In Season Performance is Built in Off-Season Work, Part III Phasing Nutrition with Training
It seems for the general public and the athletic population, nutrition can be confusing. Magazine articles and blogs advocate the next latest and greatest, silver-bullet diet. These are often extreme and present wildly different strategies. Generally, these diets lack context. There is no one-size fits all nutritional strategy, but the specific strategy must be individualized, based on the individual’s metabolism and goals.
Low Carbohydrate High Fat Diets
There has been a resurgence of high fat diets, initiated by the ultra-running community. Their objective is to more efficiently utilize on-board fuel stores in order to minimize caloric intake to help avoid GI distress (a common culprit for DNFs at ultra-running events). For this segment of athletes, who operate primarily at an aerobic intensity during their events, this nutritional strategy helps them achieve their objectives. In a study conducted by Burke et al. (2017), the authors state that the low carbohydrate, high fat (LCHF) diets do improve the ability for whole body fat oxidation and the aerobic base. These studies also suggest that LCHF diets reduce circulating glucose at rest and during exercises, and as a result, would benefit those trying to lose weight.
Julie racing cyclocross at the West Sacramento Grand Prix
However, for sports such as cycling, where in a race, the cyclist hits every intensity level from a 10 sec all out sprint to hours at endurance pace, this nutritional strategy does not work. While these LCHF diets have proven effective to improve fat oxidation they have also effectively down-regulated carbohydrate oxidation, i.e. the body’s ability to access carbohydrates as a fuel, when required for high intensity work. On strictly LCHF diets, the athlete experiences a decrease in high intensity sprint power, and an increase perceived exertion, heart rate and muscle recruitment. Additionally, LCHF diets increase oxygen demand, thereby reducing the efficiency in the transfer of metabolic power to mechanical power output.
For athletes, such as cyclists, the nutritional strategy must be individualized and periodized to match the demands of their training and racing. In this way, nutrition supports the intensity of the training or race, and ensures the proper adaptive response. There are energy pathways that are oxygen dependent, fats and carbohydrates and those that are oxygen independent, such as phosphocreatine and anaerobic glycolysis. Burke (2015) refers to metabolic flexibility, defined in the context of sports performance as ͞the ability to rapidly and efficiently utilize these pathways to maximize ATP regeneration.͟ Athletes, such as cyclists, whose events require the ability to operate at varying intensity levels, require metabolic flexibility.
Metabolic Efficiency Testing
At the Kaiser Sports Medicine Endurance Lab, we provide a test assessing metabolic efficiency. This test helps us understand how our clients are burning fuels and pinpoints each individual’s optimal fat burning zone, based on their unique metabolism. It clearly identifies if the client is burning the right fuel for the right intensity. We start this test at a very low intensity and incrementally increase the intensity (either via speed on the treadmill or watts on the bike) and monitor how fuels are used based on the respiratory exchange ratio. When we start the test, we would expect the client to be burning nearly 100% fats, and the ratio of fats to carbs to gradually adjust and mirror the increasing intensity. In this test we identify a cross-over point, the point at which the individual is burning 50% fats and 50% carbs. From this we determine, based on heart rate and intensity (pace for runners, watts for cyclists) the individual’s optimal fat burning zone. I find it interesting in this test, that that this zone differs greatly from individual to individual and rarely fits neatly in to one of the established formulas like, for example,percentage of max heart rate.
This client is burning carbohydrates at a very low intensity level and has virtually no fat burning zone
Recently, we have had several clients come in for metabolic efficiency testing, who prescribe to high intensity training (HIT), and are frustrated by plateaus in fitness and creeping weight gain. In these cases, we have consistently seen that these clients have a small to non-existent fat burning zone. This is often a symptom of both training and nutrition – training based primarily on higher intensity workouts with little to no endurance, and a carbohydrate rich diet. These athletes, in contrast to the ultra-runner, on the LCHF diet, have efficiently trained the high intensity fuel-source pathways, but have down-regulated the fat metabolism pathway.
This client is extremely metabolically efficient, with the cross overprint occurring at a relatively high power output
We have found by appropriately phasing nutrition with training, we can greatly improve metabolic efficiency and significantly shift the cross over point to the right.
Phasing Nutrition with Training
The athlete who depends on the ability to efficiently tap the right fuel for a range of intensities, can capitalize on transition season, a.k.a. off-season to improve their metabolic efficiency. Generally during this phase of year-round training, the focus is on general strength in the gym and developing a wide base of endurance, so the majority of the work is low intensity, aerobic. During this time of year, curtailing carbohydrate intake will force the body to utilize the right fuel for the right intensity, in this case metabolize fats for endurance work.
In both the Thomas et al. (2016) and the Burke (2015) studies, they discuss the concept of phasing nutrition with training to most effectively train the body to efficiently utilize the right fuel substrate for the right intensity. These studies also note that low carbohydrate and high fat diets, and in some cases fasted states, coupled with endurance training, will improve fat oxidation and the aerobic base. Thomas et al. (2016) further defines the benefits of training without carbohydrates or in a fasted state, to include increased mitochondrial enzyme activity or mitochondrial content. Burke (2105) also specifies that phasing nutrition with training should take place at the macro and micro level.
In transition season, the nutritional strategy can be managed from a more macro-level, but once we enter in to the preparation phase, which includes higher intensity work, nutrition needs to be micro-
managed to accommodate the range of intensity. For example, say you have a sub-threshold to threshold interval workout on Wednesday morning, you would eat a balanced meal on Tuesday night, Wednesday morning, and after the workout to ensure proper recovery. And if Thursday was an endurance day, you could again pull back on the carb intake, on Wednesday evening, and throughout the day Thursday, assuming Friday was an off or light day.
Capitalize on your transition season, you have the potential to make gains on so many levels. I hope this helps, and if you have questions or need clarifications, please don’t hesitate to contact me.