------------------
FACT 1:
A person has about two-three hours to take advantage of the "post workout nutrient window"
FACT 2:
Eating protein as well as carbohydrate shortly after exercise increases (muscle) protein synthesis and slows its degradation.
FACT 3:
Glucose tolerance worsens as the day progresses
FACT 4:
The body becomes catabolic during sleep, in part due to the extended fasting.
FACT 5:
Proteins with faster digestion are more anabolic.
--------------------------------------------------------------------------------
Let's see how we can take advantage of these important findings, shall we?
Fact 1: Post-workout nutrient window.
First, let's address the post-workout nutrient window. It used to be called the "post-workout carbohydrate window", but recent research has altered that view a bit. Basically, for a period of 1-3 hours after exercise, muscles are "greedy" for carbohydrates for reasons involving intracellular enzymes and glucose transporters. Consuming 0.7 to 1.6 g/ kg of total body weight (0.3-0.73 g/ lb TBW), or roughly 50-100 grams,6, 8,15 of rapidly digested and absorbed (high glycemic index) carbs during this window of opportunity is critical if you want to keep your muscles optimized for recovery and full looking. Keeping glycogen levels (formed from dietary carbs) high also appears to prevent (muscle) tissue breakdown, or “catabolism”.13
Training intensely, especially if you use negatives (eccentric contractions), makes it even more important to take advantage of the post-workout nutrient window. Why? Because the resulting muscle damage may hurt your muscles' ability to "soak up" the carbs after several hours pass and soreness sets in. (More on this in Part 2.) You want to refill muscle glycogen before this occurs which means taking in carbs as soon as possible after training.6
It’s generally a good idea to get plenty of carbs in right after training - even if you're avoiding them the rest of the day!15 In fact, additional small feedings of carbs after training may enhance repletion of glycogen in muscle tissue.3
Fact 2: Protein is important, too.
Although carbs were always thought to be 'top dog' for recovery, recent research shows that protein is just as important. New data from the renown Mark Tarnopolsky’s group at McMaster University, Ontario, Canada, reveals that increasing amino acid availability along with the circulating glucose can improve protein accretion (“non-oxidative leucine disposal”) following training.17 This was supported by data from Lonnie's "other lab" at Kent, the Applied Physiology Laboratory. It was here that colleague Phil Appicelli (see CreaRibose Research update) found similar results. And still more data agrees.2,16 All these data confirm the benefits of combining protein with one’s carbs.
In fact, protein alone is important for recovery. The ingestion of either 40 g mixed amino acids (17 different ones) or essential amino acids (10 different ones) about three hours post-exercise have been shown to change the net protein degradation experienced by weight trainers to net protein synthesis.18
Based on available data, you should eat perhaps 25-50 g of protein with your post-workout carbs. Since protein synthesis continues and peaks at about 24-36 hours after training,14 it's important to keep a steady supply of amino acids coming into your system by having small amounts of protein with each meal. Also, some of the recent research indicates that ingesting some protein before training may enhance protein synthesis afterward.19 Overall, it’s becoming pretty clear that eating protein with your carbs before, during, and after exercise is the ticket to increased muscle mass.
Fact 3: Glucose tolerance is better earlier in the day.
Your body's ability to handle dietary carbohydrate, in terms of keeping blood glucose within (low-to-mid) normal levels, fluctuates throughout the day. Of course, whatever the type of carbohydrate you eat, increased blood glucose is the result. Humans don’t have blood starch, fructose, or sucrose per se. These carbohydrates are digested (hydrolyzed) and absorbed as glucose. The balance of glucose supply and glucose utilization tightly controls normal levels of blood glucose, and insulin plays a key role in this process. [See graph.] Insulin inhibits glucose production/ release by the liver (where it is stored and manufactured) and stimulates glucose uptake by insulin sensitive tissues, such as muscle and adipose (body fat) tissues. However, just as in many of our hormone patterns, 24-hour variations occur in the overall glucose control system.
Many studies have shown that the blood glucose response to oral glucose and mixed meals (proteins, various carbs and fats) varies according to the time of day. Glucose levels are higher in the late afternoon and into the first half of the night. Some studies have suggested that these effects may be greater as we age, and are more prevalent in women than men. Researchers have gone so far as to described evening glucose tolerance in normal individuals as equivalent to mild diabetes!9 Wow!
Several mechanisms may explain the diurnal (time of day) variation in glucose tolerance. Insulin sensitivity is generally higher (better) in the morning and lower in the evening.12 Tissues like muscle appear to decrease their ability to take-up glucose later in the day.11 These morning-to-evening differences in glucose tolerance may possibly be due to changes in hormones and variations in the nervous system.20
As a consequence, tolerance to carbohydrate-rich meals declines as the day progresses. Eating low fat carb foods earlier in the day7 and reducing the carb content in meals as the day progresses may help to keep blood glucose better modulated. Over time, reduced body fat and fewer health problems (e.g. Syndrome X) may be the outcome. More research is necessary and of course kcal intake throughout the day is a consideration, but the literature is suggestive that evening carb reduction may be beneficial.
