What you should eat

Cross country; photo by David Knight

Cross country

One of the pleasures of being a runner is that you can eat and drink considerably more than if you have a sedentary lifestyle, and still feel healthy and avoid putting on weight.

Running enables you to escape from the constant hunger, self-denial and self-loathing of dieting, and instead enables you to eat a wide variety of foods more or less as you please.

Nutrition is the third most important determinant of your running performance, after genetics and training.  If you want to be a good runner, you have to eat and drink the right things.  This chapter is about the food and drink you need to maintain a healthy body; the next chapter is about how you should eat and drink before, during and after running.

The main rule for a balanced diet for a typical healthy adult is to eat from a wide range of unprocessed foods.  If you do this, you will not go far wrong. There are several good books about nutrition for athletes which you should read if you want more detail, or if you have special needs (for example, if you are vegetarian or allergic to particular foods). [i] This chapter introduces the key principles for runners.

The main nutrients

The main nutrients for human beings are carbohydrates, fats, protein and water.


Carbohydrates are mainly used for energy. Foods that are high in carbohydrate include potatoes, pasta, rice, bread, fruit, cereals, pulses and anything sugary.

Carbohydrates vary in the complexity of their chemical structure, which in turn affects how quickly they are absorbed into your bloodstream.  Scientists have developed the Glycaemic Index (GI) which ranks foods according to their immediate effect on blood sugar levels. For example, apples have a GI of 38, which means that eating an apple gives you about 38% of the increase in blood sugar that you would get from eating pure glucose.

Table 6.1 High, medium & low glycaemic index foods

High GI foods Moderate GI foods Low GI foods
Food GI Food GI Food GI
Glucose 100 All bran 42 Chick peas 33
Cornflakes 84 Muesli 56 Green lentils 30
Weetabix 69 Buckwheat 54 Red lentils 26
Brown rice 76 Basmati rice 58 Soya beans 18
White rice 87 Spaghetti 41 Kidney beans 27
Bagel 72 Muffin 44 Apples 38
Baguette 95 Carrots 49 Pears 38
Parsnip 97 Peas 48 Plums 39
Baked potato 85 Baked beans 48 Peanuts 14
Raisins 64 Banana 55 Milk 27
Mars bar 68 Orange 44 Yoghurt 33

The glycaemic index was originally developed to help diabetics to manage their blood sugar, but it is becoming more widely recognised as a tool for healthy eating.  You will need to look at the GI of the meal as a whole (which you can estimate by a weighted average of the GI of the main components).

Generally, you should eat low-GI meals, because these don’t lead to such large variations in your blood sugar and insulin levels. Big swings in your blood sugar can lead to higher levels of body fat, reduced immunity from infection, mood swings and stress, and impaired storage of energy by muscles.

However, high GI foods are very useful when need energy quickly, such as immediately before, during and after exercise (see Chapter 7).


Fats are found in oily food, especially animal products, and food cooked in oils.   Fats vary in their chemical structure, which in turn makes a difference to how they are handled by the human body and their impact on health.  Some fats are harmful, and some are essential for health.

Table 6.2 Types of fat and their health implications

Type of fat Health implications Sources
Saturated Heart disease, increase in cholesterol. Butter, lard, cheese, animal fats.  Biscuits, cakes, pastry.  Palm oil & coconut oil
Monounsaturated Good for you.  Can reduce harmful cholesterol. Olive, rapeseed, groundnut, hazelnut, almond oils. Avocados, olives, nuts, seeds.
Polyunsaturated Can reduce both good and harmful cholesterol. Most vegetable oils and oily fish.
The following fatty acids are specific types of polyunsaturated fat:
Omega 3
essential fatty acids
Health of blood and blood vessels. Reduced heart disease, lower blood pressure. Oily fish (e.g. mackerel, fresh tuna, salmon, sardines).  Linseed (flax), pumpkin seeds, walnuts, rapeseed oil, soyabeans.
Omega 6
essential fatty acids
Health of cell membranes. (But can reduce good cholesterol; high intake may be cancer risk) Vegetable oils, polyunsaturated margarine.

In general, many people in western societies eat more fat than they should; and too much of it is harmful saturated fats. You should be getting around 15-25% of your daily calories from fat, instead of an average of over 40% in Britain.  But you should not try to cut fats out of your diet altogether.  Try to get most of your fats from mono-unsaturated fats, such as olive oil, nuts and avocados; and ensure that you have sufficient essential fatty acids, which you get from oily fish and seeds.


