BEST DIETS FOR ATHLETES
Our metabolic system is remarkably flexible in its ability to use a variety of dietary macronutrients as fuels. Traditionally, carbohydrate-focussed diets have been recommended for participation in sports and carbohydrate loading prior to competitive events has been the main nutritional strategy for improved performance on the day.
However, in recent years, this strategy has been questioned and there are many research projects that have been undertaken to find whether high fat/low carb diets or high carb/low fat diets are best for endurance athletes. You may ask, why do we want to know? The human body has a very limited capacity to store carbohydrate – approximately 5g of glucose in circulation and between 100g-500g of glycogen in muscle. That’s enough fuel to keep us running/cycling/swimming for one and a half hours. That’s why we have to focus on getting carbs in on a regular basis via food, gels, drinks etc. during long course events such as marathons and iron man competitions. On the other hand, a person of average weight has around 10kgs of fat on their body – enough fuel to allow them to complete 30 plus marathons. It would make sense that we would want to access this big pool of unlimited energy in endurance sports.
There is always much debate amongst sports dieticians, nutritionists, physiologists etc. about what diet is best for each sport, but I work quite differently to that. I don’t agree with a sport approach, but more on an individual approach. For every research experiment where an athlete has done better on a high carb approach, there is another who did better on a high fat approach. Setting one dietary regime for an entire sport is discounting us all and our individual needs. Genetics, body type, training routine, metabolic health, blood sugar response, gut health etc all have a major part in the way we metabolise food so how could one size fits all?
When working with endurance athletes, fat adaptation is a factor that is always at the forefront of performance management. Symptoms such as constantly being hangry, getting hungry an hour after eating, feeling dizzy and completely exhausted after training etc. can suggest blood sugar imbalances and insufficient fuelling during training. Often, when these symptoms occur, an athlete will up the carbs and gels to offset, which can often make things worse. When we eat a lot of carbohydrates, our body responds with insulin, which clears glucose from the blood. If carb intake is too high, insulin can be magnified a few times and you actually end up hypoglycemic as it clears too much glucose from the blood. If this happens a few times a day and you are constantly carb loading, you may end up with a condition called insulin resistance, whereby the cells become numb to the action of insulin, and glucose can’t get into the cells. In the meantime, you have a big pool of energy in your fat stores that is largely being ignored.
As well as noting symptoms, I also use the ECAL test to assess how fat adapted the athletes I work with are. When we burn fat, we don’t sweat it out, we breathe it out. By analysing our breath after a 4 hour fast, the ECAL machine can inform us if we are burning fat or glucose. Ideally, we should be burning 80% fat for energy at this point. If the test shows that we are constantly looking for glucose then we know that dietary changes are required such as periodisation of low carb diets, then high carb diets, reducing the carbohydrate load in the diet on an ongoing basis, doing some training sessions fasted etc. Some athletes perform better on high fat, low carb diets but I like to use the phrase carbohydrate appropriate diet whereby carbs are in the diet but they are amazing, high fibre carbs and will help to keep blood sugar balanced, and our fat stores are still on the radar.
The fuelling we put in our mouth is important for sports performance but so is the fuel we have stored on our body. Being able to access that fuel at the appropriate time may provide the winning edge.