A Dietitian's Guide to Pre Training Nutrition, Plus Snack ideas to Help you Fuel.

Nutrition is crucial for active people - and what you eat BEFORE training can have a significant impact on your performance in the short, and long term. The goal with pre-training nutrition is to provide your body with enough fuel for you to optimize your training session, while minimizing gastro-intestinal upset. But what is involved in the "fuel" ?

Carbohydrates (CHO) are a key fuel source - but not all carbohydrates are created equal.

Ultimately, all carbohydrates (except fibre) are broken down to simple sugars, but our food choices and the nutrient composition of the overall meal will impact the timeframe that this breakdown occurs.

We have complex carbohydrates, which are often higher in fibre such as oats, potatoes and whole grains - these provide us with a slow, stable amount of energy .

Then we have foods higher in simple carbohydrates, which are lower in fibre and may sometimes be higher in sugar such as white bread, dried fruit, sports drinks etc.

Protein, fibre and fats all act as "buffers" that may also slow the the conversion of carbohydrate to simple sugars. For example, white bread + jam will likely spike our blood sugars faster than whole grain bread + peanut butter.

In addition, there are different types of simple sugars. The two main types that will be briefly discussed here are glucose and fructose.

Glucose is one type of sugar which uses a transporter called SGLT1 - this transporter becomes saturated at 1g/minute.

Fructose on the other hand uses a transporter called GLUT5 and it becomes saturated at 0.6 g/minute. But what does this mean?

This means that choosing carbohydrate sources with both glucose AND fructose may lead to higher rates of carbohydrate oxidation, in other words, more carbohydrates can be used as energy more efficiently. Transporters are like"gates" in a cell - so having both glucose and fructose allows BOTH gates to be open, rather than just one.

It is also important to note that a single carbohydrate source (ex: glucose, fructose, maltose etc) can be oxidized at around 60 g/hour (1). Consuming above this means the leftover CHO may not be used as energy as efficiently and can lead to GI upset. This is why some evidence suggests that having multiple CHO sources may lead to reduced GI upset vs. just one (learn more about this here).

The reason why carbohydrates are getting the spotlight here is because it is much more reliable and efficient as a fuel source compared to protein and fats. The biochemistry with how this plays out is beyond the scope of this article, but below are a few, brief but key points:

• Proteins are built up by different types of amino acids - some amino acids are glucogenic, meaning they can be coverted to glucose, while others are ketogenic, meaning are converted to ketones. However, protein is generally not an effective fuel source - because it takes a lot of energy (calories) to convert it to useable energy. In other words, protein has a high thermic effect (2). Around 25-30% of the kcals from protein are used to digest it and convert it to energy. Amino acids are rarely used as a primary fuel in activity outisde of extreme circumstances (3) such as starvation.

• Fats are easily stored and can provide us with some fuel. But in some cases they are not able to provide fuel as quickly or efficiently as carbohydrates can. This is because fat contains less oxygen than carbohydrates - we can see this when we compare their chemical structures. Because of this, carbohydrates can be oxidized much quicker than fats and be used as an energy source more reliably - especially in high intensity activity (3).

Okay, Carbs are great. but how much do I need?

The amount of carbs you need will depend on the intensity and duration of your training.

You probably won't need a pre-training snack if you're...

• Training for less than 60 minutes

• Training at a low/moderate intensity (ex: light walking, yoga, general low intensity weight training)

You probably should have a pre-training snack if you're...

• Training for 60 minutes or longer

• Training at a higher intensity and/or volume
  

Here are some examples:

If you are going for an hour long walk in mild weather, you probably will not need any additional nutrition aside from your usual meals and snacks.

If you have a 90 minute weight training session including heavy compound lifts, a pre training snack may be helpful.

Meal Timing - WHEN should I eat my pre-training snack?

This will depend on when you're training, and what else you are doing that day. The timing of your meals can have a major effect on the food choices you make.

For general healthy meal planning, we typically want a source of complex carbs, a fruit or vegetable and a protein source. But this can definitely change depending WHEN you're eating.

If you are eating 3+ hours before training, then a standard meal with a source of carbohydrates, protein and a fruit or vegetable should be adequate as our body has time to convert the carbs to energy, and our body has time to digest our meal.

Aim for 1 - 4 g carbohydrate per kg of body weight.

For example, stir fry with rice, protein of choice and vegetables

If you are eating between 2 hours - 90 minutes before training...

We still have some time before training, but our body will need carbs a little more readily available. In addition, we have less time to digest food- so choose easier-to-digest options that are lower in fibre with a moderate amount of fat/protein. 1 - 4 g carbohydrate per kg of body weight is still appropriate, but it may be most realistic to choose closer to 1 - 2 g per kg in order to limit GI upset.

For example, sandwich with two slices of sourdough bread, 1/2 banana sliced and 1 1/2 tbsp peanut butter would provide a decent amount of carbohydrates from the bread and banana, and a moderate amount of fats from the peanut butter.

If you are eating an hour or less before training

We should aim for 0.5 - 1.0 grams of carbohydrate per kg of bodyweight and emphasize fast digesting carbs. Our body needs carbs to be readily available as we do not have as much time! In this scenario, we would want to prioritize low volume foods higher in simple carbohydrates, and we would want to further minimize fats, protein and fibre.

For example, pretzels + dried fruit would provide a high amount of simple carbohydrates in a small volume. Plus, the pretzels would provide some additional sodium, which can be helpful for those with higher sweat rates - especially endurance athletes.

In particular, student athletes or active people with especially busy lifestyles often require low volume, higher carb options pre training. For example, a collegiate rugby player with a full day of classes and a part time job might have lunch at 12:00 noon and practice at 4:00 pm with limited time to eat in between that window. So in this case, they likely need something quick and easy that can be eaten 60 minutes or less prior to their practice.

Below is a Carbohydrate "Cheat Sheet" or quick guide that helps some of my clients in their meal planning.

For example if our rugby player is 74 kg, they might choose a blueberry bagel + 1 tbsp jam before their training session, as this can easily be eaten on the go. This would provide them with approximately 50 grams of carbohydrate (0.68 grams of carbs per kg body weight).

Depending on the length of their practice, it would likely be advantageous to also have some intra-training nutrition (very low volume and/or liquid high carb snack that is easily digested) - but this will be a topic discussed in another blog post, so stay tuned!

Everyone's fuelling needs are different depending on their athletic needs, goals, health needs and lifestyle.

As a registered dietitian, I meet with clients 1 on 1 to help clients optimize their pre-training nutrition whether they are a lifter just starting out at the gym, or powerlifer preparing for their next meet. I still have some spots available, and I would encourage you to check out the services on my website or book a FREE discovery call so we can chat more about your goals!

References

(1) Jeukendrup A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports medicine (Auckland, N.Z.), 44 Suppl 1(Suppl 1), S25–S33. https://doi.org/10.1007/s40279-014-0148-z

(2) Nelms., Sucher. Nutrition Therapy and Pathophysiology. (2015) Cengage Learning

(3) Mul, J. D., Stanford, K. I., Hirshman, M. F., & Goodyear, L. J. (2015). Exercise and Regulation of Carbohydrate Metabolism. Progress in molecular biology and translational science, 135, 17–37. https://doi.org/10.1016/bs.pmbts.2015.07.020