Baby and You

Triathlon contestants

Louise Sutton explores the important role nutrition plays for endurance activity including the foods and fluids to eat and drink to optimise sports training and performance

More and more of us are taking up cycling, running or triathlon as ways to keep active. Since London 2012, triathlon has seen huge growth with the number of triathlon events increasing by 63 per cent from 2012 to 2016, with about 24 events every week throughout Great Britain*. What nutritional principles should be adopted to support endurance activity and stay healthy too?

Eat a balanced diet

It’s generally agreed that active people don’t require any extra nutrients beyond those they get from eating a balanced, varied diet. The basics of sports nutrition for endurance activity lie in sensible healthy eating. However, choosing the right foods and fluids, when you eat and drink them and the supplements taken (if needed) may be important.

Most people think, nutrition for endurance is all about fuel and especially eating plenty of carbohydrate, but the actual amount needed varies between individuals and the amount and intensity of exercise they are doing. The adjusting of the amount of food and nutrients is an emerging area often called ‘periodisation’. Advice used to be eat large amounts of carbohydrate (up to 70 per cent of total energy) but the science now suggests a more tailored approach, which for some could include periods of lower energy and carbohydrate intake. This is something the media has picked up on with a number of high profile athletes.

In general, people who do regular intense training should make sure they get enough food energy. This includes energy from carbohydrate as well as not forgetting the importance of fluid. If the right amount of food and fluid is eaten and drunk before, during and after exercise, performance can be maximised during exercise and recovery after exercise supported.

For many people water is perfectly fine as a drink of choice

Where do you get energy from?

Energy from food is provided by carbohydrate, protein and fat contained in the food you eat. Carbohydrate is stored in the body as glycogen in the muscles and liver and fat can be stored both in fat cells as well as in the muscles – these are both important energy sources for exercising muscles. The amount of each used depends upon the type, the intensity and the length of your training as well as the desired response from training. Generally, the harder you exercise the more energy is needed, more quickly. When this happens the body tends to use carbohydrate, which is supplied by any sugar in your blood and your glycogen stores. The body has a limited supply of energy available as glycogen so if you are working at very high intensities you are likely to benefit from a diet rich in carbohydrate.


It’s best to mainly eat unrefined starchy sources of carbohydrate e.g. wholegrain bread, brown rice, wholewheat pasta, cereals and potatoes, as part of a healthy diet. However, these can be filling so you may need to ‘top up’ with other sources that are either easier to eat or rapidly absorbed like dried fruit or fruit juice. For many, the best approach is to base all your meals and snacks around starchy carbohydrate foods and eat regularly. Remembering that your glycogen stores are refilled at their quickest in the first half to two hours after exercise, eat a carbohydrate rich snack as soon as possible after training. If you’re struggling to complete training sessions and often feeling tired, your diet may need a review.

Since London 2012, the number of triathlon events has increased by 63 per cent from 2012 to 2016


Active people need more protein than sedentary people. This is because protein is required for building and repairing muscle and plays an important role in how the body responds to exercise.

Protein requirements for people who do endurance sport are 1.2 – 1.7g for every kilogram of body weight a day. For example, a 70kg person would need 84  – 119 grams of protein a day. It’s important to focus on high quality protein foods (such as lean meat, skinless chicken, fish, eggs, pulses and low fat dairy products) at every meal and snack. 

To boost the gains from your training sessions, getting the timing and amount of protein you need is important. Studies show that the addition of 15 – 25g of protein to a post-workout meal or snack can boost glycogen storage, reduce muscle soreness and promote muscle repair. Depending on your goals, if you are training at a high intensity you may benefit from a recovery snack that contains protein.


Fat is the richest source of energy and the main fuel when you do low intensity activity. Fat may contribute more to energy needs when you do slower or lower intensity training and increases as you get fitter (increase your aerobic capacity). Some fat in your diet is essential for good health however, it’s thought many people eat too much, especially in the form of processed foods such as crisps, biscuits and cakes.

The little ‘Extras’

Vitamins and minerals are contained naturally in foods and a healthy balanced and varied diet should provide enough. Vitamin and mineral supplements won’t improve performance, especially if you’re already eating a varied diet containing enough calories. In fact, if some vitamins and minerals (such as iron, zinc and vitamin E) are taken in excessive amounts, they can impair immune function.

Vitamin and mineral supplements won’t improve performance, especially if you’re already eating a varied diet containing enough calories.


For many people water is perfectly fine as a drink of choice, however, if you opt for a sports drink, choose one that contains carbohydrate and electrolytes (particularly sodium). This is especially important if the length of training is over one hour. Carbohydrate will help to keep your energy levels up, whilst the sodium helps your gut absorb it more quickly. ‘Isotonic’ drinks are usually the best choice.

If you experience unpleasant symptoms when you drink during exercise, this could mean you have left it too late and your body is already dehydrated. Sometimes however, it could also mean your choice of drink is too concentrated. When choosing what to drink, choose something you like the taste of because you’re much more likely to drink it.

What about other supplements?

There are many supplements on the market, some appearing to claim highly impressive effects. One with emerging scientific evidence is beetroot juice which, for some, may improve endurance performance. It is rich in nitrate, which appears to improve blood flow to exercising muscles and can, in some situations, help you tolerate exercise better. Research is at an early stage and the precise way that nitrate may be beneficial has not been fully established. It’s thought that people who are less active and do exercise more for leisure get greater improvements than top athletes. If you use beetroot juice be prepared as some people get mild gut discomfort. You may also get pink coloured urine but don’t worry, that’s perfectly harmless!

Eating for endurance activity should not be too tricky. Get the nutrition you need by planning what you are going to eat, when you are going to eat it and how much you are going to eat. If you’re concerned you’re not meeting your nutritional needs, I recommend you seek advice and support from a registered sport and exercise nutritionist. You can find details of a practitioner near you at


References available upon request.

Top tips to optimise endurance performance

• Eat little and often

• Choose a variety of food including foods containing carbohydrate, based on the amount of exercise you do

• Add protein containing foods to meals and snacks

• Aim to stay ‘just ahead of thirst’

• Plan and prepare to fit your eating in around your training

Louise Sutton, Head of Sport and Exercise Nutrition at Leeds Beckett University and consultant nutritionist to the National Race Walking Squad, has advised many elite athletes from a range of sports and was recently awarded the BDA Role of Honour for her contribution to the Sport and Exercise Nutrition Register.


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