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You want eat enough carbohydrate to fuel your exercise training, but you don't want too much that it increases body fat.

This nutrition goal highlights a common challenge for athletes and fitness enthusiasts. How do you balance energy requirements for an active lifestyle without expanding your waist line. Here are five practical steps to finding the right balance.

1. Know your body composition goals

The body composition (amounts of body fat and muscle) of elite athletes varies according to the professional requirements of their sport. Here are three broad categories that feature athletes with distinctive body compositions.

• Strength: sumo wrestling, hammer throw, discuss
• Power: sprinting, boxing, wrestling
• Aesthetics: body building, body shaping, gymnastics

If you have just taken up sumo wrestling, there is less need to watch your body fat levels, and therefore any limit on your carbohydrate consumption than if you are four weeks out from your first body shaping contest. For many body builders, severe restriction of pre-contest carbs (less than 100-150g / day) in addition to dietary fat is needed to obtain the low body fat levels that show the muscle definition required to win contests.

A low carbohydrate intake is not healthy in this case, and you don't need to maintain the lowest body fat level all the time. For your sport or activity, establish a maximum and minimum body fat range that you are comfortable with during the season and in the off season.

In the slimming phase aim for only ¼-1/2 kilogram per week body fat loss, so as not to create a calorie deficit that may place a drain on your energy levels. Give yourself enough time to reach your competition shape. Remember, you'll never get there if you don't have the energy to train.

2. Tick off the basics

Before you reduce carbohydrate to trim off weight, audit your consumption of fat and alcohol. Fat has 9 Cal and alcohol 7 Cal per gram whereas carbohydrate has only 4 Cal per gram. Restricting bread and potatoes while still eating cakes, biscuits and chocolate will be counter productive and won't provide the best fuel your body needs.

For an honest assessment of eating habits, keep an accurate eating diary for 3-7 days. Write down everything you eat and drink from the time you wake up until you go to bed. It's easy to leave little snacks out of your diary, so it's best to fill it in as you go, rather than write it all at once at the end of the day.

Your diary will reveal:

• If you are effectively limiting high-fat foods
• Whether you are eating regularly enough to provide all the carbs you need, and
• The triggers that cause you to eat too much or eat when you don't need to

3. Experiment with carbs

According to Australian Sports Dietitian Glenn Cardwell, most adults only eat 150 - 250 grams of carbohydrate a day. This may be enough if you are sedentary, but active people will need more to fuel regular exercise sessions.

Your needs will depend on your sport, training levels, gender and size. The table below shows estimated carbohydrate needs for individuals with different levels of regular activity. Your carbohydrate needs are expressed in grams of carbohydrate for every kilogram of your ideal weight. If you are overweight, your carb needs may be lower than you calculate with your current weight.

Your carbohydrate needs

Carbs (g/kg/day) - Activity level
1 - Very little aerobic activity. What you get on most weight loss programs
2 - Sleeping, watching TV, sitting
3 - Daily chores (the amount most adults eat)
4-5 - A good intake for active people. Walking, moderate exercise, recreational athlete, fitness programs (3-5 hrs / week)
5-7 - Serious amateur athlete, football, netball, bodybuilding, weight training. Medium level exercise (10 hrs / week)
7-9 - Serious professional athlete. Endurance athlete, marathoners (training 20+ hrs /week)
10 - Full-time athletes, ultra-endurance, iron man events, Olympic athletes
Source: Gold Medal Nutrition by Glenn Cardwell (2004)

To determine the amount of carbs you need multiply:

Your weight (kg) x grams of carb/kg target = daily needs

For example: Sue is an amateur triathlete who weighs 65kg trains about 12 hours a week.

Her daily carb needs = 65 kg x 7g carbs/kg/day = 455g

To check if Sue is getting 455g carbs a day she can do the following:

• Accurately write down her average daily food intake, including the serve sizes of all carbohydrate containing foods at breakfast, lunch, dinner and all drinks and snacks. Although there will be daily variations, the average or usual intake is important.
• Use a carbohydrate counter, food table booklet or diet software program to add up how much carbohydrate she gets from her usual diet.
• Compare with the daily target and make any necessary adjustments.

1. More carbs than needed.
Sue's usual diet provides 570g carbohydrate, which is 115g carbs over her estimated needs. If Sue needed to lose body fat, she could cut back on carbs by about 100g a day and see if her body composition changes. She should monitor how she feels in terms of her perceived energy level and hunger as she makes the changes.

A drop in energy level or training performance would suggest she needs the extra 100g carbs. This assessment would be confirmed if Sue reported significantly greater hunger and desire to snack or binge on a lower carb intake.

2. Less carbs than needed.
What if Sue's usual diet provided 290g carbs, which is 165g carbs under her estimated needs? She should first check her energy and hunger levels. If there are no problems here and her training goals are being met, it may mean that Sue can still perform well on a lower carbohydrate intake. I would want to check the rest of her diet has a healthy balance. Any further reduction in carbohydrate to reduce body fat may cause a drop in performance.

At only 290g carbs, Sue could however be missing out on a performance boost that her target carb level may provide. To check she should increase intake for a few weeks to see if her energy level and performance increase.

The aim is to experiment to get the right amount. If eating a greater amount of carbs is difficult, eating and drinking the extra carbs in small regular snacks will help.

4. Go for a dietary check up

If you prefer professional guidance from the outset, or after your own experimentation you are still a little unsure of your diet, you should see a sports dietitian. They have experience with athletes and can let you know if you are on the right track. The expense of a consultation, even just for reassurance is cheaper than any ongoing frustration of being unsure about your diet. You'll also learn other performance enhancing dietary strategies to implement immediately.

5. Change your image

Changing body composition is like stretching a rubber band. Its easy work when you start to pull, but as the rubber becomes more taught you get closer to the maximum stretch. Similarly, you'll only be able to stretch the results you get from diet so far. Cutting back carbs to low levels in an effort to trim down may leave you too low on energy to train well.

For some people, the emotional energy cost of battling body fat levels can also drain motivation. If this is affecting your performance, it may be time to rethink how you approach your chosen activity.

References:
Cardwell, G. (2004) Gold Medal Nutrition, Nutrition Impact
www.glenncardwell.com