Fact 4: Nighttime shake can prevent muscle breakdown.
Each of us typically sleeps for a period of 6 to 9 hours, during which time our bodies enter the fasted state (because of the lack of food). Our bodies must therefore intervene to maintain stable glucose levels during this time. That glucose can come from various sources, depending on glycogen stores in several tissues: primarily glycogen stored in the liver. Hepatic (liver) cells have an enzyme called glucose-6-phosphatase that allows them to donate their glycogen/ glucose to keep blood glucose normal – and you alive – as you snooze for eight hours. As hepatic glycogen becomes depleted throughout the night, the body can start breaking down protein to make more glucose. Cortisol, which breaks down muscle tissue, and insulin, which isn’t around (much) to preserve it at this time, play important roles here.
By the way, if you train first thing in the morning without eating, reduced levels of liver glycogen may cause increased protein breakdown, so that your body can maintain blood glucose. Cortisol levels are high upon waking as it is.22 If you train first thing and your goal is maintained/ increased muscle mass, it's best to eat something (a small amount of carbs and protein) to avoid this. Eating before early morning exercise, conversely, could dampen fat loss. Thus, it depends on your goals.
If training before bedtime, a nighttime shake of mixed protein sources and some carbs should help prevent catabolism of muscle and enhance recovery while sleeping. The effects of exercise are likely to supersede the evening difficulties with glucose tolerance mentioned earlier. Admittedly, this is largely speculative at this point. Preventing sleep/ fasting-induced catabolism via dietary means is, in any case, an often-overlooked concept. Some athletes even go so far as to set an alarm and consume a late-night protein shake.
Fact 5: Easily digestible proteins are more anabolic.
Dietary protein digestion/ absorption rate can also affect protein deposition in the body, and thus muscle growth. Proteins that are rapidly digestible, such as whey, replenish the amino acid pool in the body quickly, supplying all the building blocks required for protein synthesis.5 This makes whey ideal for recovery and growth in your post-workout shake, to get amino acids to the just-worked muscles as soon as possible.
At this point, we’ve reviewed a number of issues emphasizing the critical timing of nutrient intake. As Dr. Peter Lemon notes in the recent text, Sports Supplements1: “Areas that need to be clarified involve not only which nutrients/ compounds affect the anabolic response induced by strength exercise, but also the best timing of intake relative to strength exercise…” Check back next month to learn more details on the five nutrient timing concepts discussed here as well as five more that round out our discussion.
PART II
Lonnie Lowery, Ph.D. and Elzi Volk, M.S.
Tick, tick, tick...
The clock is still ticking. Last time we cited some fascinating and applicable research on how to take advantage of particularly anabolic times throughout the day. We also pointed out periods and dietary situations in which you are at greater risk of muscle loss and fat gain. Ready for more? Let's review the final five facts on our nutrient timing “top ten”...
--------------------------------------------------------------------------------
FACT 6:
Proteins with slower digestion are anti-catabolic.
FACT 7:
Carbohydrates that raise blood glucose rapidly (high glycemic index) are best immediately post-exercise.
FACT 8:
Sore, damaged muscles resist glucose uptake.
FACT 9:
Carbohydrates may blunt the GH response to exercise, as fat does.
FACT 10:
Carbohydrates eaten before/ during training can reduce muscle catabolism but also blunt lipolysis (fat breakdown).
--------------------------------------------------------------------------------
Fact 6: “Slower” proteins inhibit protein breakdown.
Proteins that digest/ absorb more slowly, such as casein and most other dietary proteins, provide the body with amino acids gradually, over a longer period of time. One study showed that whole body protein breakdown was inhibited more (for several hours) after ingesting casein, but whole body protein synthesis was stimulated to a lesser degree than with ingestion of whey protein.(Dangin) This may make casein (and other dietary proteins) a better choice for other times during the day, to provide the body with a steady supply of amino acids.
Fact 7: High-glycemic carbs are best for post-exercise.
Considering the post-workout window of opportunity summarized in Fact 1, the best carbs to ingest right after training are those that are quickly digestible. High glycemic index (GI) carbs, such as glucose, glucose polymers or sucrose, are much more effective at stimulating glycogen resynthesis in the muscle tissue than fructose and other low-glycemic sources of carbs.(Ivy) The slower digestion and absorption of low-GI carbs delay the availability of glucose to the just worked muscle tissue.(Burke)
Fact 8: Muscle damage can blunt glucose uptake.
