Last time, we talked about macronutrients and the importance for balance in general health as well as performance. I hope that’s what everyone took out of it, at least. At the end of the day, balance is key and if there are major swings to focus on one macronutrient, the swing really should be short term and recognized that it may not be a sustainable option for long term (years). At the end of that discussion, I mentioned where I would like to take that conversation. One of the areas included what the definitions of diets actually contained and why the lack of continuity can blur the lines between what we think we are doing and what we actually are. So, today I’d like to explore an article from Burke, et al. (2018) that serves as a guide to understanding diet and exercise strategies. This entire article will be in reference to this article. I will share the link at the bottom of this post!
Let me first discuss that I am moving beyond general strategies here for overall health and talking mainly about running performance and adaptation to training.
High CHO diet
This is what we traditionally think of when we talk about endurance athletes. However, there is no clear definition of what this actually is, other than it is considered a daily diet. Definitions of a high CHO diet range from anything over 50% CHO, 60-70% CHO, 500-600g of CHO per day, or 7-10g/kg of body weight! The underlying premise is that all endurance athletes have a daily need for high amounts of fuel and these are met by high CHO intakes to support hard training. Overall, it’s not recommended to be using in isolation because it’s a poor correlation with muscle fuel needs for training.
Very interesting, huh? If you take anything from this diet is that it’s broad and based off the original research done in the 1960’s. So, this would really be seen as the starting point for endurance athletes. Don’t take away from this that CHO is not needed in larger amounts, but rather that there’s more info needed on an individual basis. Things like- type of exercise, volume, intensity, etc.
It goes back to what you have heard me say before- “Eat to your daily needs.”
Luckily, there’s been a number of updates to that original research that we can build from.
High CHO availability:
CHO spread across the day and is targeted at optimizing glycogen stores by exogenous supplies to meet the fuel demands of the days training/event. Amount is based on goals of training and body weight. Daily intake from 3-12 grams/kg of BW. Basically, we are going to make every run a focus for providing carbs right before, during, and after a run. Then the rest of the day might be a lower overall intake of CHO.
The potential problems are that it may take some guesswork and experimentation on your part to really nail down what works. In really high volume training (2+ sessions/day or 25+ hours per week of training) a person will probably have some training sessions that are low CHO availability.
Peridozed High CHO availability:
Essentially, the strategy as above, but now we decide which ones to make available based on the goals of the training. Each single session may have a different approach based on where you are at in training. So, early on, we may make all easy runs and shorter long runs low CHO availability, but keep high intensity SOS days a high CHO available day. Then, the closer we get, all SOS days may be high CHO available and keep shorter easy days at a low CHO availability. Two studies shown this to show performance improvements, but subsequent competitor studies have not been able to replicate.
Nonketogenic low CHO/high fat:
CHO availability is chronically (up to months) below muscle needs so that adaptations occur to promote fat oxidation. However, it is high enough to avoid ketosis. Typical: 15-20% CHO, 15-20% protein, and 60-65% fat daily intake. Or, CHO can be less than 2.5 grams/kg of BW. One important factor here is that this in combination with a moderate endurance program of less than 5 hours per week. I think that last sentence is pretty key to this! In context- It has been shown that this can up to double rates of fat oxidation, but this has not been shown to be in association with endurance performance overall.
I think there are some very important aspects to look at with this. The first is that there’s no doubt that it can increase fat oxidation and thus probably improve overall body composition. This alone will probably improve endurance performance.
If you weighed 200 pounds and lost 25 pounds of non excess fat, then yes, you will run faster.
However, this is only going to be true up to a point. Also, the amount and intensity of exercise you should be doing with this is pretty low- basically meeting the AHA guidelines for everyday health. I just think you are limited with the situations where this will be successful- especially long term.
A person severely restricts their CHO intake to less than 5% CHO (or 50 g/day), while protein is 15-20% and fat is 75-80% of daily intake. The basic premise is that this type of diet will produce very high rates of fat oxidation within 5 days to 2 weeks. However, extreme fatigue can occur for the first 3 weeks. Overall, exercise seems to be sustainable up to about 75% VO2max, but higher intensity exercise is not tolerated well, if at all. Another factor involved is that the severe restriction of food minimizes nutrient density and variety.
Thinking about the exercise tolerated makes sense. When we discussed macro nutrients, we talked about the body’s back up is to make glucose out of non glucose sources (both fat and protein), but it’s extra steps and it’s slow. The glycogen and glucose required for higher intensity exercise simply can’t be met with these back up mechanisms. I think it goes back to the level of athlete and their desired goal/outcome.
To wrap up, this is all pretty interesting.
For one, the body is really good at making due with what is being provided to it. Also, I think that what works for a lower level athlete isn’t particularly going to work for a higher level athlete. I am referring to both ability and amount of training.
Third, I think it’s important to note that these long term “diets” aren’t really suitable for more than a short period of time.
For instance, a high carb diet might only really be needed for a few days before a marathon. Meanwhile, a LCHF diet may be exactly what an overweight runner needs to shed some weight before starting a training plan and then can eat a more balanced diet. Lastly, what’s interesting in these diets is that the two main variables are fat and CHO. Why not change the amount of protein? For most endurance athletes, I would almost say that you keep CHO at 50-55%, fat at 15% and then protein at 30%. I’d have to work the numbers based on grams per kg of BW, but who knows? I mean, we know CHO needs are slightly higher, but so are protein needs. If we boost protein a little, we can maintain or build muscle during hard training, have a place to store glycogen, and we still change our body composition for the better. Ah well, maybe another time!
So next time, I think we continue on with the article I referenced and look at the more short term strategies and sequences for workouts and tapering (loading). I believe that propels us more into the idea that our “diet” really can shift from day to day. While one day may require a lot of CHO to replace what we utilized, another might not require as much. All in all, I think we are starting to paint the picture that from 10,000 feet, saying calories in, calories out is fine. However, as we zoom in, there’s more to it than that. Until next time!