Ok, just started researching this..
don't know where I fall yet, but, I'll post it (with references) to let you guys start checking it out, too....
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...
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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.
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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.
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