If you are an active person, involved in recreational or competitive sport, what you eat and drink directly affects your performance.

Even a recreational runner covering 20 – 30 km a week will find that they recover better and enjoy running more if they eat a high carbohydrate, low fat diet and boost fluid intake. Many athletes, especially women fear that a high carbohydrate diet will lead to weight gain. But choosing your carbohydrates wisely using knowledge of glycaemic index (GI), last month’s topic, you will avoid fatigue and give your body the best possible performance.

Fuel Lines

The main form of fuel to drive the muscles is called glycogen. It is formed from the breakdown of carbohydrates – starches and sugars – in the small intestine and stored in the muscles and liver. If you want to exercise, train and compete efficiently you need a full tank of muscle glycogen. High intensity exercise depletes glycogen after 30-40 minutes. Low intensity exercise such as walking uses both fat and glycogen as fuel. Fat fuel never runs out but there is a limit to how much glycogen the body can store.  

When muscle glycogen runs out during prolonged exercise or endurance events, the liver’s stores are mobilised provided you ate breakfast to restock the liver after the overnight fast. When liver glycogen runs low the adrenal glands produce a hormone cortisol which breaks down muscle protein to use as energy. Not desirable for an athlete who wants to preserve their muscle mass! So getting enough and the right sort of carbohydrate is critical.

Ready, set…

Eating and drinking before, during and after an event or training session requires a little forward planning and an understanding of digestion. Food takes 2-3 hours to leave the stomach, longer if it is a high fat, concentrated protein meal. It then takes another 2 hours for nutrients to be absorbed into the blood. Some carbohydrate foods are slowly converted to blood glucose, that is they have a low glycaemic index (GI). Others are converted quickly and these have a high GI.

Before exercise

It makes sense to eat a low fat meal 2-3 hours before training or an event and choose carbohydrates which give a sustained release of  glucose into the blood over a longer period. A pre-sport meal of lower GI foods will give a drip release of muscle fuel. A liquid meal also empties faster from the stomach.

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Some suggestions for pre-sport meals and snacks include:

·          Banana smoothie with low fat milk/soy milk

·          Porridge or other wholegrain cereal and fruit

·          Lentil soup and arabic bread

·          Pasta/noodles/rice with vegetables

·          Baked beans on toast

·          Yoghurt and fruit

·          Muffin/crumpet/pancake with honey

Start drinking water at least 20 minutes before the session (aim for 500ml) so you are fully rehydrated.

During exercise

During exercise, blood flow to the intestines reduces by 70-80%. It depends on the length of the training session or event as to whether you choose to eat or not. Research shows that eating some carbohydrates helps to keep blood glucose levels up for use as muscle energy delaying fatigue. For events or training sessions over 90 minutes choose a food you can comfortably digest with a moderate to high GI which release sugar quickly like bananas, jelly beans, muesli bars or a sports drink.

Fluids are critical in delaying fatigue. Thirst is not a good indicator of fluid needs so don’t wait until you are thirsty. Plain water is an excellent sports drink but for events longer than an hour and in hot weather, drink a commercial sports drink. Try drinking 250ml every 15 minutes during exercise. The idea is that larger volumes empty more quickly from the stomach. High sugar drinks such as soft drinks are retained in the stomach for longer making fluid absorption slower therefore they are not recommended during sport.

After exercise

Think of the two hours after exercise as a window period for restocking all your muscle fuel ready for the next session. Carbohydrates can be converted to glycogen faster than normal in the two hours after exercise because muscles are ready to take up glucose. Choose bread, rice, potatoes, pasta, fruit or breakfast cereals. After an exhausting session you may prefer to drink liquid carbohydrates such as a sports drink, fruit juice or smoothie which have the double bonus of replacing your lost fluid. For a quick guide to fluid loss check your weight before and after training . One kilogram of weight lost is equivalent to one litre of fluid.

Sports people do require extra protein depending on the level of intensity of exercise. Exercise damages muscle fibres stimulating the body to repair and regenerate the muscles making them stronger and bigger. Extra protein in the form of a protein supplement drink or extra protein with each meal can help to make up the deficit.

Go!

With a few more events still left on the sports calendar, try boosting your carbohydrate intake with frequent snacks/meals throughout the day and see how it improves your performance. Cutting back on fatty foods and increasing fluid intake might even produce a personal best.

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