By: Bob Seebohar, MS, RD, CSSD, CSCS, METS II
Low carb, high carb, no carb. It's a pretty confusing area of sports nutrition for cyclists right now. Since the advent of my Nutrition Periodization concept in 2004, cyclists have mostly adopted aligning their daily nutrition to support their training demands. As the kilojoules (KJ's) and training stress increase, then a shift of macronutrients (carbohydrate, protein, and fat) is needed to support physiological adaptation. The opposite is also true: lower training load and KJ's and restructure the daily nutrition plan to account for this. Seems pretty easy, at least until the low carb, high fat craze came into the picture.
There have been some interesting research studies published in the past few years, mostly because there are so many athletes trying these dietary strategies. I can say that from my experience working with all types of endurance athletes, a controlled carbohydrate nutrition plan is definitely beneficial but there are many "it depends" regarding how, when and why to do this. A one-size fits all structure should not be adopted by any cyclist. As I mentioned previously, it is very important to keep in mind that you will need to periodize your nutrition throughout the year based on your training cycle shifts. That is why I promote the concept of carbohydrate control rather than a full-on low carb/high fat daily nutrition plan. If you weren't an athlete, you wouldn't need to cycle your macronutrients to accommodate your training but then again, you wouldn't be reading this article so let's dig a bit deeper into this concept.
As I mentioned, there have been quite a few research articles published about lower carb/higher fat diets. I have chosen one in particular to highlight in this article to prove a few points and hopefully shed some light on this topic relative to answering your question, "what should I eat?" At the end of the day, I know this is the question athletes want answered, but often times researchers aren't focused on that, but rather in publishing data.
As I dig into evaluating this research study, keep in mind a few things:
- Research is often times a few years behind what we do in the field with athletes. This is mostly due to the long process that it takes to have research approved, the actual research process and then submission to journals for publication.
- The conclusions of research studies often grab the attention of media and as such, these are the only highlights that are communicated with athletes. It's really not fair. A good example of this was a research paper I reviewed to include in my Metabolic Efficiency Training Specialist certification a few years ago. It was a fat adaptation study performed on a small group of male cyclists who were fed different daily diets (standard, higher, and lower carbohydrate). The conclusions stated that there was no performance benefit during a 1-hour time trial with a lower carb/higher fat diet. Interestingly, I looked at the raw data in the results section of the research study and lo and behold, I found that there was an 11% improvement in power for the fat adapted cyclists for the time trial. How could this be? Easy. The results were not statistically significant, thus the researchers could not report the real-life results in a peer-reviewed journal.I don't know about you but I would take an 11% increase in power during a 1 hour time trial any day!
- One of the most important things to keep in mind is that there is no real definition of a "low" carbohydrate diet. A nutritional ketogenic diet is usually defined as eating 20 grams or less of carbohydrate per day but I don't know any cyclist that can pull off being in nutritional ketosis for an extended period of time during training. A "low" carb diet in research terms ranges from 10-30% of total daily carbohydrate intake.So again, what is low carb?It's a bit hard to compare a "low" carb diet if we do not have a standardized definition.
Now onto the research study. The title of the study is, "Manipulating carbohydrate availability between twice-daily sessions of high-intensity interval training over 2 weeks improves time-trial performance". It was published in the International Journal of Sport Nutrition and Exercise Metabolism in 2015 (volume 25, pages 463-470).I chose this particular study because it 1) was performed on active but not elite cyclists (as some studies are, thus it is hard to extrapolate the data to recreational athletes), and 2) it replicated what may happen sometimes to recreational cyclists in-between training sessions during a work day (that is, the inability to properly feed due to work constraints).
Eighteen cyclists (9 male, 9 female), with average VO2 peak of 44+9 ml/kg/min and age of 21 years, were recreationally active, exercising 2-3 times per week without structure or sport specialization. They maintained their normal daily diet before and during the study and did not take any dietary supplements.
They were separated into two groups: HI-LO (received low carbohydrate between intervals) and HI-HI (received high carbohydrate between intervals) and trained a total of 6 days over a two-week period. Each subject performed identical high intensity training (HIIT) sessions twice per day on research days with a 3-hour recovery in between. It was during this recovery that the nutrition was manipulated to be high or low carbohydrate. Before each session, participants ate their normal breakfast.
The training sessions consisted of a 2-minute warmup at 50 watts followed by 5 sets of 4 minute intervals at 60% of their peak watts (found in baseline testing), interspersed with 2 minutes of rest. After the first training session was complete, the subject received either 17 grams of carbohydrate, 1 gram of protein, and 3 grams of fat (HI-LO group) or 195 grams of carbohydrate, 15 grams of protein, and 5 grams of fat (HI-HI group). Muscle biopsies were performed before and after the tests to provide muscle data.
What did the researchers find? It's quite interesting actually because for years, we have touted the need for eating foods higher in carbohydrate if we had two-a-day training sessions within 16-24 hours of each other to enhance glycogen repletion and speed nutritional recovery. This was the first study that showed a short-term application of the "train low, compete high" carbohydrate paradigm can actually enhance whole-body exercise performance (not just an isolated muscle). Their data supports that training with low carbohydrate availability (in this case, between HIIT sessions in the same day), improves performance.How much you ask? The HI-LO group improved from 211 to 244 watts (+33 watts) and the HI-HI group improved from 203 to 219 watts (+16 watts). Quite an improvement that recreational cyclists could benefit from in the real world of training and racing!
Of course there are always challenges with research studies, due to the constraints the researchers normally have with studying human subjects. Could these confound the results? Perhaps. Here's a short list of the challenges I found:
- Subjects were young and relatively untrained (and not cyclists). We know that elite cyclists' physiology responds differently to dietary and training manipulations.
- There was no mention of what their normal daily diet consisted of.High carb, low carb, high fat? This could be a huge confounding variable. While diets were controlled throughout the study, we just don't know their normal intake of macronutrients.
- The researchers mentioned that fitness was improved throughout the study so the question begs, "to what degree was the improved performance due to nutrition versus training?"
Overall, this study shows promise with carbohydrate controlling techniques relative to training periodization. There are still many unanswered questions regarding how long to implement this and what training cycles are more or less appropriate to try this, but at least we are closer at understanding that cyclists can indeed improve performance by paying closer attention to the foods they eat after a tough interval session instead of acting as garbage disposals. Keep this in mind the next time you have a higher intensity training session and you think you need to stuff your face with a lot of simple sugars. That just may not be necessary.
Bob Seebohar, MS, RD, CSSD, CSCS, METS is a sport dietitian, exercise physiologist, strength and conditioning specialist, and elite triathlon coach. He traveled to the 2008 Summer Olympics as the U.S. Olympic Committee Sport Dietitian and the personal Sport Dietitian for the 2008 Olympic Triathlon Team.
Bob's book, Metabolic Efficiency Training: Teaching the Body to Burn More Fat, teaches athletes how to structure their nutrition and training program throughout the year to maximize their body's ability to use fat as energy and improve body composition.He also has a Metabolic Efficiency Recipe book in electronic format with over 100 metabolically efficient meals and snacks. For more information and to order the books, visit www.enrgperformance.com or email him at email@example.com.