Carbenflarb: Fact and Fiction About Fats and Carbs

Nowhere in the world of running is there more confusion than over the matter of carbs. Despite decades of research, questions abound: How much? How often? What kind? Consulting the running literature, we find a smorgasbord of advice, anecdotes, and conjecture.

Okay – let’s rap about carbs. We won’t try to arrive at any quick conclusions. We’ll simply amble through the vast carb lore. Perhaps we’ll arrive at some general principles we can apply to manage our carb intake. And we’ll linger around a particularly interesting issue.

In the early 1970s, a West German physician, Dr. Ernst Van Aaken, devoted tireless energy in support of women’s marathoning. Dr. Van Aaken organized the world’s first all-women’s marathon, which was held in his hometown, Waldniel, on October 28, 1973. (Christa Vahlensieck won in 2:59:25.6.)

Van Aaken coached Harald Norpoth, the 1964 Olympic silver medalist in the 5000 meters. Later, he wrote a book about his training theories, The van Aaken Method, which was translated and published in 1976 by Runner’s World. A cornerstone of the method was van Aaken’s belief that doing long runs without carbs improves the body’s ability to burn stored fats. Van Aaken believed this gave marathoners an advantage, by sparing the body’s limited carbohydrate supply.

Arthur Lydiard advanced the same theory – Olympians Peter Snell, Murray Halberg, and Barry Magee completed their weekly 22-miler carb-free. Lorraine Moller, a Lydiard disciple and 1992 marathon bronze medalist, told me she avoided carbs during 20-mile runs in her competitive years, and that she generally finished those runs at 6:00 pace, feeling fine.

However, in her autobiography, On the Wings of Mercury, Moller reports that the Lydiard-trained athletes weren’t carb-shy when they weren’t running. And in Healthy Intelligent Training (an outstanding guide to Lydiard’s ideas), Keith Livingstone reveals that the after-run carb binges of the Lydiard elites were epic. A local buffet owner finally had to beg the runners to stop coming in after their long runs, because they were eating him out of business.

Which raises the question: were those runners’ bodies “learning to burn fat,” as van Aaken and Lydiard claimed, or were they learning to stockpile carbs? Hard to say.

There is evidence that the body can run extremely long distances on fats alone, given the right metabolic catalysts. A commercial product called Vespa, named after the Asian Mandarin wasp (Vespa mandarina) from which its main ingredient is extracted, enabled the women’s winner of the Rio Del Lago 100-mile event to consume just 1000 carb calories during her race. That’s powerful evidence that fats can fuel the long run. But whether that ability can be trained without throwing wasps in a blender, isn’t clear. (See a user review of Vespa here.)

The fueling guidelines on Hammer Nutrition’s website cite research showing it takes fewer carb calories to stoke the fat-burner than was formerly believed. Most vendors of “race drinks” still urge us to replace all the carbs we expend while we run. But it seems that’s a mistake – according to Hammer’s reviews of the research, too many carb calories overwhelm the body’s ability to absorb them, with counter-productive results and a risk of digestive upset.

Hammer’s recommendation is conservative – take no more than 200-300 calories per hour; just enough to keep the furnace burning, adjusted to individual needs.</p

Years ago, I wanted to lose weight rapidly, and I began doing my long runs carb-free. It was a complete disaster – although I did lose lots of weight, my 3½-hour long runs turned into death marches. I shudder to remember how I dragged my whimpering body through those runs, a brain-dead emotional zombie.</p

At the time, I couldn’t figure it out. After all, I was eating a ton of fruit – typically, six oranges, several apples, and half a banana per day. But when I counted calories, I realized that it takes 16 oranges to replenish the calories burned in a single 10-mile run. Obviously, fruit wasn’t doing the job.

Opening my copy of Lore of Running, I learned that the body never runs out of carbs, even when it’s starving. As author Tim Noakes, MD explains, that’s because the body’s most carb-hungry organs are the brain and heart, and the brain always holds back sufficient carbs to keep those organs running. When I went carb-free, my body simply shut down my peripheral muscles, forcing me to run on empty. I was burning a high proportion of fats, all right – and it wasn’t pretty.

