Nutrition Shouldn’t Feel Random: How to Fuel Your Endurance Training With Confidence

Sports Performance Nutritionist Hannah Presswood (pictured left) explains why nutrition needs structure and planning, just like your training routine.

Hannah writes:
"As an endurance athlete, you rely heavily on structure. You follow a training plan, you build your weeks around key sessions, and you understand the value of progressive loading, adaptation, recovery, and consistency. Yet despite this, many athletes continue to treat nutrition as something that sits to the side - important in theory, but not something that requires the same intentional planning as training.

The reality is far less forgiving. Your nutrition directly influences the quality of your training, the sustainability of your weekly load, your long-term health, and the confidence you bring into race day. When it is random, inconsistent, insufficient, or based on guesswork, it doesn’t take long for that to show up in your performance. If you have ever wondered why your legs feel inconsistent from one week to the next, why certain sessions feel harder than expected, or why your recovery seems slow, nutrition is usually the underlying factor.

Is Your Nutrition More Random Than You Realise?

Many athletes unintentionally fall into patterns that seem harmless but limit their performance. Some athletes eat the same foods before and during every session, no matter what it is. Others constantly switch foods depending on what is convenient on the day, without any understanding of the energy content or timing required for optimal training performance. And a large number simply copy what a training partner or elite athlete does!

Each approach has limitations. Eating the same thing for every session ignores how your body’s energy systems shift depending on the intensity and duration of the work you are doing. If you fuel every session the same way, you are inevitably mismatching the energy source with the energy demand.

Constantly changing your food choices without any awareness of the energy content means you are guessing rather than fuelling deliberately. A banana, a Snickers bar and a gel all contain energy, but the amounts differ quite a bit, as does the speed at which they are digested and absorbed. Without understanding those differences, you may be giving your body far less than it needs to perform, or inadvertently creating GI issues.

Copying someone else’s nutrition plan is also no guarantee of success. Physiology, sweat rate, gut tolerance, energy needs, training load, and daily life stress are highly individual. What works for one athlete doesn’t usually work for another.

Understanding How Your Body Produces Energy

To fuel your training deliberately, it helps to understand how your body produces energy at different intensities. At low intensities - typically below about 65% of your maximum heart rate, which is Zone 1-Zone 2, depending on the model being used - your body prefers to oxidise fat for energy. Fat is an excellent long-duration fuel source, but it provides energy slowly. If glucose is available during these sessions, your body will still use it, particularly for brain function (happy brain!) and maintaining movement efficiency, but it does not rely on it exclusively.

As intensity increases, your muscles require a faster, more readily-available source of energy, and this is where glucose becomes essential. Moderate-intensity and high-intensity efforts depend primarily on carbohydrate metabolism because glucose can be converted into usable energy far more quickly than fat can. This is the foundation for why different sessions require different fuelling strategies. An interval session, tempo run or long progression run can’t be fuelled the same way as an easy 40-minute aerobic recovery jog.

Your body’s ability to digest food is also affected by exercise intensity and heat.  The harder your muscles are working, the more oxygenated blood they demand, which directs blood flow away from your digestive system and compromises digestive function.  In hot conditions, your body sends blood to your skin’s surface for cooling, again leaving your digestive system behind.  Trying to consume real foods that require digesting in these conditions means that they will sit in your stomach and cause GI distress, so simple sugars like carb mixes and gels are the better tool for the job. 

When athletes do not understand these differences, the result is usually under fuelling and compromised performance, possibly with some GI issues too. Matching the energy system to the energy source is one of the most fundamental shifts that leads to better consistency and improved training quality.

Hannah Presswood is a Sports Performance Nutritionist and the founder of Real Health Sports Nutrition. She is also a running coach with CMF Running, and an ultra-runner.

Instagram: @real_health.sports_nutrition Website: rhsn.co.nz

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