The Ultimate Triathlete Diet

The Ultimate Triathlete Diet

Interested in how your diet effects your performance and what you can do about it?

Challenge Tri Camp coached athlete, Katherine, who recently spent two days with us in Mallorca for some 1-2-1 coaching and is coached by Joint Head coach Brent Perkins. Katherine is a degree qualified, Registered Nutritional Therapist. With lots of triathlon experience, having completed numerous 70.3 and 140.6 races, as well as competing for Team GB, Katherine specialises in working with triathletes who are keen to adapt their nutritional intake to get the most from their training and racing. We now work with Katherine and recommend her services to all of our athletes.

Read her blog below:

Is there an ultimate triathlete diet? By the time you have finished reading this you will know the answer.  

Triathletes frequently strive to be the best they can be, not missing a training session, pushing their bodies to the limit on race day looking for improved performance, buying the latest kit but many do not apply the same discipline and focus to their diet.  Perhaps you have tried putting yourself into ketosis, veganism or various versions of intermittent fasting without really understanding why you are doing it, if it is best for you as an individual and still not managed to achieve your ideal race weight or still struggling with an underlying health issue.  This blog may shed a little light on why this may be and how to find out what is best for you.

We are all biochemically unique and what suits one person does not necessarily suit another.  Our genetics, our metabolic flexibility, training programme, stressors from other lifestyle factors such as sleep, diet, work schedule etc all play a role in how our bodies burn fuel and understanding this will help you work out what is best for you.   By ‘fuelling your body’, I am not referring to what you eat during a race and in the few days in the run up to it but what you are eating day-in day-out, 365 days of the year.  Remember that every cell in your bodyis made from what you eat, drink, breathe and touch.   Your diet is critical. 

What should you consider when you are working out the best diet for you?  Here are some key considerations:

  • Your Genetics. By looking at your family, your parents and grandparents and paying attention to your body you may have a good idea of whether you are a fast metaboliser or whether you just need to look at pasta and put on weight.  Now-days, DNA sequencing has opened the door to highly personalised approaches and it is easy to run your DNA profile (through a suitably qualified sports health care professional) to find out if your need, for example, for anti-oxidants, fish oils, protein, vitamin D, is higher than average (even for an athlete) due to inherited genetic variations.  The ultimate information to help providing a personalised diet.
  • Your Metabolic flexibility– this is not only your ability to burn carbohydrates or fat for fuel but your ability to switch between the two sources when required (eg when running the marathon leg of an ironman the ability to tap into fat as a source of fuel is a great bonus relieving pressure on the GI system and reliance on gels). One factor that frequently impairs an athlete’s metabolic flexibility however isdecreasedinsulin sensitivity, in other words reduced ability to use glucose as a source of fuel. This is not uncommon in athletes with reasons typically being chronically elevated cortisol (see below) combined for women with declining oestrogen as they reach menopause years, deprived sleep or simply a poor diet high in refined carbohydrates. Fat metabolism can be impaired by lack of certain substrates such as carnitine (high in animal products), needed to get most fats into the cells where they can be burned for fuel or simply poor cell membrane function.
  • Your Stress Levels – this includes not only your training schedule but your work load, family commitments, personal relationships which all add to your ‘total load’.‘Stress’, both perceived and actual, results in elevated cortisol which releases sugar into the blood streamas from an evolutionary perspective our body thinks it is about to run away from a sabre tooth tiger.  Instead you are probably sitting in your car, getting stressed about the traffic and wondering how you are going to fit that 2 ½ hour turbo session in tonight.  Overtime this can have a detrimental effect on health and is a significant factor why many endurance athletes have elevated fasting blood sugar and insulin resistance, leading to lack of ability to burn carbohydrate efficiently along with other long-term associated health risks. A classic sign of this is abdominal weight gain.   Cortisol is also catabolic –you are literally breaking down muscle by being in a chronically elevated state – individuals who are in this state need higher levels of proteins and nutrients to support the stress pathways (B vitamins, vitamin C and magnesium).
  • Your lifestyle and budget. I am frequently told ‘I don’t have time to cook’.  Cooking does not have to involve recipes and 30 ingredients, what is key is having the food in the fridge in the first place so you have something to throw in a pan or to put straight onto your plate.  

