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Food and Exercise - Guide and Information

What‘s the best fuel to keep you going when you’re playing sport or working out?

That depends on the activity, how long you do it for and whether or not you want to lose weight, says sports dietitian Dr Trent Watson of the Dietitians Association of Australia.


Although what you eat before and after exercise can make a difference to performance and recovery, the quality of your everyday diet makes a difference too. Regular healthy meals and snacks based on quality carbohydrates (such as whole grains, vegetables and fruit) and lean protein (such as lean meat, poultry, fish, low-fat dairy products, legumes or nuts) can help provide fuel and building blocks for hard-working muscles.

What’s a good pre-workout snack before a 30–45 minute run or bike ride or a cardio class at the gym?

If you’ve eaten regular meals through the day and included healthy snacks based on foods like wholegrains, fresh fruit or low-fat yoghurt, you’re unlikely to need a pre-exercise snack for a session that’s less than an hour, says Watson. Although muscles need sufficient glycogen (the form of carbohydrate that muscles use for fuel), eating a healthy varied diet through the day should be enough to keep up your glycogen stores.

If you haven’t eaten anything for more than three hours prior to exercise, it may be beneficial to have a small carbohydrate-based snack such as fruit, a sandwich, a piece of toast or yoghurt.

What if I’m running, cycling or playing sport at high intensity for more than an hour?

When you exercise at high intensity, such as running or playing a fast game of netball or soccer for more than an hour, you quickly deplete glycogen stores. You can burn up four to five grams of carbohydrate per minute and your muscles can only store enough glycogen for approximately 90 minutes, explains Watson. His advice is to have a healthy carbohydrate-containing snack (such as fruit or yoghurt) 30 minutes to an hour before the exercise session.

You may also need a sports drink containing carbohydrates or a sports gel to replenish glycogen stores if the session lasts for 90 minutes or more. Having a snack based on lean protein and quality carbohydrates (for example, a tuna and salad sandwich on wholegrain bread, or wholegrain cereal with milk or a fruit smoothie) within two hours of an exercise session will leave you less tired and help with muscle repair. This is particularly important for someone who has to exercise or play sport again the next day.

What should I eat if I’m strength training?

That would depend on whether your goal is to bulk up or lose weight, says Watson. To bulk up you need an extra 2,000 kilojoules in lean protein and quality carbohydrate foods over the entire day to help build muscle. You also need a recovery snack that includes a healthy mix of protein and carbohydrate foods such as a milk or fruit smoothie.

If your aim is to lose weight, you don’t need the extra kilojoules but you should have a recovery meal after training — for example, a healthy sandwich of wholegrain bread with reduced-fat cheese and salad or a smoothie.

Although there are commercial protein shakes marketed to help build muscle they’re unlikely to have any more benefit that than a smoothie you make yourself, points out Watson. These shakes and other supplements don’t have any magical muscle building properties. A mix of healthy protein and carbohydrate foods will do the job.

What if I’m in training for a half marathon or a triathlon?

Because this can involve intense training four or five times a week, people who are a healthy weight need to include extra carbohydrates in meals and snacks throughout the day to meet the increased energy demands of training, says Watson. Recovery meals or snacks based on protein and carbohydrate are also important.

How much fluid do I need?

Without sufficient fluid you’ll struggle to get through a run, a gym class or a game of soccer. But how much should you drink?

Thirst isn’t a good guide — by the time you feel thirsty you’re already dehydrated to a level that will affect your performance, says Watson. A better guide to how hydrated you are is the colour of your urine. If it’s clear and pale yellow, you’re hydrated and if it’s not you need to drink more water.

His advice is to make sure you start an exercise session well hydrated and then drink 150–250mls every 20 minutes while you exercise. In hot, humid conditions, you should drink 250mls every 20 minutes. Even if you’re running a long-distance race (such as a 21.2km half marathon in just under two hours) you shouldn’t need more than 1.5 litres of water, providing you were well hydrated to begin with.

How much fluid do I need after exercise?

The only way to really know is to weigh yourself pre- and post-exercise, explains Watson. If you’ve lost one kilogram of body weight you’ll have lost one litre of water. To make up for this you need to drink 150 percent of the fluid lost to account for ongoing fluid loss in your sweat and urine — so if you lost one litre of water you will need to drink 1.5 litres in the four to six hours after exercise to restore your hydration status.

What about sports drinks?

Sports drinks containing carbohydrates are a useful option for high-intensity exercise sessions of 90 minutes or more. Examples of high intensity exercise sessions include running, playing a fast game of netball or soccer, etc.

Is it possible to drink too much?

In extreme cases, some people can develop a condition called hyponatraemia (where they have low-blood sodium concentrations). This causes symptoms similar to dehydration and is potentially life threatening. Although it’s uncommon, it can occur in long endurance events of more than an hour when people drink a lot of water but have small sweat losses, according to the Australian Institute of Sport.

Those most at risk are females with a small build who have long race times — they have small sweat losses, but plenty of time to drink a lot of fluid during the event. Drinking sodium-containing fluids such as sports drinks, and matching fluid intake to sweat loss reduces the risk of hyponatraemia.

Further Information

Dietitians Association of Australia www.daa.asn.au/

Australian Institute of Sport www.ausport.gov.au/ais

Sources

Australian Institute of Sport. Eating before exercise. [online] Bruce, ACT: Australian Sports Commission. c2010 [last updated July 2009, accessed 26 Aug 2010] Available from: http://www.ausport.gov.au/

Australian Institute of Sport. Recovery nutrition. [online] Bruce, ACT: Australian Sports Commission. c2010 [last updated July 2009, accessed 26 Aug 2010] Available from: http://www.ausport.gov.au/

Australian Institute of Sport. Recovery nutrition. [online] Bruce, ACT: Australian Sports Commission. c2010 [last updated July 2009, accessed 26 Aug 2010] Available from: http://www.ausport.gov.au/

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Last published 31 October 2010