Using the same nutrition strategy for all ultra endurance events?

Why different distance, terrains, climates etc require different nutrition strategies.

The world of endurance sports is vast, and so is the science of fuelling it. While there’s a core set of principles that all endurance athletes use for fuelling and hydration, the specific strategy for one event can’t (and shouldn’t) be directly applied to another.

In fact, even the same event can require a different approach depending on the variables at play on the day. Your nutrition plan, much like your training plan, should be adaptable.

I’m going to cover:

• Why we use more fat as fuel in some scenarios and more carbs in others
• The influence of race day variables on nutrition strategy (including night running vs daytime running)
• Examples of how to adapt your nutrition plan

I won’t be deep-diving on hydration, as that is too big a topic to include in this post, I will do a separate post for it.

When do we use fats vs carbs?

One of the big differences in nutrition strategy between events is the percentage of each energy system your body utilises. Contrary to what some people say, we never use any energy system (oxidative, glycolytic, PCr) in isolation; instead, think of it as a continuously varying proportion of each. Those proportions depend on many factors, including intensity and duration of effort.

An ultramarathon can be any distance from 50km to 100 miles to multi-day events. If we focus on the longer end of the spectrum, 100 km+, the intensity is a lot lower than 50km races. The focus for this distance and longer is a steadier, more manageable pace over an extended duration. Because of this, you end up utilising fats, a slower-burning fuel that provides sustained energy, a lot more than you would over shorter, higher intensity-paced distances.

Quick note on fat oxidation: Oxidising fat yields more energy than oxidising carbohydrates. However, it is a less efficient and slower way to get energy than oxidising carbs. That’s why you use different proportions of fat and carbohydrates as fuel in different exercise settings.

That’s not to say you won’t also be utilising a lot of carbs and some protein, because as I said, we are never using one energy system in isolation. The percent of energy you derive from fats and carbs mainly, but also protein, depends on:

• How quickly you need to produce the energy
• How much of that energy source you have available

Once we start running close to 65% Vo2max, we are utilising carbs as energy far more than fat oxidation, which starts to decline.

So how does this influence your nutrition strategy?

50km (flat to rolling elevation)

• higher utilisation of carbs than fats as fuel
• an intra-nutrition strategy should be mainly, if not all, carbs

100 miler

• still high utilisation of carbs, but a higher percent of fat oxidation than 50km
• an intra-nutrition strategy should be mainly carbs, but can also include fats and some protein

Day Vs Night Running

Factors that influence day time vs night time fuelling:

• Temperature/humidity changes between night and day
• Fatigue setting in more (harder to control body temp, affecting sweat rate)
• The risk of gastrointestinal (GI) problems increases significantly when running through the night. The body’s digestive system slows down, making it more difficult to process and absorb large amounts of food

So, how do you tackle night running from a nutrition standpoint?

It can be helpful to reduce your intake to what is necessary during the overnight hours of a race and focus on pushing calories and nutrients more aggressively during the daytime. For some athletes, they will naturally slow during the night, relying more on fat oxidation as fuel, allowing them to reduce hourly carb intake. This can help minimise the risk of nausea, cramping, and other GI issues that can derail a race.

Adapting to the Conditions

It’s not always about comparing different events. Even if you’re doing the same race twice, you’d be wise to adapt your fuelling strategy. A plan you used in a cool, dry climate probably won’t work in humid, hot conditions. The terrain also plays a role; a hilly course demands more from your body than a flat one, affecting your energy needs. Plus, when do you eat? During climbs? Descents? There are a lot of factors, which is what makes working on nutrition in this space all the more fun.

Whilst I can’t write a plan for everyone to use here, because everyone needs their own individual nutrition strategy, I can give you some things to think about.

When creating your fuelling strategy, consider these factors:

• Weather: Temperature and humidity can drastically change your hydration (including electrolyte) needs, as well as carb intake too. In the heat you’ll need more + need to be a lot more adaptable to GI issues as they are for more likely to arise here. Have plan A, B, C, D…
• Intensity: Higher intensity efforts require more quick-access carbohydrates
• Duration: Longer, steadier events can utilise a more varied intake, including fats and proteins - especially on multi-day events
• Terrain: Hilly or technical terrain can increase your caloric expenditure, requiring more fuel
• Logistics: How you will carry your fuel on the course also impacts your choices. What is the impact of temperature on nutrition (does it freeze/become too hard to bite? or melt and go everywhere?)
• Problem-solving: If the worst happens and you’re unable to stomach nutrition, how will you handle this? What anti-nausea, or palate cleansing options have you tried?

The Bottom Line

Ultramarathoners require high volumes of fuel and a dialled-in hydration strategy to perform well. However, because race demands are so different, their nutritional plans must be too. Your fuelling strategy should be a dynamic, not a fixed template. It should evolve with your training and adapt to the unique challenges of each event.

As always, it’s about being strategic to ensure your body is fuelled properly.

Lily x

Sport Nutritionist MSc SENr, Run Coach UESCA, & partial to a jam sandwich.