Post-exercise refuelling: all at once, or spread out?


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We’ve all heard about the post-exercise “window” for refuelling to maximize recovery and adaption: you need to take in carbs and protein with 0.5-2 hours. But does the timing really matter for building muscle? A new study from Stuart Phillips’ group at McMaster University compared two tactics for post-workout protein intake. Once group took 25 grams of whey protein immediately after a set of leg-extension exercises; the other group received the same 25 grams of whey protein in 10 2.5-gram doses every 20 minutes for 200 minutes. They measured “muscle protein synthesis” — basically a very accurate way of assessing how well you’re stimulating muscle growth after a single bout rather than having to run the experiment for several months to actually see muscle growth — and found that it was much higher in the group that took their protein all at once. After six hours, protein synthesis was elevated by 193% in the single-shot group and just 121% in the prolonged group.

The question this study was seeking to answer actually relates to the difference between whey protein (which is absorbed quickly) and casein (which is absorbed more slowly: the 2.5 grams of whey every 20 minutes was chosen to mimic the absorption pattern of casein). The problem is that if you compare two different proteins in a study, then you’re changing a bunch of different factors at once — the absorption timing, but also factors like the amount of leucine, a branched-chain amino acid thought to be key for muscle growth. Since both groups received 25 grams of whey (and thus identical amounts of leucine), this shows that absorption rate is key.

Practical takeaway: this was a muscle protein synthesis study, not a training study, so you have take the results cautiously. But it does suggest that if you’re trying to build muscle, taking in a big dose (i.e. 25 grams) of protein as soon as possible is preferable to snacking over the course of a few hours. It also confirms previous findings suggesting that whey (found in dairy products) has some advantages over other protein sources.

10 Replies to “Post-exercise refuelling: all at once, or spread out?”

  1. Um, the proteins in milk are 80% casein by mass. Not an efficient source of whey proteins, especially considering how many people are either lactose intolerant or have difficulty digesting caseins.

  2. True, but dairy is still the best whey source we’ve got — other than human milk and whey protein powder, neither of which I’m eager to endorse! (If you’re really, really focused on bodybuilding, then whey protein powder is probably a good option. But for most people, I’d encourage them to rely on whole foods.)

  3. Whats your thoughts on raw egg whites (pasteurized) as a post-workout recovery food? A 250g carton is about 4 servings, so 120 cal, 28g protein. Sometimes coupled with 500ml of chocolate milk as well.

  4. @alex
    How about grass fed beef, bison, goats, & sheep, wild caught fish, other wild caught animals such as deer or elk, and chickens and turkeys that have run free and eaten bugs (NOT grains or soy). Let’s not forget all the pro-inflamatory issues with milk such as IGF-1, betacellulin, and a host of other hormones.

    Perhaps most problematic for most people, milk, being both a liquid food and containing huge doses of sugar, whey, and casein, is extremely insulinogenic. That’s not too problematic for post workout nutrition, thanks to non-insulin-mediated glucose transport and increased insulin sensitivity within 30 min of exercise. For general consumption, however, that insulin spike inhibits the metabolization of adipose tissue for energy, making the person feel like they need to eat more food. This leads to increased fat stores (so probably not a food you’d recommend to the folks in the study you published today) and, if regularly exposed to high insulin levels, Type II diabetes (insulin receptor cites down regulate their activity in response to chronically high insulin).

    Milk is a source of whey, but prefering it to animal flesh is a bit like ordering french fries instead of an apple because you want the starch in the potatoes instead of the fructose. Just sayin.

  5. @Jonas: I don’t have any experience with raw egg whites as a recovery food, but it sounds reasonable to me if that’s what you like! Basically, the key is finding something that’s (a) convenient and (b) palatable. No “perfect” recovery food is perfect if you don’t have it available when you need it, or don’t like it enough to take it in sufficient quantities.

    @Scott: I’m all in favour of bug-fed goats and other forms of real food. As for dairy products, if you believe they’re messing you up due to betacellulin, insulin spikes and whatever else, by all means avoid them. I haven’t seen any evidence that makes me think they’re a problem in reasonable quantities, but nutrition is complicated.

  6. @Scott

    This is complete nonsense.

    Many of the protein-rich foods you mention, just like milk, will raise insulin levels.

    An insulin spike will not make someone feel hungry and lead to increased fat stores, as insulin actually suppresses food intake.

  7. @Christian Finn

    Yes, actually Insulin does lead to feeling hungry and increased fat. That’s elementary biology. Insulin is THE fat storage hormone.

    A spike of insulin reduces blood sugar to levels too low, leading to cravings and hunger in an attempt to increase blood sugar levels again.

    Dairy, specifically Milk, contains a chemical called Insulin Like Growth Factor, which is actually molecularly identical between humans and bovines.

    This hormone ITSELF is HIGHLY insulogenic, never-mind the macro-nutrients in the foods.

    Practical evidence can be observed in thousands of cases where a major increase in dairy products has led to an increase in both fat and muscle mass in bodybuilders attempting to gain weight when nothing else could get them there.

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