I was inadvertently following the Atkins diet, which, by restricting carbs, aims at forcing the body to burn fat for energy. The lousy feelings that accompany carb-free eating account for the diet’s rapidly declining popularity. I was experiencing ketosis, which the Wikipedia defines as “a state of the organism characterised by elevated levels of ketone bodies in the blood, occurring when the liver converts fat into fatty acids and ketone bodies (which can be used for energy as an alternative to glucose).

A blonde was terribly overweight, so her doctor put her on a diet. “I want you to eat regularly for 2 days, then skip a day, and repeat this procedure for 2 weeks. The next time I see you, you’ll have lost at least 5 pounds.”

When the blonde returned, she shocked the doctor by losing nearly 20 pounds.

“Why, that’s amazing!” the doctor said, “Did you follow my instructions?”

The blonde nodded. “I’ll tell you, though, I thought I was going to drop dead that 3rd day.”

“From hunger, you mean?”

“No, from skipping.”

I wonder if it’s significant that none of Arthur Lydiard’s elite athletes report enduring the kind of agony that I suffered while they ran carb-free. I suspect this may be because they weren’t actually “running on empty” – that their carb-rich diet gave them sufficient carb “kindling” to get them through those runs feeling reasonably good. Lydiard urged his athletes never to run to exhaustion, but to finish ever run feeling “pleasantly tired.”

Also, Lydiard’s runners had trained for many years before they began running 22 miles without added fuels. And there’s also at least a possibility that their bodies were predisposed from birth to manage carbs efficiently. This may yet another way in which the elite athletes’ bodies are very different from the average person’s, as sports science tells us.

In Running: The Athlete Within, renowned sports physiologist David L. Costill states that carbs are essential for recovery:

When subjects eat only as much food as they desire, ad labium [per appetite], they often underestimate their caloric needs and fail to consume enough carbohydrate to compensate for that used during training or competition. This discrepancy between glycogen use and carbohydrate intake may explain, in part, why some runners become chronically fatigued and need 48 hours or longer to completely restore muscle glycogen. Runners who train exhaustively on successive days must consume a diet rich in carbohydrates to reduce the heavy, tired feeling associated with a deficit in muscle glycogen.

So, that might be part of the explanation for why we experience “good days and bad days.” If your energy supply is low, some of the muscle fibers you most frequently call on to generate the force for running may fatigue easily or may not develop the…tension you expect. Consequently, you may sense that it takes more effort to run at a given pace than when you are rested and have plenty of muscle glycogen.

Of course, we all know that a baked potato and an ice cream sundae are no cure for the bone-deep fatigue that follows a grueling effort such as a marathon. Recovery always takes time – and for major efforts, it takes longer. Dr. Costill says:

We have observed that seven days after a marathon race in which muscle glycogen dropped from 196 to 26 mmol/kg of muscle, a normal diet and rest restored the glycogen only to 125…. We have recorded similarly slow glycogen restoring after exhaustive treadmill running…. Although the cause has not been fully explained, the muscle trauma which occurs in distance running may inhibit the mechanisms normally responsible for the uptake and storage of glucose by the muscle.

To recover quickly and feel good in your next run, be sure eat carbs. Oh, and be sure to run high mileage, or any carbs not stored as muscle glycogen will make you fat.

A former training partner, Carl Ellsworth, won the northern California USATF road race series in the 60-65 age group three years straight. Carl trained 100 miles per week, and he said the best thing about high mileage was that he could eat as much as he liked. Carl’s body carried no extra fat.

Yet, strangely, Carl took no fuels during the marathon. As he explained it, “I’m only out there three hours.” Is there an as-yet-undiscovered relationship between marathon finishing times, running efficiency, individual differences, high-mileage training, and carb requirements? Who knows? I do know that Carl Ellsworth guzzled carbs after each run, starting with heavily sugared lemonade.

The hard-training Kenyans eat a carb-rich diet. From Run to Win: The Training Secrets of the Kenyan Runners, by Jürg Wirz:

According to the ICEARS [International Center for East African Running Studies] study, the daily carbohydrate intake of elite distance runners in the United States and the Netherlands has been measured at 49 and 50 percent of total calories, a far cry from the Kenyan total of 76.5 percent. The Kenyans appear to do a far better job in fueling themselves for their very demanding training.

