Human Performance vs Survival: Carbohydrates for peak performance

I want to get this off my chest right now, the low fat, high carbohydrate diet was/is possibly the worst idea ever. I think it’s a safe assumption that, as well, that our shift to low fat high carb foods, not to mention the products that were developed for it and our general addiction to sugar has played a large role in the exponential increase in obesity world-wide, with America leading the way. The high carb diet has also been a major stimulus for much of the nonsensical claims made by Atkins and Paleo proponents. In this final installment of my Paleo series, I intend to dismantle the argument that primitive societies didn’t consume or rely on carbohydrate, including processed grains, as well as show how and why carbohydrate before and during exercise enhances performance, or why it’s absence hinders performance.

Grains, the building blocks of civilization and conquest

Many people have drawn erroneous conclusions that primitive man never ate grains, and/or chose to avoid sugar. In fact, looking at our sugar craving indicates that man has had the craving, just not the access. Humans are drawn to sugar, and most contemporary primitive societies introduced to coke, like it. Sweet sense is an advantage and lack of carb leads to diminished performance. In reality, grains, usually in the form of bread, have been eaten for at least 30, 000 years, and bread has served not only as a staple at the table, but also part of ceremonial custom for many religions. Moreover, carbohydrates have long fueled militaries throughout history from the Mayan’s who built an empire on Quinoa and potatoes, to Washington’s army, as well as our own military today.

I continue to struggle to understand how Paleo purists maintain such a myopic view of the historical record. As I noted above, society was actually built on carbs, as most primitive societies settle down in a region and began selectively growing indigenous grains, along with vegetables, and raising livestock. The American Indian relied heavily on a variety of heirloom corn. Sustained military campaigns have often had the greatest difficulty providing sufficient calories to troops, with carbohydrates usually lacking; Dr. John Castellani, from the U.S. Army Research Institute of Environmental Medicine, described one such example during the Revolutionary War which I’ve briefly summarized below:

American troops were charged with moving cannon from Fort Ticonderoga to Boston. Troops were already low on rations, in particular the standard biscuit, and forced to travel through uncut forests. Though hunting excursions yielded large game, troops continued to report lethargy and underperformance for the heavy labor required to transport the cannon.

Here we see the difference between low level/intensity activity (hunter/gather hunting runs) and sustained labor, which included intermittent high-intenisty work (military operations, or athletic competition). It is also important to note that glucose is the only fuel that can be used by the brain. However, if you’re reading this article you’re likely an athlete, so if we look to controlled research we see clear and convincing evidence for carbohydrates to not just sustain, but improve performance.

Understanding the sugar advantage

When assessing effectiveness, we must consider the activity intensity and the relative goal for performance. Are we just finishing or finishing fast? We often mistake Paleo as being out to win, but winning was about sustained endurance, not the fastest performance. The former is survival and requires little special fueling, the latter is performance and is maximized by carbohydrate. In relation to the latter, far too many papers have been published to review here, so I have chosen some representative studies that I’ll briefly summarize below.

Febbraio 00

In this paper, Febbraio and colleagues (including John Hawley, one of the world’s leading exercise scientists) endurance trained men (VO2 max ~63, which is very good) perform a 120 min of endurance cycling followed by a maximal time trial lasting 30-50 min (see below). They convincingly showed that eating about 2 g/kg of (~140 g) carbohydrate 30 min before exercise with or without (2 g/kg/2 hrs) carb consumption during exercise significantly reduced time trial times. Looking at the two extremes of carbs before and during vs no carbs before or during (ie, Paleo man), the carb group finished nearly 20 min faster!  Just as interesting, though, was the fact that eating carbs either before or during was still clearly better than the Paleo man strategy; carbs before and during appeared better, but not from a statistical standpoint.

Hargreaves 04

In this review, Hargreaves, Hawley, and Asker Jeukendrup (one the leading experts on fueling for endurance) compiled numerous studies to not only show that carbohydrate consumption not leads to better performance, they also debunk the “fat-loading” myth that burning more fat equates to better performance. Bottom line, if you want to go faster in endurance events, consume carbohydrates.

Peltier 11

Here’s a good example of a study that appears to show interesting results, but fails to answer their actual question. The authors were looking at the impact of carbs, BCAA’s, and caffeine on 2 hr running performance, and saw that compared to a flavored water drink, the combined drink improved running performance about 2%. The problem is that while they had a good controls in the study, the 2% improvement certainly is no better than carbs alone; actually, noting the Febbraio study, the final TT performance was improved nearly 50%! Now a caveat here, is that Febbraio used a final maximal time trial (a preferred performance marker in these types of studies), where as this study used only endurance time (more variable). The take home message? Water alone is a poor companion for long-term endurance performance; 2% amounted to about 400 m.