While the eccentric (lowering) portion of weight training exercises appears to be associated with muscle growth, too much could actually hinder growth. High intensity weight lifting that results in significant amounts of damage can reduce glucose uptake into the muscle and blunt glycogen accumulation. Data from the Human Performance Lab at Ball State University showed that glycogen levels were the same at 6 hours in the control and the exercised muscles of eccentrically trained men. (Widrick) However, at 24 and 72 hours, the eccentrically trained muscles contained significantly less glycogen than the control muscles. This fact is supported by data from the Human Nutrition Lab at Kent State. These data suggest that the athletes who get more sore and damaged from eccentric training (as assessed by higher creatine kinase spillage into the blood) are the ones who secrete more insulin to deal with an oral glucose tolerance test.(Sexton and Lowery) This is presumably a result of (relatively) glucose intolerant damaged muscles. Newer data from this lab also suggests that fasting insulin concentrations tend to be slightly higher in sore athletes - again revealing some difficulty handling dietary carbohydrate.
As mentioned, an emphasis on eccentric exercise often results in delayed-onset muscle soreness (DOMS), as well as causing damage to the muscle cell membrane. This damage alters glucose uptake into the muscle, which affects glycogen resynthesis. The time course of reduced muscle glycogen recompensation parallels that of the development of DOMS. In addition to cell membrane damage, the inflammatory response that accompanies soreness may also impair insulin binding. Furthermore, Doyle et al. of the Exercise Physiology Lab at Ohio State University showed a decrease in the enzyme, glycogen synthase, in eccentrically trained muscles compared to the concentrically trained.(Doyle) This enzyme is involved in synthesis of glycogen from glucose, and thus likely contributes to the reduction in glycogen replenishment.
Therefore, all of these effects of eccentric induced muscle damage may lead to impaired glucose uptake and glycogen resynthesis, which can harm both recovery and growth following training. If you train to the point of intense soreness in an effort to induce serious growth, allow a 5-7 day recovery period and perhaps reduce carb intake during periods of whole-body DOMS.
Fact 9: Carbs may blunt the GH response; fat does.
Although the scientific literature is equivocal and often misinterpreted, there may be some suppression of GH release when carbohydrate is consumed (Davies, Giustina, Jenkins) even prior to/ during exercise. (Bonen) Yet this isn't always found. (Cappon) Timing is critical, as a carb (and protein) meal could conceivably lead to hypoglycemia (low blood sugar) 60-90 minutes after ingestion and end up raising GH levels. This has, in fact, been demonstrated post-exercise. This scenario, where blood sugar is purposely driven downwards during an “insulin overshoot” would not be advisable immediately prior to training. It could cause fatigue. And lastly, a high fat pre-exercise meal has been shown to drop GH release by over 50% (Cappon), so those looking for GH release may want to avoid this.
Thus, if one is desirous of maximal somaotropin (GH) stimulation via exercise, especially to garner its lipolytic (fat burning) effects, it may be best to avoid carbohydrate for about two hours beforehand. Again, the literature is not 100% on this issue so some trainers may opt for the sense of fullness and energy that a light meal can bring, before heading to the gym.
Fact 10: Carbs will spare muscle but also spare fat.
Just as consuming nutrients, such as carbs or protein, can alter hormone concentrations at any time, they also influence the hormonal response to exercise. Exercise uses a mixture of fuel, such as stored glycogen, some blood glucose, and fat. When glycogen and blood glucose are lowered, the body relies more on fat for fuel and vice versa. It seems intuitive that the body would readily dip into it’s fat reserves when there is little else to “burn” metabolically. It also makes sense that the body would shy away from carbohydrate as a metabolic fuel when there is little to spare. Many exercisers put this knowledge to work, exercising fasted, upon rising in an attempt to enhance the total grams of fat lost.
But what if you’re already lean? What if your goal is to gain sheer weight with little regard for fat loss? This is a valid desire of many ectomorphic (thin) “hard gainers”. In this case, one’s strategy is nearly opposite to the one described above. Hard gainers care little that carb intake blunts lipolysis. The truth is, dietary carb (and protein) consumption prior to, during, and after exercise is generally good for muscle gain. Purposely timing carb intake around one’s training bout elevates blood glucose and insulin concentrations while reducing cortisol and interleukin-6, all of which help prevent muscle breakdown. (Deuster, Mitchel, Murray, Nieman)
Manipulating the ingestion of carbs in relation to exercise, therefore, is critical to reach one’s goals whether they are to lean out or bulk up. Perhaps the best approach is to vary the strategy throughout the year. Many athletes undertake a “mass building phase” in the Fall but switch to a “cutting phase” in Spring/ Summer.
So there you have it, a short but well-referenced treatise on nutrient timing. Now it’s time to put this new understanding to work and break out of that plateau in your physique development. Good luck.
References and Additional Reading
Antonio, J. and Stout, J. Sports Supplements. Lippincott, Williams and Wilkins, 2001.
Biolo G, Tipton KD, Klein S, Wolfe RR. An abundant supply of amino acids enchances the metabolic effect of exercise on muscle protein. Am J Physiol 1997; 273(36):E122.
Bonen, A., et al. Hormonal responses during intense exercise preceded by glucose ingestion.Can J Appl Sport Sci 1980 Jun;5(2):85-90.