Like the ultramarathon-running Tarahumara Indians of northern Mexico, the Kenyans get their carbs primarily from corn.

Because I sit at the computer all day, weight-gain is a concern, and so I’m always learning about weight-management and diet. I can gain 10 lbs by spending five minutes in the same room as a baked potato.

In a nutshell, here’s what I’ve learned about how we gain weight.

When we eat, Mr. Digestive Tract looks at the incoming mess and diverts simple sugars, saturated fat, and starchy carbs to a special, high-speed tube that goes straight to Mr. Gut and Mrs. Butt.

It’s a simple but physiologically accurate image for understanding weight-gain. Those three foods in particular – fats, starchy carbs, and sugars – pose the greatest danger for runners who want to stay slim.

In fact, we can construct a very effective weight-loss plan around those three “danger foods.” In my experience, the weight simply pours off if I eat a ton of salad and steamed veggies, a ton of fruit, a ton of beans, a moderate amount of nuts (almonds are great, as they don’t convert easily to body fat), and “just enough” carbs and eggs, dairy, and meat.

The body does need carbs, and the athletic body definitely needs saturated fats. But it only needs “just enough” – thus, the key factor is knowing how much is plenty.

An excellent book that documents this dietary approach with a rigorous review of the research is Eat to Live, by Joel Fuhrman, MD. Fuhrman shows that green vegetables in particular are a tremendously effective weight-loss aid, because they supply the two factors that most effectively kill appetite: bulk, and high nutrient content.

As you can see, our meandering trip through the lore of carbs has enabled us to arrive at few conclusions. That’s probably because the logical mind is very good at taking things apart, but less adept at seeing the whole picture. A better guide, for the practicing athlete, is experience, combined with calm, unprejudiced inner feeling. So let’s apply common sense to the question of carbs.

Take the notion of carb-free 20-milers. Is that something we really need to do, in order to train our bodies to finish a marathon without bonking? I don’t think so. For starters, today’s race drinks do prevent the marathon bonk. (Hammer Nutrition’s Sustained Energy is particularly effective, in my experience.)

Second, it may be a serious mistake to erode or destroy the inner enjoyment of the long run in order to slog along carb-free. What’s more desirable: to get a solid training effect by running 20 miles at our optimal long-run pace, or to slow to a crawl for the sake of training our fat-burning ability?

Third, research at the Heartmath Institute shows that positive feelings enhance physical performance. As Frank Shorter put it, people get more out of their training when they enjoy it.

Africans start running, mostly slowly, and then they accelerate. For them, it is a kind of a game. You try to challenge the other. If you want to be successful, you have to enjoy your training. When you take it too seriously, it damages your thinking and puts you down. But if you go and say, okay, it is a game, man, let’s do it, it’s fun – then you will not use a lot of mental strength. – Mike Kosgei, Kenyan national coach, 1985-1995, 2001-2004

Speaking personally, I’ve made a conscious decision to use carbs on my long runs. I love the long run. It’s pure recreation, a highlight of my week. And I take pains to preserve that enjoyment. I’m not remotely interested in staggering through the final miles in limp-home mode, even if it might, someday, somehow, improve my endurance in the marathon. On the other hand, of course, I don’t care to cram carbs in excess of metabolic needs and pack on the pounds. The key, to my way of thinking, is balance – taking “just enough.”

As I mentioned earlier, most days, I eat a fairly low-carb diet. So I do need to take carbs to fuel the long run. Several hours before the start, I’ll eat a handful of dates to carry me through the first miles. Then, perhaps 60 minutes into the run, I’ll begin taking ClifShot gels. Some days, I’ll need only a single 100-calorie gel per hour; more commonly, I’ll need two or three per hour. The criterion is to take just enough to maintain good energy and avoid the low-carb staggers. On tough hills, I may need more.

By consuming carbs, am I training my body not to burn fat? That is, am I spoiling my body by feeding it a luxury diet of carbs? I doubt it. I’m certainly not taking enough carbs to replace the calories burned during the run. If I cover, say, 6-7 miles per hour, I’m burning 600-800 calories. Yet I’m taking only 200-300 calories from gels. So, again, it seems I’m giving my body “just enough” to keep the fat-burning flame alive, without letting my body burn only carbs.

