Thursday, May 21, 2015

Sports Nutrition 4: What I Learned About (Re-)Fueling

(Say it with me now: I am not a nutritionist or dietician or really any kind of expert at this stuff, and all of this is based on what ONE sports nutritionist explained to me about MY particular situation and needs. I'm happy to entertain questions if people have them--just know that I may not know the answer, and if I try to guess based on what I *think* I understand, I may get it wrong. But, I hope this helps provide some insight about sports nutrition to people who are interested!)

If you have been reading this blog for any amount of time, you probably know that I am a complete and total data/numbers geek. I taught high school math for 8 years & now do research/analysis work in math & science education in my day job. Quantitative modeling = totally my jam.

So when Dr. C. & I came to the point of discussing when/how/how much to refuel after exercise, we kind of had this moment where he was basically like, "Do you actually want to know how the sausage is made, or do you just want me to, like, tell you what to do?," I was like, "ALL THE TECHNICAL DETAILS, PLZTHNX," and we went from there.

(I guess what I'm saying is, if you are allergic to numbers & calculations, hang in there--It's really not that bad & I promise I will summarize at the end.)

I mentioned some of this in the breakfast post regarding refueling from my morning strength workouts. The thing is, people--even athletes--have all kind of messed up, completely inaccurate mental models about what and when and how they should eat after a workout. Things I have believed or heard from others at various points in my life include:

  • "If you're trying to drop weight, it's better not to eat after a workout because you don't want to cancel out any of the calories you just burned."
  • "If you just burned 800 calories, you're fine as long as you don't eat more than 800 calories."
  • "You don't want to replace ALL the calories you burned, so if you burned 800, you should only eat like 400."
  • "I just burned 800 calories which means I can eat 400 calories' worth of ice cream & it'll be the same as if I burned 400 calories & ate nothing!"
  • "It's important to refuel but be sure to use 'good' carbs like fruits, vegetables, etc., not 'bad' ones like bread/sugar/etc., which will just make you fat because they process too quickly & spike your blood sugar."

I am not going to go through & debunk all that, because hopefully, after I've shared what I learned from Dr. C., you will completely understand why none of those statements have any basis in reality.

To Refuel or Not To Refuel?
We started by listing out my weekly workouts in broad categories (from most to least exhausting: long run, speed workouts, tempo/threshold runs, karate, short easy runs, and strength workouts). Then, based on my description of each, he estimated how many calories I was burning per hour and what percent of it was carbs versus fats, then used that to calculate (about) how many carb calories I burn in each type of workout. (Higher effort = higher percentage of energy coming from carbs. See this post for the details regarding why.)

(In Dr. C's spirit of keeping things simple, there's a lot of rounding to nice, easy numbers.)

Long Run Speed Work Tempo/Threshold Karate Easy Run Strength
per Hour
600 700 650 300 600 300
Duration 2-3.5 hours 1-1.5 hours 1-1.5 hours 1.5 hours 1-1.5 hours 45 minutes
Total Cals
1200-2000 700-1000 650-1000 300-450 600-900 220
%Carbs 65% 80% 70% 80% 65% 80%
Total Carb
Cals Burned
780-1300 560-800 450-700 250-350 400-580 170

Those carbs come first from blood sugar (glucose) and then from glycogen stores (first from muscles and then your liver). This means that after the workout, your blood sugar has dropped, which triggers your body to start cannibalizing muscle tissue in order to bring it back up to normal. (Breaking down muscle tissue releases amino acids which the liver can convert to glucose.) If you are an athlete, losing muscle tissue = bad news.

Also, some people who would like to lose weight mistakenly think, "If I don't eat post-workout, then I'll have that much larger of a calorie deficit, so my body will burn off more fat!" No. Your body cannot replenish blood sugar from fat. If you don't give your body carbs immediately after a workout, it has no choice but to cannibalize existing muscle. And since more muscle = more fat burning, this is really just shooting yourself in the foot. So that's the first reason that you *definitely* want to give your body some carbs right after your workout.

The second reason is that you need that glycogen replaced to fuel your future workouts (as well as life in general). If you don't replace it and just eat normally, the way you would if you hadn't done the workout, your muscles and liver will be underfed & carb-starved, making future workouts & other activities that much tougher (making it less likely that you'll get the full benefit of the workout). This is the second reason why you definitely want to eat carbs post-workout!

When To Refuel:
If you recall from the earlier posts, our bodies can generally turn carbs into glycogen (good) at a rate of about 1 gram per minute. Give your body carbs faster than that, and anything beyond that 1 g/mt just gets stored as fat you don't need instead of fueling muscles that do need it.