Proteins are the building blocks of the human body.  About 20% of your body weight is protein.  It is mainly needed for growth and repair of body tissues, though it can also be used as fuel for energy.  It also plays an important role in the health of your blood system.

The protein you eat is broken down into amino acids, and then recombined to make suitable human proteins.  There are 20 amino acids, of which 12 can be manufactured in the body; but 8 of them, called essential amino acids, cannot, and they must be obtained from what you eat.

Some foods contain all eight essential amino acids – these include dairy products, eggs, meat, fish, and soya.  Other foods such as cereals, pulses and nuts have some, but not all, of the essential amino acids and must be eaten in the right combinations to ensure the body has all the components it needs.  Vegetarians, and anyone else who does not eat much meat, should ensure that they combine foods from two or more of the following four categories:

  • pulses (beans, lentils, peas)
  • grains (bread, pasta, rice, cereals, corn, rye)
  • nuts and seeds (peanuts, sunflower seeds, pumpkin seeds)
  • quorn, tofu and soya products (soya milk, tofu, tempeh, etc)

For example, baked beans on toast is an excellent combination which provides all the essential amino acids.

If you exercise regularly, and especially if you do strength training, you need a bit more protein than if you are sedentary, to enable you to rebuild and repair muscles.    The current recommended daily intake of protein for a sedentary person is 0.75g of protein a day for every kilogram of body weight; whereas people who exercise need around twice this (1.25g to 1.75g) amount of protein a day for every kilogram of body weight.[ii]

Table 6.3: Protein intake

Lifestyle Grammes

Per day per kg

Example for 60kg person Example for 80kg person
Sedentary 0.75 45g / day 60g / day
Endurance runner 1.3 78g / day 104g / day
Strength athlete 1.6 96g / day 128g / day

You can safely eat more protein than this calculation implies, but once your body has used the protein it needs, the extra protein will be burned as energy.  (It is a common myth that eating more protein than this will somehow stimulate better or more muscle formation.)

Eating a balanced diet

Your energy intake should come from a mixture of carbohydrates, fats and protein, made up roughly as follows:

  • 15-25% of calories from fat
  • 60-70% of calories from carbohydrates
  • 15-25% of calories from protein.

From these broad proportions, an estimate of your overall energy needs (see below) and the amount of protein you need, you can estimate the amount of carbohydrate, fat and protein you should have in your diet.

You can do this calculation for your own body weight and calorie intake here on the Running for Fitness website.

However, you should beware of the fact that the different types of food provide different amounts of energy for each gram:

Table 6.4 Energy from different nutrients

Energy source Energy
1g of carbohydrate 4 kcal 17 kJ
1g of fat 9 kcal 38 kJ
1g of protein 4 kcal 17 kJ
1g of alcohol 7 kcal 29 kJ

Because fat has more than twice as many calories per gram as carbohydrates and protein, you should eat a lower proportion of fat by weight of food than the proportion of fat measured by calories provided.  So if fat is 20% of your diet by calories, it should only be 10% of your diet by weight.

Table 6.5 Sample breakdown of carbohydrate, fat and protein


2500 Kilocalories a day 3500 Kilocalories a day
Calories Grams Calories Grams
Carbohydrate 1500 kcal
60 %
2100 kcal
Fat 500 kcal
700 kcal
Protein 500 kcal
700 kcal

Within this basic structure of your nutrient intake, try to eat at least five portions of fruit and vegetables a day (a portion is about 80g – equivalent to an apple or two tomatoes).

Later in this chapter, we shall look at the way you can adjust this calculation if you want to lose weight.

[i] For example The Complete Guide to Sports Nutrition, by Anita Bean (A&C Black).

[ii] Williams, C. and Devlin, J.T. (eds) Food, Nutrition and Performance: An International Scientific Consensus, 1992. Chapman & Hall.

3 Responses to What you should eat

  • Although you mention fruits such in 6.1 above you do not emphasize the importance of eating daily amounts of fruit which is accepted as a vital part of a healthy diet by most reputable nutritionists and indeed the medical profession.Are runners different in that they should emphasize carbohydrate intake and unsaturated foods as part of their regular diets and eat fruit only occasionally save perhaps for raisins ?

  • Danni:

    I attempted to use your calculator for calorie intake on the Running For Fitness website but it only works for people between the ages of 8 and 60. I am 61.

  • aaron:

    hello, i am starting running but work in the construction industry. i am finding it difficult to keep up my strength at work while i am running.

    what would you suggest eating?


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