Top six triathlon nutrition mistakes

We do not like to focus on the negatives at Fuelin. Rather than calling these mistakes, perhaps we look at them as errors of judgement. These are often the result of a lack of understanding or knowledge. Certainly not the athlete's fault.

One could be excused for making mistakes when there is so much to contend with in the world of triathlon. From course management, training for three separate disciplines, registration completion, to gear maintenance. It is a full-on process. More often than not, nutrition gets put in the wayside and this can be one of the biggest mistakes of all.

I will cover the following items in this article;

Baselines,  carbohydrate and hydration strategy, single macro-nutrient focus, chronic low energy availability and finally, race day plans.

1. Baselines

This is such an important part of any program, not just a nutrition plan. If you do not know where you are starting, how do you know where you are going? Baselines can come in all sorts of forms. These can relate to body mass and body composition with testing such as DXA scans, skinfolds and weight tracking. Food intake baselines can involve questionnaires and a food diary. This can be digital in the form of MyFitnessPal or LoseIt. Both of which sync, automatically with the Fuelin app.

Other baselines could involve “taking a look under the bonnet” and getting thorough blood draw completed. This is to investigate certain markers in the blood that relate to health. This is not to be told that certain foods fit your blood type! That is rubbish. Establishing your baselines in markers such as your iron panel (ferritin, serum iron, total iron binding capacity, ferritin saturation) and vitamin D would all be very sensible for an endurance athlete of any age and any gender. At Fuelin we provide a complete blood panel recommendation to all our athletes. 

2. Carbohydrate intake in training

Carbohydrate intake and overall carbohydrate capacity can be thrown into the baseline topic as well. If you do not understand or know what your carbohydrate capacity is on the bike or run, how can you expect to execute effective training and most certainly, an effective race? 

Practising your bike and run carbohydrate intake during appropriate intensity training sessions (Z3 or race pace or above) of appropriate duration, you can effectively understand the number of carbohydrates that you can consume per hour. This number is purely individualised yet through consistent and persistent practice, this number of carbs can rise and improvements in gastrointestinal complaints can be made. 

Understanding what products work for you, what an athlete can tolerate from taste and product consistency is all part of this process. Hitting carbohydrate intake amounts of 60g/hr, 90g/hr and 120g/hr comes with practice, not hope. Our advice is to begin to practice your race fueling in training so that, come race day, there is no second guessing.

What we do at Fuelin, is guide you on when you should do carbohydrate capacity training, what products to use and the amounts you should be training with. Failing to plan, is planning to fail!

3. Understanding hydration 

In a similar vein to carbohydrate capacity, a failure to fully understand one’s own hydration requirements is all too common in the world of triathlon. Fuelin focuses on educating the athlete through repeated testing of body weight lost during sessions combined with thorough logging of fluid & product intake in order to provide clarity to you. It is only through repeated measurements during multiple sessions of the bike and run at varying intensity (Z1/2 vs Z3+) and at varying temperatures (<30C/85F vs >30C/85F) that you will gain a thorough understanding of your own hydration strategy. Our recent Q&A sessions and articles discussing hydration and sodium requirements are insightful and we encourage you to read and watch them. It is important to understand your own sweat rate to make the correct hydration decisions during training and racing.

4. Single macronutrient focus

If someone is screaming at you that there is a single macronutrient that will make all the difference to your health and performance, walk the other way. It simply is not true and can lead to serious negative consequences in both, health and performance. All three macro-nutrients, protein, fat and carbohydrates all serve important functions in your day-to-day fueling and can also play important roles in your performance fueling. The context of each should be considered in conjunction with what your goals are and what you as an individual require. Protein will be very important for muscle maintenance and recovery along with having a beneficial impact on immune function. Fat is crucial for hormone production, total caloric intake and for lower-intensity sessions that require fueling. This is to assist with metabolic flexibility and fuel utilisation by the body. Finally, carbohydrates will assist total energy requirements, positively impact bone health, and deliver a plethora of micro-nutrients when consumed in the form of vegetables, dairy, pulses and grains. The more processed and higher glycemic forms of carbs will be the fuel of choice for when you are pushing hard and looking to perform at your peak. They will be especially important for race day and in your preparation for your race day during specific trainig sessions. Choosing one macro-nutrient at the expense of another is not advised.

5. Chronic low energy availability 

Consciously reducing energy availability or energy intake at set points in a training program is required in order to lose body mass and more specifically, body fat. Physics determines this through a net deficit of energy when compared to energy expenditure. I did not make that up!
The period of time that this occurs should be planned thoroughly. The quality and relative percentages of each macro-nutrient being consumed should be included in this planning so as to avoid unnecessary lean muscle loss and the potential for sickness and injury to occur.

Unfortunately, when an athlete sees results from caloric restriction or low energy availability (LEA) during periods of training, they often get caught in a downward spiral of wanting to do it more to see a further loss in body weight/fat. This often comes with unexpected negative consequences. Chronic low energy availability can impact both males and females. It can result in impaired bone health, low libido, reduced stress tolerance, poor sleep quality, abnormal menstrual cycle, lean muscle mass loss, low energy and depression. This is known as Relative Energy Deficiency in Sport (RED-S) and is far too common to be dismissed. 

Through optimal nutrition program delivery in line with your coach's training plan, it is possible to cycle through periods of caloric restriction whilst avoiding RED-S if your initial primary goal is an improvement in body composition. It is important to recognise the signs and symptoms of RED-S and LEA. If they do present, please discuss with your nutrition expert, Dr or coach to get help early on.

6. Race day planning.

Finally, the race is upon you and it is apparent that no nutrition plan is in place. Hopefully, if you have practised carbohydrate capacity testing and worked on your sweat rate testing this is not the case, yet sadly, for so many triathletes it is. So much time is spent swimming, biking and running without a thought applied to what will be consumed on race day to fuel an event that will last minimum 2hrs (marathon), all the way through to 15 hours (IM age grouper).  If you are not doing sessions that mimic your race and practising your race fueling and hydration then it can all go wrong, very quickly. We are often asked for race day plans and we purposefully do not do them. Our belief is that the Fuelin program empowers and educates the endurance athlete to build out their own personalized race day plan through consistent and repeated training, fueling, hydrating and testing. In our experience, this is a much better way of approaching a race and far more rewarding for everyone involved.

Feel free to ask questions,

Fueling you,


Scott Tindal
May 6, 2024
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