Anyone who has had anything to do with me, or followed my writing and work, will know that I’m an advocate for eating less carbs, more good fats and – most of all – eating natural, real food. I’m certainly not the first proponent of such ideas and I’m most definitely not the only one encouraging runners, multisporters, rowers, desk drivers and everyone in between to eat this way. The most appropriate question now then is, why? Why eat less carbs, more fat and why make sure they’re in the form of natural, whole foods wherever possible?
Let’s get back to performance. There’s no denying that it’s super important, and that performance is the common denominator for most athletes who approach a new dietary method or some facet of dietary intervention, such as supplements. Beyond all of the noise and extraneous crap that gets perpetuated throughout social media and the like, scientific research is the vehicle with which we ultimately pick up or put down these dietary interventions. As the science evolves and tells us more about old supplements, new supplements and indeed entire methods of eating (like paleo, vegetarian of LCHF), we develop more certainty in our decisions.
Or do we?
A very recent research publication by world-renowned Australian exercise nutrition professor, Louise Burke, provided some strong conclusions that the hardcore LCHFers are struggling to swallow. Dr Burke and her team at the Australian Institute of Sport completed one of the most rigorous and well-designed studies yet to be published on LCHF eating versus higher-carb methods and how they affect aerobic performance in athletes.
I encourage you to follow the reference below and have a read of this study. Put very basically, the researchers fed groups of 9-10 elite race walkers with diets of either primarily high-carb food, periodised high-carb or low-carb high-fat for three weeks. During this time, the athletes continued intensive training while many variables were measured pertaining to their oxygen capacity (VO2peak), fat oxidation and overall race walk performance. The LCHF individuals were the only group to experience a statistically significant impairment of performance in their 10km race walk times, compared to performance increases in the higher-carb eating groups… Shock! Horror! And remember, this study has been applauded for its design and execution.
Does this mean that we do away with LCHF if we’re in endurance sports? Should we go back to our pasta bakes and loaves of bread?
I certainly won’t be, and the reason comes back to the bigger picture I talked about earlier. There is so much more to my life and the lives of all of the athletes that I work with, than the times we achieve on race day. Daily energy levels, sleep patterns, immunity, the cultural aspects of food and the enjoyment involved with sourcing, growing and preparing it, to name a few.
While Dr Burke’s study is a strong one, it has some limitations when we attempt to draw applicable conclusions. For example, is three weeks really enough time to give keto or low-carb a go before throwing it out due to a lack of performance gain? What about the qualitative data; how did the athletes feel while eating this way? What kind of foods did they eat? And herein lies the difficulty with such tightly controlled scientific studies; the conclusions can lose applicability in the real world.
Some of you might also find it interesting to hear that Dr Burke has previously suggested that the paleo diet is not necessarily healthy because it leaves out grains. Burke qualifies this by saying that fortified grains are how we get a lot of important micronutrients, as if there’s no other fathomable source of such essential nutrients. Sounds to me like someone who has had their head buried so far in the proverbial sand that is researching and dissecting foods and information, for so long that they’ve lost touch with the power of real, whole foods to nourish and heal.
Another very recent publication by a team of New Zealand researchers followed five multisport athletes for 10 weeks on an extreme LCHF dietary regime; a ketogenic diet. The study is far less scientifically robust than Burke et al; it had fewer participants, no control group and less control over many variables that would affect the outcomes, to name a few differences. This New Zealand study did, in fact, conclude that performance was mildly decreased across the board, just as the Australian study showed. This wasn’t the major conclusion, however. The authors summarised that the athletes were keen to pursue a modified LCHF diet moving forward because of the unexpected health and wellbeing benefits that they all experienced throughout the 10-week intervention. So, while their performance was not improving (yet), these individuals were feeling so much better than before that they prioritised health and wellbeing over everything else. That, right there, is the bigger picture.
It’s also very meaningful to state that these studies were only three weeks and 10 weeks in duration, respectively. There are many reasons why a study would only last so long, money being the major one (a randomised controlled trial like the Australian study can cost somewhere in the millions). Most LCHF experts (and non-experts) will tell you that adapting to a high-fat diet can take a lot longer than that, particularly if you’re talking about exercise capacity or performance and not just blood markers that show you’ve switched to ketosis. For what it’s worth, there are anecdotal reports coming out of the NZ high-performance sport facilities (and elsewhere around the world) suggesting that with longer-term fat adaptation (i.e. months and years), athletes aren’t just experiencing improved health, they’re seeing big gains in performance, too.
The studies we’ve compared here – despite investigating the same thing – are very, very different. One is disproportionately more robust than the other, and as a result is published in a scientific journal that is significantly more recognised and has a much further reach. The point is though, that the practical application of such information is really up to the reader. I am suggesting that with eating LCHF, there is much more to the story than performance alone. Additional to this, the generalisation of these studies’ results is limited. It is becoming ever more pertinent that, while strong study designs can indicate trends over a specified period of time, individual case studies are actually quite applicable and useful. That is, experimenting with an individual (rather than a large group all doing the exact same thing) is very useful for determining the overall advantages or disadvantages of a way of eating. We are all very different and we process and utilise foods accordingly. Some of us work best on a larger proportion of protein than others, and some can operate completely on fats. It is my conviction that beyond these individual variations, as a society right now we are all eating more carbs than we ever should have been. Therefore, every one of us could do with shifting towards a little more healthy fat and a few less carbohydrates, regardless of what you “run best on”.
Burke, L. M., Ross, M. L., Garvican‐Lewis, L. A., Welvaert, M., Heikura, I. A., Forbes, S. G., ... & Hawley, J. A. (2017). Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of physiology, 595(9), 2785-2807.
Zinn, C., Wood, M., Williden, M., Chatterton, S., & Maunder, E. (2017). Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes. Journal of the International Society of Sports Nutrition, 14(1), 22.
Science of Ultra Podcast. Episode 19