With the Marathon des Sables (MdS) a few weeks away, now is the time to sort out your race food. This article highlights two critical elements to give consideration in deciding how much of what to take. The key points are extracted from an article I wrote after the MdS 2013 and was compiled from research I conducted during the 2013 MdS.
In this article I will deal firstly with how much calories to take and secondly briefly discuss the current trend in terms of protein, fat, carbohydrate composition.
The objective, of any multi-stage ultra-endurance runner participating in a self-sufficiency race is to find the optimal calorific count. Achieving optimal calories guarantee that no excess weight is carried and that your food energy input is sufficient to ensure that your performance is not impaired.
The first element that became clear from the 2013 research is that the conventional basal energy calculation method of determining your specific energy requirement overinflates your actual energy requirement by about 30% to 40%.
It is worthwhile noting that every person is unique and that your specific energy requirement may differ from the figures presented here, however, there is a high probability that you could fall well within the averages presented here. As always, any element of your kit, food, or strategy need to be tested during a long distance (I recommend 30km’s plus) prior to your race.
During the research I tried to find a way to present the calorie requirement in a more practical way. The very broad approach of listing calories per day seemed somewhat problematic as you usually end up with the same calorie requirement for a 28km and a 50km day. This can’t be correct so I reconceptualised it in terms of body weight (in kg’s) and daily distance (in km’s).
From the research the following spread of calorie requirements emerged:
The absolute minimum came to 0.81kCal’s per kilogram of body weight per kilometre distance for the event (from now on I will abbreviate this as kCal/kg/km). This can now be reworked to align calories per day by taking the daily distance into consideration. The absolute maximum came to 1.27kCal/kg/km. Bothe the absolute minimum and maximum saw a sharp decline in performance. On the one hand the calorie count was simply too little to sustain adequate and consistent performance while on the other hand the calorie count simply presented too much, meaning that an athlete were carrying too much redundant weight.
The range that emerged from the research data as presenting the best balance between sustained performance and calorie intake fell between 0.87 and 1.09kCal/kg/km, with 0.91kCal/kg/km emerging as optimal.
Again, from the research the following spread of calorie requirements emerged:
The absolute minimum came to 0.43kCal’s per kilogram of body weight per kilometre distance for the event (from now on I will abbreviate this as kCal/kg/km). This can now be reworked to align calories per day by taking the daily distance into consideration. The absolute maximum came to 1.14kCal/kg/km. Bothe the absolute minimum and maximum saw a sharp decline in performance. On the one hand the calorie count was simply too little to sustain adequate and consistent performance while on the other hand the calorie count simply presented too much, meaning that an athlete were carrying too much redundant weight.
The range that emerged from the research data as presenting the best balance between sustained performance and calorie intake fell between 0.63 and 0.95kCal/kg/km, with 0.78kCal/kg/km emerging as optimal.
Fat / Protein / Carbohydrate Composition
The top 10 runners in the MdS field had a 55% Carbohydrate, 25% Fat and 20% Protein diet during the race, whereas the top 300 runners had a 55% Carbohydrate, 20% Fat and 25% Protein diet. Weight wise both these groups would have weighed the same. The remaining runners seemed to have stayed with the conventional breakdown of 67% Carbohydrate, 8% Fat and 25% Protein. I personally don’t think that the composition itself has a substantial impact on runner performance. I am of the opinion that it is a matter of personal physiological preference. One runner processes protein more efficiently while another processes carbohydrates more efficiently. My main reason for this view is that there seems to be no significant difference between vegetarian, vegan, omnivores and carnivorous running diets, however, most vegan and vegetarian diets are predominantly carbohydrate based. My own experiment with a vegetarian diet proved this; however, there was a significant psychological impact for me as a carbohydrate rich diet just never seemed to satisfy me and I was hungry most of the time, which means that I was eating constantly. But again this was me and it might be totally different for other runners.
There are, however, one area where a carbohydrate rich diet impacts negatively and that is on weight. With a generally acceptable calorific density of 9Cal’s per gram for fat and only 4Cal’s per gram for carbohydrates and protein your composition can have a meaningful weight impact.
Taking the two main approached above and assuming a 2,000kCal per day for both the weight impact is as follows:
80% (55%+25%) of 2,000kCal’s is 1,600kCal’s weighing around 400g, and 20% of 2,000kCal’s is 400kCal’s weighing around 44.4g. This runner will carry roughly 444.4g’s worth of food per “day” which would translate to 3,111g’s (please note that this excludes packaging etc.).
75% (55%+20%) of 2,000kCal’s is 1,500kCal’s weighing around 375g, and 25% of 2,000kCal’s is 500kCal’s weighing around 55.6g. This runner will carry roughly 431g’s worth of food per “day” which would translate to 3,017g’s (please note that this excludes packaging etc.).
92% (67%+25%) of 2,000kCal’s is 1,840kCal’s weighing around 460g, and 8% of 2,000kCal’s is 160kCal’s weighing around 17.8g. This runner will carry roughly 478g’s worth of food per “day” which would translate to 3,346g’s (please note that this excludes packaging etc.).
Although this might seem insignificant the example is aimed at demonstrating the effect your choice on composition has. A carbohydrate rich diet weighs 329g’s more than the fat rich diet and this translates into an increase in weight of around 11%.
Food is a very personal element and should be tailored to your specific preferences. What you decide to pack for your race will not only have to sustain your body, in-terms of your race objectives, but will also play a significant role in your overall psychological state. If you have any specific questions feel free to post your questions here, or contact me via e-mail. You may also find the original article here.
One last remark, do read the race rules pertaining to nutrition and in specific whether powders, gells etc. are accepted as part of your calorie count.
Thank you for reading this blog, and good luck with the final preparations,
Genis and the push2extreme team.
kCal and Cal is often used interchangebly when nutritional values for off-the shelve food is presented. For the sake of this article and in response to some readers comments I corrected this article as follows; (1) kCal will now mean 1,000 (one thousand) calories.
The use of commas denotes thousand and the use of a full stop represents a decimal number.
In response to a question about calorific dencity of fats, proteins and carbohydrates, here is the accepted breakdown. 1g of fat contains 9cal, 1g of protein contains 4cal, 1g of carbohydrate contains 4cal.