Burke LM, Collier GR, Davis PG, et al. Muscle glycogen storage after prolonged exercise: effect of the frequency of carbohydrate feedings. Am J Clin Nutr 1996; 64:115.
Cappon, J., et al. Acute effects of high fat and high glucose meals on the growth hormone response to exercise. J Clin Endocrinol Metab 1993 Jun;76(6):1418-22.
Chandler RM, Byrne HK, Ivy JL, et al. Dietary supplements affect the anabolic hormones after weight training exercise. J Appl Physiol 1994; 76(2):839.
Dangin M, Boirie Y, Garcia-Rodenas C, et al. The digestion rate of protein is an independent regulating factor of postprandial protein retention. Am J Physiol Endocrinol Metab 2001;280(2):E340.
Davies, R., et al. Oral glucose inhibits growth hormone secretion induced by human pancreatic growth hormone releasing factor 1-44 in normal man. Clin Endocrinol 21(4) (1984 Oct): 477-81.
Doyle JA, Sherman WM, Strauss RL. Effects of eccentric and concentric exercise on muscle glycogen replenishment. J Appl Physiol 1993; 74(4A):1848-1855.
Deuster, P., et al. Hormonal responses to ingesting water or a carbohydrate beverage during a 2 h run. Med Sci Sports Exerc. Jan;24(1):72-9,1992.
Frape, D., et al. Effect of breakfast fat content on glucose tolerance and risk factors of atherosclerosis and thrombosis. Br J Nutr 1998 Oct;80(4):323-31.
Friedman, J. et al. Regulation of glycogen resynthesis following exercise. Dietary considerations. Sports Med 1991; 11(4):232-43.
Giustina, A., et al. Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human. Endocrine Reviews 19 (6): 717-797.
Grabner, W., et al. Diurnal variation of glucose tolerance and insulin secretion in man. Klin Wochenschr 1975 Aug 15;53(16):773-8.
Ivy JL. Muscle glycogen synthesis before and after exercise. Sports Med 1991; 11(1):6.
Jenkins, D., et al. Metabolic effects of reducing rate of glucose ingestion by single bolus versus continuous sipping. Diabetes 39(7) (1990 Jul): 775-81.
JVerrillo A, De Teresa A, Martino C, et al. Differential roles of splanchnic and peripheral tissues in determining diurnal fluctuation of glucose tolerance. Am J Physiol 1989; 257(4 pt 1):E459.
Lee A, Ader M, Bray GA, Bergman RN. Diurnal variation in glucose tolerance. Cyclic suppression of insulin action and insulin secretion in normal-weight, but not obese, subjects. Diabetes 1992; 41(6):742.
Lemon PW, Mullin. Effect of initial muscle glycogen levels on protein catabolism during exercise. JP. J Appl Physiol 1980;48(4):624-9.
MacDougall JD, Gibala MJ, Tarnopolsky MA, et al. The time course for elevated muscle protein synthesis following heavy resistance exercise. Can J Appl Physiol 1995; 20(45):480.
Mitchell, J., et al. Influence of carbohydrate ingestion on counterregulatory hormones during prolonged exercise. Int J Sports Med. Feb;11(1):33-6, 1990.
Murray, R., et al. Responses to varying rates of carbohydrate ingestion during exercise. Med Sci Sports Exerc. Jun;23(6):713-8,1991.
Nieman DC, Influence of mode and carbohydrate on the cytokine response to heavy exertion. Med Sci Sports Exerc May;30(5):671-678, 1998.
Pascoe DD, Costill DL, Fink WJ, et al. Glycogen resynthesis in skeletal muscle following resistive exercise. Med Sci Sports Exer 1993; 25(3):349.
Rassmussen, B., et al. An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise. J Appl Physiol 2000; 88: 386.
Roy, B. et al. Macronutrient intake and whole body protein metabolism following resistance exercise. Med Sci Sports Exerc 2000; 32(8):1412.
Sexton, T. and Lowery, L. (2001). Oh J Sci (Medicine and Biology), 101 (1): 13.
Tipton, K., Ferrando, A., Phillips, S., et al. Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol 1999; 276 (Endcrinol Metab):E628.
Tipton, K., et al. Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab 2001 Aug;281(2):E197-206
Van Cauter E, Polonsky KS, Scheen AJ. Roles of circadian rhythmicity and sleep in human glucose regulation. Endo Rev 1997; 18(5):716.
Widrick JJ, Costill DL, McConell GK, et al. Time course of glycogen accumulation after eccentric training. J Appl Physiol 1992; 72(5):1999.
Williams, R. Textbook of Clinical Endocrinology. 1974. WB Saunders Co.: Philadelphia.
Lonnie M. Lowery, Ph.D. and Elzi Volk, M.S.
Tick, tick, tick...
Does it matter when you eat? Can you take advantage of particularly anabolic times throughout the day or avoid those periods when you're more likely to lay down body fat? You may be surprised to hear that the answer is YES!
