I’ve been doing a bit of forum posting and thinking about post-workout nutrition…I read an article over at Tri-Fuel. Here’s what the article said:
So initially, here was my response:
After that, I received some questions about how and what *should* be eaten post-workout, after regular workouts, after distance workouts, etc…so I wanted to share with you my response to that.
First of all, let me begin by saying that David Warden will graciously be allowing me to guest host an episode of the Tri Talk podcast to discuss the post-workout feeding issue in more detail. So stay posted for that, along with some more talk about this on my podcast at http://www.bengreenfieldfitness.com.
An example of one of the first studies to investigate whether mixing carbohydrate and protein is better than having carbohydrate alone can be summarized as follows:
Tarnopolsky, M. A., M. Bosman, J. R. MacDonald, D. Vandeputte, J. Martin, and B. D. Roy. Postexercise protein-carbohydrate and carbohydrate supplements increase muscle glycogen in men and women. J. Appl. Physiol. 83(6): 1877-1883, 1997.We have previously demonstrated that women did not increase intramuscular glycogen in response to an increased percent of dietary carbohydrate (CHO) (from 60 to 75% of energy intake) (M. A. Tarnopolsky, S. A. Atkinson, S. M. Phillips, and J. D. MacDougall. J. Appl. Physiol. 78: 1360-1368, 1995). CHO and CHO-protein (Pro) supplementation postexercise can potentiate glycogen resynthesis compared with placebo (K. M. Zawadzki, B. B. Yaspelkis, and J. L. Ivy. J. Appl. Physiol. 72: 1854-1859, 1992). We studied the effect of isoenergetic CHO and CHO-Pro-Fat supplements on muscle glycogen resynthesis in the first 4 h after endurance exercise (90 min at 65% peak O2 consumption) in trained endurance athletes (men, n = 8; women, tested in midfollicular phase, n = 8). Each subject completed three sequential trials separated by 3 wk; a supplement was provided immediately and 1-h postexercise: 1) CHO (0.75 g/kg) + Pro (0.1 g/kg) + Fat (0.02 g/kg), 2) CHO (1 g/kg), and 3) placebo (Pl; artificial sweetener). Subjects were given prepackaged, isoenergetic, isonitrogenous diets, individualized to their habitual diet, for the day before and during the exercise trial. During exercise, women oxidized more lipid than did men (P < 0.05). Both of the supplement trials resulted in greater postexercise glucose and insulin compared with Pl (P < 0.01), with no gender differences. Similarly, both of these trials resulted in increased glycogen resynthesis (37.2 vs. 24.6 mmol · kg dry muscle1 · h1, CHO vs. CHO-Pro-Fat, respectively) compared with Pl (7.5 mmol · kg dry muscle1 · h1; P < 0.001) with no gender differences. We conclude that postexercise CHO and CHO-Pro-Fat nutritional supplements can increase glycogen resynthesis to a greater extent than Pl for both men and women.
This, and the studies that have been done since then (like this one that you geeks can read in full for free: http://www.ajcn.org/cgi/content/full/72/1/106), suggest primarily the reason that the carbohydrate will enhance protein uptake is due to the insulin response with the sugar intake. Insulin is an anabolic hormone that causes energy uptake and storage, and is essential to stimulate the uptake of amino acids. There is also a vice-versa effect – protein can act as a “chaperone” to assist with the carb absorption.
The rub is this: MOST folks aren’t exercising hard enough or long enough to justify re-fueling when they already have enough amino acids and sugar on board from pre and during workout feeding.
You can figure out whether you need a post-workout meal pretty easily. Let’s start by estimating about how much storage carbohydrate energy you have on board to start with. Your maximal carbohydrate storage is approximately 15 grams per kilogram of body weight [15 grams per 2.2 pounds]. So a 175-pound athlete could store up to 1200 grams of carbohydrate [4,800 calories]; enough energy to fuel high intensity exercise for quite some time.
So let’s say this 175lb person eats a bowl of oatmeal with some peanut butter (~600 calories), then goes on a 2 hour bike ride at 600 calories per hour. They arrive home at a 600 calorie deficit. Meaning they have 4200 calories of storage carbohydrate STILL ON BOARD.
Now, they hear about this post-workout need, and rush off to eat so they can have a “good workout the next day”, but is that really necessary. Let’s look at how long it would take to replace glycogen, or storage carbohydrate.
Unfortunately, in the scientific literature, glycogen restoration rates are measured in funky units like glycosol per gram or mumol.g wet wt-1.h-1, or mmol/kg – tough to translate into actual real world numbers for us normal folks. But I’m going to try.
5mmol of glucose is 1 gram. Assuming the glycogen is cleanly broken down into glucose, then 5.5mmol of glycogen is 4 calories, since there’s 4 calories in a gram. Post-exercise glycogen re-synthesis rates fall right around the 10mmol/kg/hr range, which is 4.5mmol/lb/hr, so for a 175lb individual, you looking at 785mmol/hr, which is 157g/hr, which is 630 calories per hour.
In other words, a conservative rate of glycogen re-synthesis for you is 630 calories per hour, for up to 2 hours after exercise. So why the heck would you be trying to replace glycogen stores by shoving 800 calories of carbohydrate down the hatch just 20-30 minutes after exercise?
Your goal after a typical workout should instead be to A) re-hydrate and B) elevate amino acids to limit muscle catabolism by consuming 0.25g protein per lb of body weight, with a small amount of sugar to elevate insulin levels. So, for example, the 175lb person could eat about 45g of protein power mixed into 100-200 calories carbohydrate (i.e. a couple bananas with a couple scoops whey protein).
What about for a more serious, glycogen depleting workout, like a 100 mile bike ride, followed by a run later in the day? That’s when you can and should focus on maximizing carbohydrate restoration. Here’s a good rule to follow based on research:
Simply multiply your weight in pounds by three. Divide the result by 16 to determine the number of grams of carbohydrate to eat every 15 minutes. Example: You weighs 175 pounds. 175 X 3 = 525. 525/16 = 33 grams or 132 calories of carbohydrate, which should be ingested every 15 minutes. And you do that for 4 hours.
Notice I said “based on research”. If you’re not a lab rat and can’t mow through a bottle of Gatorade every 15 minutes for 4 hours, then just figure out way to creatively consume 2000 calories of about 25% protein, 75% carbohydrate in the 4 hours following your workout, and try and finish that eating about 2 hours before you start your next workout. I’ll wager a bet that you can creatively figure out how to eat 2000 calories in 4 hours. And remember, that’s for “Ironman style” two-a-day workouts, so it’s mostly the pro triathlete that’s going to be worrying about this.
OK, I’m done ranting! Here’s where I do end with a shameless plug – you should read my book “Holistic Fueling For Ironman Triathletes” if you haven’t yet – so you can learn how to eat lots of calories without destroying your body. It’s free inside your member’s area here at the Rock Star Triathlete Academy.
Also, leave a comment if you have questions or thoughts.