I read an article today by Carmichael Training System on the use of Ketosis for athletes and felt compelled to respond. The article is not entirely off base, but I think that the decision to consider any diet is an individual one. The athletes that come to CTS aren't necessarily indicative of the general population. Diets are lighting rod conversations and I am not trying to suggest this diet is superior for everyone, just presenting an opposing view based on experience.
Before responding to the points in their article, a quick bit about me. I am a former football player turned adventure junky (runner). There is nothing spectacular about me as a runner. My best mile time is basically 6:00 flat. I weigh about 195 pounds at a relatively lean 13% body fat, hardly an endurance build. I am a relatively large, aging athlete with a family history of high blood pressure and type-2 diabetes. Yet, I am a self-coached athlete that has managed to go sub-24 hours at Western States and qualified for Boston (3:09:55). Having tried to train and race for both health and performance and both using high-carbs and high-fat, I think I have an educated opinion on this topic. I have read the research and walked the walk. That said, I don't believe this diet for everyone. Individual factors -- age, body composition, etc... -- may sway someone to consider this diet or leave it.
After years of experimenting with many diets, including Atkins, I converted to LCHF in February of 2014. I was coming off knee surgery and unsure of what to expect once I returned to racing. Somewhat unexpectedly, my racing took off and I have had an incredible run of races the past three years, without changing much about the way I train. I have found that I need far less fuel on the run and that I recover much better from races on LCHF. What's more, I am not obsessed with eating during ultras and my energy levels are more consistent, though I still have highs and lows. Perhaps the best thing for me is that my blood pressure has dropped significantly (20 pts) and my blood markers are impeccable (particularly my triglycerides and HDL).
KETOSIS DOESN’T IMPROVE ENDURANCE PERFORMANCE
I have to say I disagree with this point. This might true if you look at lab results of indicators that we use to approximate performance, but in the field I don't know that this is true. My best races have all come since I converted to LCHF, everything from marathons to 100 mile races. I attribute this success to eating less during training and races: not being consumed mentally by a nutrition plan, no GI distress, more constant energy, less muscle wasting. Low carb by itself did not improve my V02 max, but it sure makes racing ultras simpler.
A good friend of mine -- a much more typical endurance (build) runner -- ran the Leadville 100 two years in a row. The first year he suffered horribly from a rotten gut and nausea. A year later, without training appreciably different, he ran two hours faster and finished 4th overall (18:43). He attributes nearly all this success to a paleo/LCHF diet which freed him from having to eat so much. Athletes such as Zach Bitter, Tim Olson, Jeff Browning, and Jason Schlarb have all used similar approaches with great success. (Jason Schlarb's post-RRR interview in 2013 was the "aha" moment for me.)
KETOSIS MAY PREVENT GASTRIC DISTRESS
Chris Carmichael was listing this as a positive, and I agree. This really gets at the heart of what I was saying above. Jason Koop, whom I respect very much, thinks the gut can be trained. I agree with this to an extent. Athletes have limited opportunities to train the GI system for a race that is likely more than double the length of their training runs. And, each day and each race offers something different whether it be altitude, heat, etc... There is no limit to the amount of "specifity" to train your gut for: taking a gel on a big climb, having certain products after 12 hours without real food, etc... I ran the Leadville 100 as my first 100 as a high carb athlete, eating an impressive 10,000+ Kcals (nearly 400/hr). Overall my experience was positive, but I definitely had issues with diarrhea in the second half. Converting to LCHF, I now eat more like 5000 Kcals in a race and my gut thanks me. My nutrition plan is quite simple and I can typically carry 5-6 hours of my preferred products with me at a given time.
Also, at a certain point, you have to ask if this is the right idea. Endurance sports are demanding and there are lots of questions marks about long term health on the heart as well as just the physical wear and tear. So we are all paying a bit of an unknown price. That said, is eating these products all day to train and race the best thing? The Boston Marathon race director has heart disease.
WEIGHT LOSS FROM DIETARY KETOSIS IS PRIMARILY FROM CALORIC RESTRICTION
This shouldn't be the case if done properly. I eat the same, or more even, on LCHF. Each gram of fat has more than twice as many calories as gram of carbohydrates. Eating half the volume would yield an equivalent amount of calories in one's diet. Perhaps the issue is that the athlete finds the diet too limiting (more on that later) and just eats too little involuntarily. It can be a chore to eat enough fat to keep your macronutrient ratio at 75+%. I regularly eat oils to keep my ratio high enough. The majority of the weight loss should come initially from water as the athlete's muscles dump glycogen (and the associated water) and later from fat burn. One difficulty here is the body composition of the athlete -- leaner athletes may struggle to convert their fat stores to energy.
One last thing, there is a difference between nutritional ketosis and fasting/starving ketosis. Unless you a purposely fasting, athletes should be trying to stay in nutritional ketosis. As for me, I was only in ketosis for a few months and switched to LCHF instead, allowing myself "strategic" carbs. I get plenty of benefits from the higher fat burning overall improved gut.
COMPLIANCE IS A MAJOR BARRIER TO SUSTAINING KETOSIS
This point I very much agree with. Ketosis is black and white and therefore very difficult to maintain in our western culture. That is the reason I consider myself "LCHF" and not in ketosis. A typical training day for me consists of fewer than 75g of carbs -- often strategically planned around hard or long workouts -- and I occasionally cheat. However, the closer I say to ketosis recommendations, the better I feel. More importantly, when I am keeping strictly with the diet, my blood suggests my body is in superior health.
KETOSIS IS A COMPETITIVE DISADVANTAGE
While I understand the author's point, I disagree. While exercising, the body is more tolerant of carbohydrates without bumping you out of ketosis and it actually makes you more flexible. And, you could easily take the opposite side of this point of view -- what if you need carbohydrates and get lost? What if your crew gets lost and the aid stations don't have high-carb products you've trained your gut with to avoid GI distress? As a low carb athlete, I regularly go hours without eating with zero fear of a "bonk". When I ate carbs regularly, I was obsessed with my next feeding interval and hitting that 300-400 Kcal/hr mark.
My experience with LCHF has been very positive and I encourage all athletes, particularly larger ones or those with family history of diabetes, to try it out. People in the LCHF community often say each of us is an experiment of one. There are likely aspects of this diet that can help anyone. The points in the CTS article are all worth considering, but I hope I have given a point of view from someone that has used the approach successfully.