What you eat and when you consume it matters a lot. By focusing upon different macronutrients (proteins, carbs, fats) as the day progresses, you just might be able to have fuller-looking muscles and a smaller gut (or butt). Think we're full of it? We’ll review 10 facts in this article and its successor, starting with these five...
--------------------------------------------------------------------------------
FACT 1:
A person has about two-three hours to take advantage of the "post workout nutrient window"
FACT 2:
Eating protein as well as carbohydrate shortly after exercise increases (muscle) protein synthesis and slows its degradation.
FACT 3:
Glucose tolerance worsens as the day progresses
FACT 4:
The body becomes catabolic during sleep, in part due to the extended fasting.
FACT 5:
Proteins with faster digestion are more anabolic.
--------------------------------------------------------------------------------
Let's see how we can take advantage of these important findings, shall we?
Fact 1: Post-workout nutrient window.
First, let's address the post-workout nutrient window. It used to be called the "post-workout carbohydrate window", but recent research has altered that view a bit. Basically, for a period of 1-3 hours after exercise, muscles are "greedy" for carbohydrates for reasons involving intracellular enzymes and glucose transporters. Consuming 0.7 to 1.6 g/ kg of total body weight (0.3-0.73 g/ lb TBW), or roughly 50-100 grams,6, 8,15 of rapidly digested and absorbed (high glycemic index) carbs during this window of opportunity is critical if you want to keep your muscles optimized for recovery and full looking. Keeping glycogen levels (formed from dietary carbs) high also appears to prevent (muscle) tissue breakdown, or “catabolism”.13
Training intensely, especially if you use negatives (eccentric contractions), makes it even more important to take advantage of the post-workout nutrient window. Why? Because the resulting muscle damage may hurt your muscles' ability to "soak up" the carbs after several hours pass and soreness sets in. (More on this in Part 2.) You want to refill muscle glycogen before this occurs which means taking in carbs as soon as possible after training.6
It’s generally a good idea to get plenty of carbs in right after training - even if you're avoiding them the rest of the day!15 In fact, additional small feedings of carbs after training may enhance repletion of glycogen in muscle tissue.3
Fact 2: Protein is important, too.
Although carbs were always thought to be 'top dog' for recovery, recent research shows that protein is just as important. New data from the renown Mark Tarnopolsky’s group at McMaster University, Ontario, Canada, reveals that increasing amino acid availability along with the circulating glucose can improve protein accretion (“non-oxidative leucine disposal”) following training.17 This was supported by data from Lonnie's "other lab" at Kent, the Applied Physiology Laboratory. It was here that colleague Phil Appicelli (see CreaRibose Research update) found similar results. And still more data agrees.2,16 All these data confirm the benefits of combining protein with one’s carbs.
In fact, protein alone is important for recovery. The ingestion of either 40 g mixed amino acids (17 different ones) or essential amino acids (10 different ones) about three hours post-exercise have been shown to change the net protein degradation experienced by weight trainers to net protein synthesis.18
Based on available data, you should eat perhaps 25-50 g of protein with your post-workout carbs. Since protein synthesis continues and peaks at about 24-36 hours after training,14 it's important to keep a steady supply of amino acids coming into your system by having small amounts of protein with each meal. Also, some of the recent research indicates that ingesting some protein before training may enhance protein synthesis afterward.19 Overall, it’s becoming pretty clear that eating protein with your carbs before, during, and after exercise is the ticket to increased muscle mass.
Fact 3: Glucose tolerance is better earlier in the day.
Your body's ability to handle dietary carbohydrate, in terms of keeping blood glucose within (low-to-mid) normal levels, fluctuates throughout the day. Of course, whatever the type of carbohydrate you eat, increased blood glucose is the result. Humans don’t have blood starch, fructose, or sucrose per se. These carbohydrates are digested (hydrolyzed) and absorbed as glucose. The balance of glucose supply and glucose utilization tightly controls normal levels of blood glucose, and insulin plays a key role in this process. [See graph.] Insulin inhibits glucose production/ release by the liver (where it is stored and manufactured) and stimulates glucose uptake by insulin sensitive tissues, such as muscle and adipose (body fat) tissues. However, just as in many of our hormone patterns, 24-hour variations occur in the overall glucose control system.
Many studies have shown that the blood glucose response to oral glucose and mixed meals (proteins, various carbs and fats) varies according to the time of day. Glucose levels are higher in the late afternoon and into the first half of the night. Some studies have suggested that these effects may be greater as we age, and are more prevalent in women than men. Researchers have gone so far as to described evening glucose tolerance in normal individuals as equivalent to mild diabetes!9 Wow!