BUT, during exercise, our body's ability to process carbs & convert them to glycogen increases. It stays elevated for brief period after the workout ends, then quickly drops off (dropping by half every ten minutes, reaching baseline again after about half an hour). So, the best thing to do in terms of refueling your muscles and liver as effectively as possible is to take advantage of those first golden ten minutes post workout to refuel.

What To Refuel With:
Ten minutes is not a lot of time, which means you want to be rather choosy about what you eat. For example, in the past I had sometimes been refueling with fruit or a fruit/yogurt smoothie. The trouble with this is that a) fruit is just not that calorie dense and b) its carbs are only half glucose, which (long story short) means it's going to take the other half (sucrose) a lot longer to get to your muscles because of the way your body processes it. The result was that my liver & muscles were chronically under-fueled.

So. For the purposes of post-workout refueling, you want something a) calorie-dense that is b) mostly carbs and c) mostly glucose, for example, bread or crackers (the whiter the better) or a grain-based granola bar (little or no nuts/dried fruit). It could even, said Dr. C., be your favorite pastry! Sure, there may be a little sucrose & fat in there, but not enough to make much of a difference. Plus, the joy of having a favorite treat post-workout rather than, say, 2 slices of bread might make you more likely to have it consistently within that golden ten-minute window, which is the more important part. Apparently this is what he personally does. (I have personally been enjoying a slice of yellow cake with chocolate frosting this past week after my runs, leftover from Don's birthday. Don is not a fan of this new strategy of mine & thinks I need to get my own cake.)

Screw kale. THIS is literally the world's most perfect food.

I know this will challenge many people's existing beliefs of what qualifies as "healthy" eating and refueling. There is a lot of propaganda about how simple carbs/simple sugars/refined grains/etc. are "bad" and we should be "eating clean" and fueling with "good" carbs like fruits & vegetables. Many of us have internalized that propaganda so deeply that it's incredibly difficult to think about things in any other way. However, like most propaganda, those types of claims oversimplify the facts in the service of a snappy one-liner that looks good on a Pinterest board.

When you look at the science, it becomes clear that those are overgeneralizations. The fact is that no foods are always, categorically good or bad for you in every situation (barring medical conditions, obviously); it turns out that what is best for you to eat depends on the purpose you need that food to serve. (But again....that doesn't make *nearly* as pithy a sound bite as "EAT CLEAN TRAIN MEAN GET LEAN!!") When it comes to refueling, the purpose is to get a lot of glucose from your mouth to your muscles as soon as possible. A handful of crackers (or a piece of cake!) will serve that purpose. An apple will not.

How Much To Refuel:
This is where I think it differs a little from person-to-person. While I definitely don't believe I'm overweight by any stretch of the imagination, I do know that I raced better when I was a few body fat percent points lower, so Dr. C. has me shooting to replenish about 2/3 of the carbs I use during my workouts. If I were already at my perfect performance weight and wanted to stay at my exact body fat percent, then we'd probably instead be shooting to replenish all of it (since we'd be trying to protect that perfect amount of body fat & not risk falling below it).


Long Run Speed Work Tempo/Threshold Karate Easy Run Strength
per Hour
600 700 650 300 600 300
Duration 2-3.5 hours 1-1.5 hours 1-1.5 hours 1.5 hours 1-1.5 hours 45 minutes
Total Cals
1200-2000 700-1000 650-1000 300-450 600-900 220
%Carbs 65% 80% 70% 80% 65% 80%
Total Carb
Cals Burned
780-1300 560-800 450-700 250-350 400-580 170
Replace 500-850 350-500 300-450 150-200 250-400 100

(Again, rounding to nice numbers to keep things simple, generally downward since I'm above my best performance weight.)

No But Seriously, When:
If you look at the numbers that are here, and you think about that whole golden ten-minute goal, you may notice that there's a distinct problem in some cases. Have a little 100 calorie granola bar post-strength work? Fine. A handful of crackers and a nice slice of cake after a tempo run? Great.

But 850 calories' worth of bread/cake/granola bars in 10 minutes after a long run? If this seems insane to you, it's probably because you're a reasonably healthy, non-bingey eater.

I mean I certainly can't wolf down the better part of a loaf of bread in ten minutes, especially right after a long run. (Although, to be fair, I have known people who have no problem whatever devouring the entire kitchen the second they get back from a long run, soooo there's also that.) And even if I could, even with my body's elevated ability to process carbs into glycogen post-workout, 850 calories in 10 minutes is *still* going to be more than it can deal with & result in carbs I need for refueling going to unneeded fat instead.