What can you do?

  • Get some blood testing done. Find out if you do have elevated fasting blood glucose and insulin so you can take action if you do and adjust your diet accordingly. Many people think that because they have trained 25 hours a week they can eat what they want, this is not often true without some long-term consequences.  The old adage that you cannot out run a bad diet has a lot of truth to it. 
  • Bin the processed foods.Do this now – no need to wait until the off season!  Eat wholesome, fresh foods that your body is designed to metabolise and buy those with the least chemicals, hormones and pesticides added or sprayed. Get your complex carbohydrates from root vegetables, brown rice, lentils and beans as much as possible.  White rice has a higher impact on blood glucose than pure refined sugar so keep this for appropriately timed race/training nutrition. 
  • Keep your protein levels high (up to 30% of energy intake for an endurance athlete or estimated at 1.2-1.6g/kg, higher for weight loss). Please note this is very hard to do on a vegan diet and beans and pulses do not provide the full spectrum of essential amino-acids without rotation.
  • Eat plenty of brightly coloured fruits and vegetables which are high in antioxidants. Anti-oxidants help to neutralise free radicals that are released in high amounts every time you stress your body.  They are also responsible for part of the training adaptations but too many can cause damage to cells – helping to reduce levels via a diet high in brightly coloured, fresh foods has many benefits.  Post a long/hard training session, a smoothie can be a great way to get these foods into you. 
  • B vitamins and Magnesium –these are vitamins and minerals that are used in large amounts by athletes and need to be consumed in high quantities. It is estimated that over 50% of the population is deficient in magnesiumand that is even before factoring in the high additional needs of endurance training.  Great sources of B vitamins are green leafy vegetables, chicken, turkey and fish whilst magnesium is found in high quantities in nuts, seeds and green leafy vegetables. 
  • Look after your gut.You can eat the best diet possible but if you are not digesting and absorbing properly you will not be getting the benefit of it.  If you have IBS type symptoms, seek advice from a suitably qualified healthcare professional to determine the root cause, such as potential parasites or pathogenic bacteria from all those open water swims that maybe lurking resulting in inflammation, leading to a ‘leaky gut’, potential food intolerances, allergies etc. 
  • Consider adding prebiotic foods such as kefir and sauerkraut to your diet. There is a lot of evidence to show the benefits of probiotics in reducing gut dysfunction in endurance athletes when training and racing, pre-biotics help to feed your gut microflora.  Introduce these foods slowly if you are new to them as they do not always suit everyone. 
  • BE ORGANISED.Consider where you can find those extra 10 minutes to book 2 weekly online orders to ensure a well-stocked fridge. Quality food is expensive but ask yourself how much your new bike cost and have a think about why you are then sacrificing the fuel you put into the engine (your body).  

So, the answer to the question, is there an ultimate triathlete diet, is no.  Is there an ultimate diet for YOU, then answer is, yes.  There are some broad, key guidelines as above that will get you a long way but the fact that we are all biochemically unique is key. Even our own biochemistry will change as we age, as our diet and lifestyle change our metabolism and our genetic expression will change.  Understanding your own body and listening to the messages it gives you (along with some targeted testing) will help you determine the ultimate diet that may just give you that edge you are looking for. 


If you would like more information or would like to chat with Katherine about your individual nutritional requirements, drop us an email at and we will put you in touch.

New to triathlon or done more events than you can remember and looking for support and a team to be apart of, then why not join our race team, its open to all, no matter where you are on your triathlon journey and offers a full range of benefits.  Join our race team.

Select your currency
GBP Pound sterling
EUR Euro
× Available from 08:00 to 18:00