Several mechanisms may explain the diurnal (time of day) variation in glucose tolerance. Insulin sensitivity is generally higher (better) in the morning and lower in the evening.12 Tissues like muscle appear to decrease their ability to take-up glucose later in the day.11 These morning-to-evening differences in glucose tolerance may possibly be due to changes in hormones and variations in the nervous system.20
As a consequence, tolerance to carbohydrate-rich meals declines as the day progresses. Eating low fat carb foods earlier in the day7 and reducing the carb content in meals as the day progresses may help to keep blood glucose better modulated. Over time, reduced body fat and fewer health problems (e.g. Syndrome X) may be the outcome. More research is necessary and of course kcal intake throughout the day is a consideration, but the literature is suggestive that evening carb reduction may be beneficial.
Fact 4: Nighttime shake can prevent muscle breakdown.
Each of us typically sleeps for a period of 6 to 9 hours, during which time our bodies enter the fasted state (because of the lack of food). Our bodies must therefore intervene to maintain stable glucose levels during this time. That glucose can come from various sources, depending on glycogen stores in several tissues: primarily glycogen stored in the liver. Hepatic (liver) cells have an enzyme called glucose-6-phosphatase that allows them to donate their glycogen/ glucose to keep blood glucose normal – and you alive – as you snooze for eight hours. As hepatic glycogen becomes depleted throughout the night, the body can start breaking down protein to make more glucose. Cortisol, which breaks down muscle tissue, and insulin, which isn’t around (much) to preserve it at this time, play important roles here.
By the way, if you train first thing in the morning without eating, reduced levels of liver glycogen may cause increased protein breakdown, so that your body can maintain blood glucose. Cortisol levels are high upon waking as it is.22 If you train first thing and your goal is maintained/ increased muscle mass, it's best to eat something (a small amount of carbs and protein) to avoid this. Eating before early morning exercise, conversely, could dampen fat loss. Thus, it depends on your goals.
If training before bedtime, a nighttime shake of mixed protein sources and some carbs should help prevent catabolism of muscle and enhance recovery while sleeping. The effects of exercise are likely to supersede the evening difficulties with glucose tolerance mentioned earlier. Admittedly, this is largely speculative at this point. Preventing sleep/ fasting-induced catabolism via dietary means is, in any case, an often-overlooked concept. Some athletes even go so far as to set an alarm and consume a late-night protein shake.
Fact 5: Easily digestible proteins are more anabolic.
Dietary protein digestion/ absorption rate can also affect protein deposition in the body, and thus muscle growth. Proteins that are rapidly digestible, such as whey, replenish the amino acid pool in the body quickly, supplying all the building blocks required for protein synthesis.5 This makes whey ideal for recovery and growth in your post-workout shake, to get amino acids to the just-worked muscles as soon as possible.
At this point, we’ve reviewed a number of issues emphasizing the critical timing of nutrient intake. As Dr. Peter Lemon notes in the recent text, Sports Supplements1: “Areas that need to be clarified involve not only which nutrients/ compounds affect the anabolic response induced by strength exercise, but also the best timing of intake relative to strength exercise…” Check back next month to learn more details on the five nutrient timing concepts discussed here as well as five more that round out our discussion.
PART II
Lonnie Lowery, Ph.D. and Elzi Volk, M.S.
Tick, tick, tick...
The clock is still ticking. Last time we cited some fascinating and applicable research on how to take advantage of particularly anabolic times throughout the day. We also pointed out periods and dietary situations in which you are at greater risk of muscle loss and fat gain. Ready for more? Let's review the final five facts on our nutrient timing “top ten”...
--------------------------------------------------------------------------------
FACT 6:
Proteins with slower digestion are anti-catabolic.
FACT 7:
Carbohydrates that raise blood glucose rapidly (high glycemic index) are best immediately post-exercise.
FACT 8:
Sore, damaged muscles resist glucose uptake.
FACT 9:
Carbohydrates may blunt the GH response to exercise, as fat does.
FACT 10:
Carbohydrates eaten before/ during training can reduce muscle catabolism but also blunt lipolysis (fat breakdown).
--------------------------------------------------------------------------------
Fact 6: “Slower” proteins inhibit protein breakdown.
Proteins that digest/ absorb more slowly, such as casein and most other dietary proteins, provide the body with amino acids gradually, over a longer period of time. One study showed that whole body protein breakdown was inhibited more (for several hours) after ingesting casein, but whole body protein synthesis was stimulated to a lesser degree than with ingestion of whey protein.(Dangin) This may make casein (and other dietary proteins) a better choice for other times during the day, to provide the body with a steady supply of amino acids.
Fact 7: High-glycemic carbs are best for post-exercise.
Considering the post-workout window of opportunity summarized in Fact 1, the best carbs to ingest right after training are those that are quickly digestible. High glycemic index (GI) carbs, such as glucose, glucose polymers or sucrose, are much more effective at stimulating glycogen resynthesis in the muscle tissue than fructose and other low-glycemic sources of carbs.(Ivy) The slower digestion and absorption of low-GI carbs delay the availability of glucose to the just worked muscle tissue.(Burke)
Fact 8: Muscle damage can blunt glucose uptake.
