This entry is a response to a post by the good folks over at Stronger, Faster, Healthier. They are a company that I do truly respect; I promote the heck out of their high-quality fish oil (and use it myself) and I admire the commitment they have to putting out excellent products amid a sea of imitators. It is my sole desire to create an open dialogue here, and not to attack or disparage them in any way, and I hope that readers will keep the same goals in mind when commenting.

An athlete at our gym sent me tweet last week saying that he was now uncertain whether or not he should be eating sweet potatoes post-workout, based on what he read on the Stronger, Faster, Healthier blog (the post in question is here, do not read further until you read it first). It’s a well-known fact that I promote starchy carbs (sweet potatoes, taro, squashes, etc.) post-workout in order to refill glycogen spent during intense exercise (like CrossFit). It’s something that has worked very well for me personally, as well as for my clients. So I was naturally curious to see what SFH had to say on the topic. Sadly, it left me disappointed.

“In order to understand glycogen re-loading, one needs to know a little biochemistry.”

We definitely agree on the mechanisms for glycogen synthesis and I definitely agree that the increased insulin sensitivity that comes from exercise is sufficient to transport nutrients where they need to go in that 30-60 minutes post-workout window. But that’s where the agreement stops.

The next section serves to vilify insulin spiking. On the whole, I tend to think excess insulin spiking post-workout is largely unnecessary, and most of the bodybuilders out there who are doing it are quite insulin resistant already, which is why they need a huge insulin spike to transport nutrients into cells. But do I think a short-term rise in insulin in a 30-minute to 2 hour window is a bad thing? No, as long as those insulin levels return to normal, which they do when eating an anti-inflammatory diet based around whole, nutrient dense food. The claim that

over-stimulating insulin after exercise becomes a pathophysiologic risk factor for follow on heart, vascular and inflammatory disease

lacks proof and incorrectly creates the assumption that the risk factors due to chronically-elevated insulin levels (as seen in metabolically deranged individuals) occur with the same frequency and magnitude in individuals who are only spiking insulin post-workout. The statement is comparing apples to oranges; the physiological state of chronically-inflamed, metabolically-deranged people is completely different from healthy, Paleo -eating, hard-training individuals.

The above image is incredibly misleading. The implication here is that a single serving of sweet potatoes will spike insulin more than whey protein, and that is simply untrue. Whey proteins in general spike insulin.  As a part of milk, that insulin response is needed so that animals can shuttle as many amino acids into the body as possible for growth. And studies, like this one, have shown that whey is incredibly insulinogenic (again, not necessarily a bad thing in an acute setting), so don’t pretend for a second that whey is some white knight compared to a sweet potato. It makes no sense to disparage an insulinogenic food in order to replace it with something that is also insulinogenic, but a non-food.

Furthermore, the goal of eating sweet potatoes is not to spike insulin. It is to replace glycogen that has been depleted during exercise. Not replenishing muscle glycogen can lead to serious side effects, namely burning off liver glycogen, then brain glucose, which can lead to a shutdown of neurons firing, which I don’t have to tell you is a very bad thing. Think about your body as a hybrid car, where the gasoline is your glycogen/carbs and the electric system is your fat stores. When you’re cruising around town (light runs, light weightlifting) you can be in electric (fat oxidation) mode and do just fine. But if you need to accelerate hard (CrossFit, hard runs, sports) you have to use some gas (glycogen/carbs) because the electric system can’t keep up on it’s own. Continue to try accelerating without any gas in the tank and you either aren’t going to go anywhere or your car is going to breakdown. If you aren’t refueling yourself with good post-workout carbohydrates, you will burn through your glycogen and your health and gym performance will suffer. A great anecdote is provided by Mat LaLonde, as a guest on The Paleo Solution podcast (minute 44). Also worth mentioning is that continual glycolitic work done on a low-carb diet has the potential to elevate cortisol to unmanageable levels. This can lead to a state of constant stress which leads to fat retention and adrenal fatigue. Bottom line: if you’re doing glycolytically-demanding work, you need to eat glucose to replace spent glycogen.

Now, SFH claims that “At Stronger Faster Healthier, we emphasize energy regeneration as a first step,” but the subsequent sentences about ATP depletion, near-death in cells, and their “ATP package”, lead me to think that there is a disconnect between the product they are selling and how our bodies actually work during exercise. There are three energy systems in the body: Phosphagenic, Glycolitic and Oxidative (Aerobic). These systems work in beautiful concert to provide you with the energy you need for your workout. The statement that

After a workout, cellular energy (ATP) is depleted. Our cells are at a low energy state and in some cases just able to survive while stores of ATP build back up.

is a severe exaggeration. The entire purpose of the Phosphagenic pathway is to make use of ATP in a quick burst and then have the Glycolytic pathway continue producing ATP from glycogen stores. To say anything other than this without sufficient proof is to be disingenuous to the science of metabolism and exercise. And seriously, if your cells are in the near-death state they describe, go see a doctor, as that’s the kind of cellular behavior seen in folks with severe insulin resistance or cardiac disease.

To summarize, our bodies, after a rigorous workout, are primed to burn fat. In fact having depleted the available glycogen stores, our bodies become fat burners. Now add back sugar and high glycemic carbs and our bodies switch back to sugar users and excessive insulin spiking. This is not a good plan.

I don’t even know what to do with this section. We’ve already established that depleting glycogen stores and leaving them that way is a bad thing, but depriving it of the moderate to high-glycemic carbs it needs to replenish those stores is just setting you up for further failure.

So what do they recommend after taking your recovery drink? An apple. This is not the best idea as excess fructose (yes a sweet potato has some fructose, but it represents less than 10% of the total sugars) like that found in most fruit upregulates glucokinase within the GLUT2 metabolic pathway and shuttles most sugar (glucose and fructose) to the liver first, since that is the only organ that can process fructose. That means when you should be filling up your muscle glycogen, you’re wasting precious time filling your liver glycogen first. Your recovery will really suffer if this happens.

The last sentence of the post is worth mentioning as well: “Avoid supplements that have excessive carbohydrates in them, especially after exercise when insulin sensitivity is high and our bodies are primed to over release insulin.” Yes, our bodies become more insulin sensitive post-workout, but it does not mean the we are “primed” to release more insulin. Rather, being more insulin sensitive means that your body needs to release less insulin to deal with the same amount of carbohydrates. So while you should avoid non-food supplements in general, avoid them because real food is a better choice, not because of insulin sensitivity.

So, what should you do after you work out hard, like after a run or a CrossFit WOD? Simple:

- Within 30-60 minutes, eat some lean protein (we don’t want fat to slow down digestion) and some starchy carbs.

- Make eating real food a priority

- Leave the fruit out of it.

- Bring it with you to the gym.

Your post-workout meal is your bonus meal for all the hard work you did and all the muscle you’re going to grow. Don’t underfeed yourself by making a normally scheduled meal your PWO meal; you need extra nutrition to support your training.

I encourage SFH to reply and clarify any of their positions or challenge any of my assertions. Ultimately, we’re both in the business of making people healthier and open discourse is very valuable in achieving that goal.

-TLC