Atkinson 11

Here is a population based, correlation study, examining carbohydrate intake 5 days before and during the 2009 Flora London Marathon; finish times ranged from 2:43:41 to 7:20:20. In addition to nutritional data, they also looked at training volume and marathon experience. I really like this paper because it brings lab research to the field and uses a wide range of participants. Here are the major relevant (to nutrition) findings of the paper:

  • Lower body mass equates to faster running times; we already knew this, but its worth repeating.
  •  Runners who consumed >7 g carb/kg the day before the race ran significantly fasted across all training variables and race times; ie, carb loading the day before improves run times.
  • Runners who consumed >7 g/kg the day before were better able to sustain their run speed throughout the event.
  • Carb consumption immediately before or during did not appear to influence race times. This appears to contradict the Febbraio paper until we recognize that Febrraio used a standard high carb diet 24 hrs prior to their trials across a fairly homogenous study population. Furthermore, they again utilized 2 hours of activity followed by a maximal end time trial, as opposed to a more steady effort throughout.

The important conclusions that should be drawn from the above representative research is that abstaining from carbs during important events is a recipe for slower performance. One thing not covered here specifically, however, is intermittent activity, like soccer or repeated sprint activities. I will say that research that I have read support carb consumption here, well. None of this, however, addresses the impact of long-term (months to years) high carb consumption on overall health. If you’re like me, carbohydrate intake should be dictated by training volume, intensity, and performance goals. Most individuals simply do not require a diet that is continuously high in carbs, making carb cycling (eating more carbs as needed) optimal. Finally, I want to highlight the fact that there is NO CONVINCING EVIDENCE that consuming a high fat diet improves performance; the ACSM annual meeting has never dedicated any talks to the merits of high fat diets as superior for performance. I invite anyone to find me a reputable exercise physiologist who would recommend not consuming carbs during prolonged exercise.

My recommendations

Based on the current research here are my tips for carb consumption:

  1. Determine your ultimate goal! If you’re training less, or you’re training slower, reduce carb consumption 4-5 g/kg/day is probably sufficient, or ~50%.
  2. Eat carbs DURING intense sustained (> 1 hr) training; rule of thumb: if a great workout is your objective, fuel like a race! Likewise, if you’re training hard back to back days, like at a training camp, feed the beast!
  3. Eat carbs after training, particularly intense training. Let your hunger dictate your intake, and do not mix quality training with weight loss. You’ll end up with half-assed results for both.
  4. Estimate your carb needs for the event; rule of thumb: 1 g/kg/hr is a good start. Some people can tolerate up to 1.3 g/kg/hr, but experiment first!
  5. Practice your race fueling during training sessions that are most like competition.

Well that’s it for my survival vs performance series. Be on the look out for the upcoming companion Tipcast, and please feel free to comment!

Written by

3 Comments to “Human Performance vs Survival: Carbohydrates for peak performance”

  1. Luke Meers says:

    Great article. Have you seen any relevant articles which address the idea of “train low, race high”? To me, the concept that generally fuelling your body for optimal performance when training makes sense, but the idea of training the endurance adaptations of the body via restricted carb or calorie consumption is an interesting idea.

    • Tradewind says:

      Hi Luke,

      Yes, I have. I’ll actually be covering this topic this month, as I’ve gotten a few questions related in some way to this or training fasted. The short answer is that the findings are not conclusive, but they are interesting. I believe there is merit to them, and I practice this myself. If we consider the cost to benefit ratio, the cost of this is low (ie, if it doesn’t work, what harm does it do?), but the possible benefit is at least modest. The data indicates that there is an improved muscle response (eg, mitochondria produced, endurance enzymes). My caveat, though, is when you need to train hard, fuel like a race!

  2. Matt Stehr says:

    You are making 2 assumptions about the “paleo diet”:
    1. It is intended to improve performance. Not true.
    2. It is low carb. Also not true.
    I think almost anyone in the Paleo community would agree that while many athletes will experience some performance boost on a paleo-type diet, that is not the general intent. Paleo diets are useful for improving blood sugar and insulin regulation, putting autoimmune disorders into remission, improving overall health and longevity, and weight loss. Most Paleo experts would not recommend the type of “chronic cardio” that you suggest requires increased carbohydrate intake as this type of exercise is frequently seen as detrimental and certainly not ancestral (as you yourself have pointed out). Most of the Paleo folks that I listen to recommend increasing carbohydrate intake as your activity level increases.
    Paleo is also not strictly a low-carb diet. Paleo refers to the removal of grains, legumes, and dairy. By removing most grains you will indeed end up with a lower carb diet than what most Americans consume. However, groups like the Kitavans lead a hunter-gatherer lifestyle and get 70% of their calories from carbs. Paleo is macronutrient agnostic and does not recommend ratios of carbs, protein, and fat; it does require us to eat real food and get our carbs from fruits and starchy tubers (primarily) rather than from breads, pastas, and gels.
    Regarding your quote from the doctor at USARIEM, no doubt most Soldiers would be fatigued if only consuming lean wild game and performing a lot of physical activity. No doubt they also were not fat-adapted and their biscuit consumption resulted in horrible dentition and suboptimal health.
    Regarding the studies you quoted, all of these athletes were accustomed to a high carbohydrate diet and were not fat-adapted. I predict that in the future research articles will show that athletes who are fat-adapted can perform at a very high level while negating many of the negative effects of a high-carb diet. Will carbs increase performance in these individuals? Likely they will, but these athletes will experience improved overall health as a result of restricting their carb intake compared to the athlete who relies on carbs for every workout.
    Lastly, your statement about the brain only being able to use glucose as a fuel source is inaccurate. The brain can also use ketone bodies as a fuel source, or at least the folks at Princeton think so: