Slowing with Age?

We started our current diet 10 months ago in an attempt to regain our health and vitality and lose some of the weight that had crept on over the last few years. We appeared to be developing signs of metabolic syndrome despite our frequent hikes, and it was time for more drastic measures. We love the outdoors and hiking, so it was natural to combine hiking/jogging with the low carb diet we began last January. Initially, we did much the same routes as we’d been doing on our casual hikes for the last two years. We gradually increased the challenge of our outings, trying to find ways to connect different parks, no longer being satisfied with the ~8–11 miles available in most parks. At first, these longer outings seemed long and took a lot of time: 12, 15, 18 miles. I experienced my first nausea during and after an 18-mile run/hike (with a couple of thousand feet of elevation change). That just made me mad and I wanted to tackle it again, this time with a bit of food to see if the nausea could be prevented (it worked). Then on a whim, we did our first 50K (Headlands 50K—cool but very hilly), and got seriously addicted to ultra events and pursuit of improved fitness. The first was slow (8.5 hr), which again made me mad and determined to do better. The second (Stevens Creek 50K—see Mark Tanaka’s race report) was worse for me at least (9.5 hr, but very hot and hilly, very low finish rate), though David tolerated the heat much better and did quite well (~7 hr). The third was getting better, but still unacceptably slow (Skyline-to-the-Sea: 7 hr, and net downhill. See Scott Dunlap’s race report). Our fourth ultra was the Firetrails 50-miler which took 12 hours (at least, not a slower pace than previous races; see Jean Pommier’s race report ). Undeterred, a couple of weeks later I ran 49 miles (again in 12 hours at the SF One Day—another painful story).

So why so slow? I’m 52 years old, and seem to have lost much of whatever speed I ever had (a middle of the pack sprinter in high school and college). I was on track for a 3:20 marathon before a calf injury slowed me down—PR of 3:27), now 25 years ago. Just how slow must I be now? Is it possible for a person to regain the health and vigor they had when they were younger? This is the grand experiment, and may fail badly, but that’s the question. Can I get back what I once had? Can I get better? Do I have to be resigned to being old and slow? Can I improve my health while I do it?

So it seems it’s time for some more serious training. We’ve started doing small interval workouts on the track (a few 200s, 400s and 800s) and some tempo runs, just to try to jog the memory of those quiescent fast twitch muscles (no pun intended). I was dismayed to realize that I’ve lost all sprint speed, and running up on my toes feels like I’m going to spazz out and fall on my face. Just doing 400s at an 8-minute-mile pace seems fast at this point. I’m hoping that will change, but how to improve?

Recently, I came across a link to a blog I haven’t discovered before, with an interview with Dr. Maffetone about training for endurance events that was quite interesting. He’s the inventor of the 180 rule (basically subtract your age from 180 to calculate your maximum aerobic heart rate [HR]). According to this method, you train at a level that achieves the desired HR, and you naturally speed up even though you maintain this level of effort, as you train your body to use fat as fuel. In the interview, he describes how he discovered this method basically by measuring respiratory quotients to determine at what HR fat burning occurred as opposed to carbohydrate burning. According to Dr. Maffetone, anaerobic training can be implemented after base aerobic training, in interval workouts or races, then followed by more base training.

I was intrigued and read some of the other advice on his website (sign up for a free membership). His nutrition advice really surprised me as well—another low carber of sorts! He advocates cutting out all refined carbohydrates, much the same advice of the cardiologist Dr. William Davis who is working hard with his patients to prevent and reverse their atherosclerotic disease.

It’s possible that we’ve already achieved a good grounding in aerobic (fat burning) ability, and that now would be a good time to work on speed. Maybe a good test would be to run a regular road marathon to at least get a good baseline number on my starting point. We’ll have to see how it goes…

Carbohydrate Needs of the Endurance Athlete

There is increasing recognition among endurance athletes that at least some fat and protein consumption is beneficial for athletic activity extending beyond about 3 hours. Further, most athletes understand that increased protein consumption post-event is valuable for speeding recovery and reducing discomfort in the following day or two. But most still insist that you
absolutely need plenty of carbohydrates before, during, and after the activity to achieve peak performance, to avoid “crashing” or “bonking,” and to recover quickly. Aid stations are typically stocked almost exclusively with carbohydrates, especially sugars (jelly beans, cookies, M&Ms) and simple starches (potatoes, potato chips, pretzels, gels), with the addition of some limited fats and protein only in the longest events. I’d come to increasingly suspect that this advice is probably wrong, and especially wrong for anyone who has adopted a low-carbohydrate diet and made the physiological adaptation to fat-burning to fuel exercise. I can now add my own anecdotal experience.

I have been restricting my average carbohydrate intake to an estimated 20% or so of calories for about 10 months now. At the same time I have been increasing my exercise level and capability substantially, to the point where I have now completed several 50K running events and one 50-mile event. At first, running seemed harder without the usual high level of carbohydrate intake, but over a few weeks it got steadily easier until fairly suddenly it was much easier. I was able to run uphill again (which I hadn't been able to do for a while); I found my routine breathing rate during comfortable sustained running had slowed by at least a third; I could easily go longer without any food intake besides water.

Nevertheless, for my first 50K event, I consumed more like a 50% carbohydrate meal the night before, and consumed the usual assortment of provided aid station food, avoiding only the simple sugars. The running went well enough, though my weight jumped a few pounds the next day and took three or four days to return to “normal.”

Since then I have been steadily cutting back on carbohydrate supplementation during the run. I did the 50-miler on mostly protein and fat with only a modest amount of carbs thrown in. Then I tried a strict low-carb 50K run, using only a “protein shake” (my own brew of whey protein, soy protein, milk, cocoa, almond meal, and walnut oil) for the entire distance. It worked great! I had steady energy throughout the event (no ups and downs) and was still feeling strong at the end to the point where I did not participate in the post-event food and was happily running around on the beach where the event ended. (The day-after weight gain still occurred; apparently that's not a carbohydrate effect.) So my conclusion is that all this carbohydrate is not needed for successful endurance!

There’s still a question of peak performance. Do you need the carbs and the associated blood glucose spike to do your absolute best? Can you go faster with carbs than without? Does it matter if you’re planning short events (sprints, strength events, etc.) rather than longer endurance events? I don’t know, but I’m increasingly favoring the hypothesis that you don’t actually need much carbohydrate at all once your body is adapted to using fat as its primary fuel.

There are at least a handful of papers related to this topic. These papers all support the idea that only limited amounts of carbohydrates are necessary or even desirable for endurance athletes. See, for example:

Larson-Meyer et al., “Effect of dietary fat on serum and intramyocellular lipids and running performance,” Med Sci Sports Exerc. 2008 May;40(5):892–902 reports 3-day crossover trials of endurance trained runners with low fat (10% fat LFAT) or medium fat (35% fat MFAT), and concludes that “despite approximately 30% lower IMCL [intramyocellular lipids] 0.220±0.032% LFAT, 0.316±0.049% MFAT; P = 0.045) and approximately 22% higher muscle glycogen stores at the start of performance testing (P = 0.10), 10-km performance time was not significantly different following the two diet treatments.” Lipid profiles suggestive of cardiovascular disease were associated with the high-carbohydrate-low-fat diet, and the authors concluded that “even short-term consumption of a low-fat diet may unfavorably alter serum lipids, even in healthy, endurance-trained runners.” (Note that this study did not allow time for adaptation to the different diets, so glycogen and lipid levels in the muscle cells are due only to the acute diets tested);

Vogt et al., “Effects of dietary fat on muscle substrates, metabolism, and performance in athletes,” Med Sci Sports Exerc. 2003 Jun;35(6):952–60, which studied the effect on trained athetes of a high-fat (53% fat) or high-carbohydrate diets (17% fat) for 5 weeks in a randomized crossover design, found that maximal power and vO₂-max during an incremental exercise test to exhaustion were not different between the two diet periods, total work output during a 20-min all-out time trial (298±6 vs 297±7 W) on a bicycle ergometer as well as half-marathon running time (80 min 12 s ± 86 s vs 80 min 24 s ± 82 s) were not different between HF and LF. Blood lactate concentrations and respiratory exchange ratios (RER) were significantly lower after HF than after LF at rest and during all submaximal exercise loads. The authors concluded that “muscle glycogen stores were maintained after a 5-wk high-fat diet period whereas IMCL content was more than doubled. Endurance performance capacity was maintained at moderate to high-exercise intensities with a significantly larger contribution of lipids to total energy turnover”;

Lambert et al., “High-fat diet versus habitual diet prior to carbohydrate loading: effects of exercise metabolism and cycling performance,” Int J Sport Nutr Exerc Metab. 2001 Jun;11(2):209–25. No changes were observed in circulating glucose, lactate, free fatty acid (FFA), and b-hydroxybutyrate concentrations during exercise. However, mean serum glycerol concentrations were significantly higher [indicating mobilization of fat stores with glycerol release] in the HFD-CHO trial. The HFD-CHO diet increased total fat oxidation and reduced total CHO oxidation but did not alter plasma glucose oxidation during exercise. By contrast, the estimated rates of muscle glycogen and lactate oxidation were lower after the HFD-CHO diet. The HFD-CHO treatment was also associated with improved time trial times (29.5±2.9 min vs. 30.9±3.4 min)[150 min cycling at 70% vO₂-max followed by a 20 km time trial] for HFD-CHO and CTL-CHO. They conclude that “high-fat feeding for 10 days prior to CHO-loading was associated with an increased reliance on fat, a decreased reliance on muscle glycogen, and improved time trial performance after prolonged exercise”;

Leddy et al., “Effect of a high or a low fat diet on cardiovascular risk factors in male and female runners,” Med Sci Sports Exerc. 1997 Jan;29(1):17-25, which notes that “restricting fat intake may compromise endurance performance and that increasing fat intake may improve endurance performance,” and concludes that “a 42% fat diet maintained favorable CHD risk factors in female and male runners whereas a 16% fat diet lowered Apo A1 and HDL-C and raised the TC/HDL-C ratio”;

Horvath et al., “The effects of varying dietary fat on performance and metabolism in trained male and female runners,” J Am Coll Nutr. 2000 Feb;19(1):52–60, which concludes that “runners on a low fat diet consume fewer calories and have reduced endurance performance than on a medium or high fat diet [and] a high fat diet, providing sufficient total calories, does not compromise anaerobic power.”