Nutrition for exercise

How many people follow these diets?

Many individuals exercise at different levels. Recommendations for competitive sport are very specialised but individuals who are 'exercising' rather than training regularly can get all the nutrients they need from following a balanced diet.

As well as carbohydrate for energy and some protein for muscles, vitamins and minerals play an important role in helping your body to function properly. For example, a lack of calcium and magnesium may lead to muscle cramps. A good iron status is important to prevent exercise-induced anaemia. A varied, well-balanced diet that includes all the major food groups will normally ensure an adequate intake of vitamins and minerals (see the eatwell plate).

Energy and nutrition

Depending on the duration and intensity of the exercise you do, your body needs some extra energy. The amount of additional calories required will also vary greatly depending on your body size, age, gender and external factors such as climate, ground or air resistance. For example, male Tour de France cyclists may need up to 7,000 calories a day. However, an average man weighing 70kg would only need about 350 calories when jogging for 30 minutes or 400 calories for swimming (3km/h) for 30 minutes.

Which nutrients are best for providing energy?

Muscles use two main fuels - carbohydrate and fat. Carbohydrates provide rapidly available energy and are therefore the most important energy source for short, intense exercise like sprinting. When exercising at full capacity, the energy requirement is so great and needed so quickly, that only carbohydrates can produce energy fast enough. The body stores limited amounts of carbohydrates - enough for approximately 20 to 30 minutes of moderate exercise. After this, if fat can't be converted to energy during high intensity exercise, the body becomes fatigued.

The body can use fat for supplying energy during longer periods of exercise at a more moderate pace. For those people exercising to help lose weight, it's best to exercise for longer periods at a moderate level to burn fat, ie walking or jogging for longer than 30 minutes.

Whatever the intensity of the exercise, some carbohydrates are always used, and it's important to replenish stores before the next session. It‘s best to top up carbohydrates straight after exercising by eating bananas or drinking high-energy fruit juice-water mixes or sport drinks.

'Carbo-loading'

Athletes preparing for competition sometimes follow a 'carbo-loading' diet, which increases carbohydrate stores and their availability during an event. This can improve sports performance for these athletes and delay the onset of fatigue. Exercise time can be increased by 50 per cent following carbo-loading, which is extremely important for endurance athletes. However, these extreme diets are only suitable for serious athletes and should only be used with advice from a qualified coach or sports nutritionist.

Fluid intake

Fluid intake is extremely important for exercise to prevent dehydration and to compensate for the loss in minerals and carbohydrates. Fluids should be consumed before and during long periods of exercise so choose a drink that you like and that satisfies your needs.

Water is not the best choice. Salts will be lost during sweating and it's important to replace these. The addition of carbohydrate also provides fuel for the muscles, although too many carbohydrates are not good either.

Isotonic drinks can be used for refuelling as they contain an ideal amount of carbohydrates. For rehydrating, hypotonic drinks are ideal as they also provide the body with a lot of fluid. Plan ahead what you will drink during exercise and drink small amounts regularly.

Alcohol should be avoided when exercising and in the days leading up to a period of prolonged exercise as these beverages may lead to dehydration.

Top nutrition tips

• Carefully plan the amount of food and fluids, the number of meals, and the timing of meals (before, during and after exercise) to get the most out of your performance.
• The intensity, duration, mode of exercise, level of conditioning, and how efficiently you move all influence how many calories you'll need.
• Start re-fuelling as soon as you can after training as the muscles' capacity to refuel is greatest over the first hour after training.
• If you have high energy needs don't restrict yourself to traditional mealtimes - eat smaller but more frequent meals, plus several snacks.
• Take a positive interest in food. Take care in planning meals and choosing and preparing food. Enjoy your food!