So yes, start with the usual ~200 calories of fast-digesting carbs in those first ten minutes. Then, have an extra serving or two of carbs with your next meal (usually dinner for me), remembering to do 2x volume in crunchy veggies so you actually get those carbs. Finally, if you're still not there, add another small snack sometime later in the day (remembering that your carb-processing abilities will be back at baseline, so 100-150 calories' worth is about all your body will be able to do anything with unless you pull the crunchy vegetable trick).

Because he's all about the simplicity, Dr. C. made this handy chart for me:

Long Run Speed Work Tempo/Threshold Karate Easy Run Strength
First 10 Minutes 200 200 200 150-200 200 100
Add to Next Meal 300-400 150-300 100-150 N/A 50-200 N/A
Additional Snack 0-125 N/A N/A N/A N/A N/A
2nd Snack (or
add to next meal)
0-125 N/A N/A N/A N/A N/A
Total Carb Cals
500-850 350-500 300-450 150-200 250-400 100

(Note: "Add to next meal" means **in addition** to the normal ~50-100 cals or so of starches you'd have even if you'd done no exercise that day.)

So you can see that it's long run refueling that requires maybe the most thought and attention. The refueling is easier if you do the long run earlier in the day, because you can spread out the carb calories appropriately in order to ensure they get stored as glycogen and not fat. (From a refueling standpoint, you can see that it's significantly easier if you do the run before lunch, because then you have two meals left in the day where you can add good chunks of carb & veggies; I almost always do my long run after lunch, so if I do a particularly long run, I need to do two snacks spread evenly between dinner & bed. This is why doing long runs particularly late in the day is problematic in terms of making sure you get fully refueled.)

Another question I had for him, "What if I have my 200 carb calories snack right after, but I'm still reeeeaaallly rungry?" Answer: Either have your next meal right then (with the requisite veggies), or have another carbolicious snack, BUT that one has to be with 2x crunchy veggies. Basically he was like, sure, you can wolf down 8 granola bars if you want; just realize that without a bunch of fiber to slow digestion, most of those calories will get stored as fat.

For me, the next critical step was getting in my head what 100 calories of carb looks like, because there is no way I'm reading nutrition panels every time I need to eat something. So here are some specific examples he gave me, based on stuff I like to eat:

  • 100 calories: 1 slice bread (half sandwich); 10 Triscuits; 1/4 cup granola; 1/2 larger granola bar or 1 smaller one [the ones I get are I think ~120 calories]
  • 200 calories: 2 slices bread (a sandwich); 20 Triscuits; 1/2 cup granola; 1-2 granola bars, depending on size
  • 300 calories: slightly over 1 cup (cooked) of rice, potato, yam, pasta, couscous, quinoa, etc; 3 slices bread (remember to add 2x the volume in veggies to slow digestion)
  • 400 calories: see above, plus 1/3 cup extra (again, remembering to add the right amount of veggies)

So there you go. Refueling!

Next up: Okay, this is all very nice in theory, but how is it working out for me in real life?


  1. I'm loving all the info you've provided! And I think you've done a really good job at explaining it. I bet it's helped you to rehash all the info too!

    I am terrible at fuelling for my runs. I always run on an empty stomach - I run as soon as I wake up in the morning (and I have a 10 month old baby so I'm already sleep deprived) and then I have a coffee as soon as I finish my run but it's always ages before I actually get a chance to eat.

    I reckon I could manage to eat a banana in about 60 seconds pre-run, and throw something in the pram to eat immediately after too. I guess that's a goal to work towards!

  2. Huh! I'm really, really enjoying this series!

    Questions: I thought you were supposed to have protein after a run. Remember when chocolate milk had a lil moment because of it's supposedly ideal protein:carb ratio? Plus, most of the packages of "recovery" drinks I get from running stores emphasize the protein (and salt, and electrolytes, etc.). Is that not important?

    Second question: If carbs/sugar/glucose are what is important, would a glass or two of juice be a good thing to have? That seems easier to stomach after a speedwork session than a couple slices of bread; plus, it's more portable.

    1. Yeah, I actually want to ask him about this. I have a feeling that the point is just making sure you get a steady amount of protein over the course of the day and the lack of it being more of a problem than really needing it immediately after a workout, and he's sort of assuming, "Well if you do everything else we talked about, you shouldn't need more at that point." But I'm totally speculating.

      The juice thing occurred to me too. I would assume that anything that's glucose would work, and maybe liquid would be even better since it digests faster? I should ask about that too. I know a lot of juice is sucrose and I don't think that works.

    2. I had a similar question about sports drinks. I guess they're mostly sucrose and not glucose?