For about four years, up to three times a month, I ran/walked 30-35 miles as part of my training for ultramarathons. And I completed those runs almost entirely carb-free.

At the time, I was eating a diet that was higher in carbs than now, because I had a physically demanding job. During those 6- or 7-hour runs, if the course was hilly, I would take one bite per hour of a protein/carb bar, but if it was flat I took no fuel at all, just plain water and electrolytes.

So, it is possible to cover very long distances at a slow pace, without taking carbs. However, I wouldn’t recommend it.

Although I felt fine during the runs, my recovery was gruesome. It took four days before I began to feel remotely human again. Karl King, an ultrarunner and chemical engineering professor at the University of Michigan, explained to me that not taking carbs during runs longer than about 2 hours increases the body’s production of the stress hormone cortisol, resulting in delayed recovery and premature aging. Karl said he’d noticed that runners who ran carb-free looked older than their years.

During flat runs, I ran 5 minutes and walked 1 minute, and on hilly runs I walked the uphills, ran the downhills, and did 5:1 on the flats. For those four years, I was exercising 6-7 hours up to three times a month carb-free. Yet when I stopped running ultras and returned to running 20 miles straight through, I still bonked at 17-18 miles unless I took carbs. My body hadn’t learned to burn fats efficiently.

It could be argued that my fat-burning ability would have improved if I’d run 20 miles straight through without carbs.

But I see no value in doing long runs that way. The results are questionable, the experience isn’t fun, and I’ve never seen research showing that running carb-free, in fact, improves fat metabolism over the long term. I wonder if it wasn’t simply a logical-sounding idea that van Aaken and Lydiard propounded as fact.

6517_3I once translated a research paper by Ernst van Aaken, on the possibility that distance running helps protect against cancer. When I showed it to Ralph Paffenbarger, MD, a leading exercise researcher, he told me it was interesting, but not supported by research, and probably just wishful thinking.

For me, the more interesting issue isn’t about carbs, in any case – it’s about ways of knowing. Science has helped us enormously by showing us how carbs work in the exercising body. Yet I wasn’t able to arrive at a satisfactory system for managing my own carb intake by only following science and logic. Rather, I learned from my own, direct experience.

I tinkered with various ways of carbs until I found what produced the most “expansive” results – defined as what felt completely right. From my own experience, combined with calm, dispassionate feeling, the answer became clear.


Running Times just published an article, “Running on Empty,” that presents evidence in favor of carb-free training. Have I changed my views? Not a bit. I didn’t find the studies cited in the article terribly convincing. I was left more than ever persuaded that training carb-free is a waste of time, and possibly even dangerous (because it increases the stress hormone cortisol in runs longer than about 2 hours). As I stated above, when I trained for ultras, I could easily cover 31 fairly flat miles without taking carbs at all; yet the recovery was terrible, and my endurance didn’t increase noticeably more as a result, than if I had taken carbs.

On the other hand, I’m having excellent results nowadays, using moderate carbs (one 100-calorie gel every 30 minutes) during long runs of 2 to 2.5 hours. Also: it’s good to remember that Lydiard’s runners who trained carb-free did ferocious carb-reloading after their 22-milers, and ate a very high-carb diet.

Additionally, the Kenyans cited in the RT diet for their “low-carb” running actually eat a very high-carb diet when not training – up to 60 percent higher in carbs than typical American distance runners, as reported in Juerg Wirz’s book, Run to Win: Training Secrets of the Kenyan Runners. My conclusion: these runners were hardly running “carb-free”; rather, they ran very heavily carb-loaded.

Finally, I’m happy with my present way of handling carbs, which is to eat very little starchy carb during daily life in order to keep my weight manageable. That’s another reason why I eat carbs while running. And, again, when I tried running (and living) on a drastically low-carb diet, my long runs immediately turned into death marches. All this tells me that the “carb-free long runs to increase fat-burning” is bogus, especially as the RT article notes that Meb Kefzleghi, who trains “carb-free,” takes large amounts of carbs during his races. (So why bother “training fat-burning metabolism,” which is stressful and can be unpleasant, at least in the last miles of long runs?)