While the eccentric (lowering) portion of weight training exercises appears to be associated with muscle growth, too much could actually hinder growth. High intensity weight lifting that results in significant amounts of damage can reduce glucose uptake into the muscle and blunt glycogen accumulation. Data from the Human Performance Lab at Ball State University showed that glycogen levels were the same at 6 hours in the control and the exercised muscles of eccentrically trained men. (Widrick) However, at 24 and 72 hours, the eccentrically trained muscles contained significantly less glycogen than the control muscles. This fact is supported by data from the Human Nutrition Lab at Kent State. These data suggest that the athletes who get more sore and damaged from eccentric training (as assessed by higher creatine kinase spillage into the blood) are the ones who secrete more insulin to deal with an oral glucose tolerance test.(Sexton and Lowery) This is presumably a result of (relatively) glucose intolerant damaged muscles. Newer data from this lab also suggests that fasting insulin concentrations tend to be slightly higher in sore athletes - again revealing some difficulty handling dietary carbohydrate.
As mentioned, an emphasis on eccentric exercise often results in delayed-onset muscle soreness (DOMS), as well as causing damage to the muscle cell membrane. This damage alters glucose uptake into the muscle, which affects glycogen resynthesis. The time course of reduced muscle glycogen recompensation parallels that of the development of DOMS. In addition to cell membrane damage, the inflammatory response that accompanies soreness may also impair insulin binding. Furthermore, Doyle et al. of the Exercise Physiology Lab at Ohio State University showed a decrease in the enzyme, glycogen synthase, in eccentrically trained muscles compared to the concentrically trained.(Doyle) This enzyme is involved in synthesis of glycogen from glucose, and thus likely contributes to the reduction in glycogen replenishment.
Therefore, all of these effects of eccentric induced muscle damage may lead to impaired glucose uptake and glycogen resynthesis, which can harm both recovery and growth following training. If you train to the point of intense soreness in an effort to induce serious growth, allow a 5-7 day recovery period and perhaps reduce carb intake during periods of whole-body DOMS.
Fact 9: Carbs may blunt the GH response; fat does.
Although the scientific literature is equivocal and often misinterpreted, there may be some suppression of GH release when carbohydrate is consumed (Davies, Giustina, Jenkins) even prior to/ during exercise. (Bonen) Yet this isn't always found. (Cappon) Timing is critical, as a carb (and protein) meal could conceivably lead to hypoglycemia (low blood sugar) 60-90 minutes after ingestion and end up raising GH levels. This has, in fact, been demonstrated post-exercise. This scenario, where blood sugar is purposely driven downwards during an “insulin overshoot” would not be advisable immediately prior to training. It could cause fatigue. And lastly, a high fat pre-exercise meal has been shown to drop GH release by over 50% (Cappon), so those looking for GH release may want to avoid this.
Thus, if one is desirous of maximal somaotropin (GH) stimulation via exercise, especially to garner its lipolytic (fat burning) effects, it may be best to avoid carbohydrate for about two hours beforehand. Again, the literature is not 100% on this issue so some trainers may opt for the sense of fullness and energy that a light meal can bring, before heading to the gym.
Fact 10: Carbs will spare muscle but also spare fat.
Just as consuming nutrients, such as carbs or protein, can alter hormone concentrations at any time, they also influence the hormonal response to exercise. Exercise uses a mixture of fuel, such as stored glycogen, some blood glucose, and fat. When glycogen and blood glucose are lowered, the body relies more on fat for fuel and vice versa. It seems intuitive that the body would readily dip into it’s fat reserves when there is little else to “burn” metabolically. It also makes sense that the body would shy away from carbohydrate as a metabolic fuel when there is little to spare. Many exercisers put this knowledge to work, exercising fasted, upon rising in an attempt to enhance the total grams of fat lost.
But what if you’re already lean? What if your goal is to gain sheer weight with little regard for fat loss? This is a valid desire of many ectomorphic (thin) “hard gainers”. In this case, one’s strategy is nearly opposite to the one described above. Hard gainers care little that carb intake blunts lipolysis. The truth is, dietary carb (and protein) consumption prior to, during, and after exercise is generally good for muscle gain. Purposely timing carb intake around one’s training bout elevates blood glucose and insulin concentrations while reducing cortisol and interleukin-6, all of which help prevent muscle breakdown. (Deuster, Mitchel, Murray, Nieman)
Manipulating the ingestion of carbs in relation to exercise, therefore, is critical to reach one’s goals whether they are to lean out or bulk up. Perhaps the best approach is to vary the strategy throughout the year. Many athletes undertake a “mass building phase” in the Fall but switch to a “cutting phase” in Spring/ Summer.
So there you have it, a short but well-referenced treatise on nutrient timing. Now it’s time to put this new understanding to work and break out of that plateau in your physique development. Good luck.
References and Additional Reading
Antonio, J. and Stout, J. Sports Supplements. Lippincott, Williams and Wilkins, 2001.
Biolo G, Tipton KD, Klein S, Wolfe RR. An abundant supply of amino acids enchances the metabolic effect of exercise on muscle protein. Am J Physiol 1997; 273(36):E122.
Bonen, A., et al. Hormonal responses during intense exercise preceded by glucose ingestion.Can J Appl Sport Sci 1980 Jun;5(2):85-90.
Burke LM, Collier GR, Davis PG, et al. Muscle glycogen storage after prolonged exercise: effect of the frequency of carbohydrate feedings. Am J Clin Nutr 1996; 64:115.
Cappon, J., et al. Acute effects of high fat and high glucose meals on the growth hormone response to exercise. J Clin Endocrinol Metab 1993 Jun;76(6):1418-22.
Chandler RM, Byrne HK, Ivy JL, et al. Dietary supplements affect the anabolic hormones after weight training exercise. J Appl Physiol 1994; 76(2):839.
Dangin M, Boirie Y, Garcia-Rodenas C, et al. The digestion rate of protein is an independent regulating factor of postprandial protein retention. Am J Physiol Endocrinol Metab 2001;280(2):E340.
Davies, R., et al. Oral glucose inhibits growth hormone secretion induced by human pancreatic growth hormone releasing factor 1-44 in normal man. Clin Endocrinol 21(4) (1984 Oct): 477-81.
Doyle JA, Sherman WM, Strauss RL. Effects of eccentric and concentric exercise on muscle glycogen replenishment. J Appl Physiol 1993; 74(4A):1848-1855.
Deuster, P., et al. Hormonal responses to ingesting water or a carbohydrate beverage during a 2 h run. Med Sci Sports Exerc. Jan;24(1):72-9,1992.
Frape, D., et al. Effect of breakfast fat content on glucose tolerance and risk factors of atherosclerosis and thrombosis. Br J Nutr 1998 Oct;80(4):323-31.
Friedman, J. et al. Regulation of glycogen resynthesis following exercise. Dietary considerations. Sports Med 1991; 11(4):232-43.
Giustina, A., et al. Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human. Endocrine Reviews 19 (6): 717-797.
Grabner, W., et al. Diurnal variation of glucose tolerance and insulin secretion in man. Klin Wochenschr 1975 Aug 15;53(16):773-8.
Ivy JL. Muscle glycogen synthesis before and after exercise. Sports Med 1991; 11(1):6.
Jenkins, D., et al. Metabolic effects of reducing rate of glucose ingestion by single bolus versus continuous sipping. Diabetes 39(7) (1990 Jul): 775-81.
JVerrillo A, De Teresa A, Martino C, et al. Differential roles of splanchnic and peripheral tissues in determining diurnal fluctuation of glucose tolerance. Am J Physiol 1989; 257(4 pt 1):E459.
Lee A, Ader M, Bray GA, Bergman RN. Diurnal variation in glucose tolerance. Cyclic suppression of insulin action and insulin secretion in normal-weight, but not obese, subjects. Diabetes 1992; 41(6):742.
Lemon PW, Mullin. Effect of initial muscle glycogen levels on protein catabolism during exercise. JP. J Appl Physiol 1980;48(4):624-9.
MacDougall JD, Gibala MJ, Tarnopolsky MA, et al. The time course for elevated muscle protein synthesis following heavy resistance exercise. Can J Appl Physiol 1995; 20(45):480.
Mitchell, J., et al. Influence of carbohydrate ingestion on counterregulatory hormones during prolonged exercise. Int J Sports Med. Feb;11(1):33-6, 1990.
Murray, R., et al. Responses to varying rates of carbohydrate ingestion during exercise. Med Sci Sports Exerc. Jun;23(6):713-8,1991.
Nieman DC, Influence of mode and carbohydrate on the cytokine response to heavy exertion. Med Sci Sports Exerc May;30(5):671-678, 1998.
Pascoe DD, Costill DL, Fink WJ, et al. Glycogen resynthesis in skeletal muscle following resistive exercise. Med Sci Sports Exer 1993; 25(3):349.
Rassmussen, B., et al. An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise. J Appl Physiol 2000; 88: 386.
Roy, B. et al. Macronutrient intake and whole body protein metabolism following resistance exercise. Med Sci Sports Exerc 2000; 32(8):1412.
Sexton, T. and Lowery, L. (2001). Oh J Sci (Medicine and Biology), 101 (1): 13.
Tipton, K., Ferrando, A., Phillips, S., et al. Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol 1999; 276 (Endcrinol Metab):E628.
Tipton, K., et al. Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab 2001 Aug;281(2):E197-206
Van Cauter E, Polonsky KS, Scheen AJ. Roles of circadian rhythmicity and sleep in human glucose regulation. Endo Rev 1997; 18(5):716.
Widrick JJ, Costill DL, McConell GK, et al. Time course of glycogen accumulation after eccentric training. J Appl Physiol 1992; 72(5):1999.
Williams, R. Textbook of Clinical Endocrinology. 1974. WB Saunders Co.: Philadelphia.
