DietNet - Carbohydrates

Protein, essential fats and micronutrients are primarily used as building materials. Carbohydrate is really nly used as fuel. To get lean, we want to burn up our supplies of excess fat, but to get consistently good performance, we need to give our bodies the right kind of fuel at the right time.

During exercise, we use ATP (adenosine triphosphate) which our bodies can get more easily from muscle glycogen and blood glucose than from stored fat. Muscle glycogen comes from blood glucose, which comes from the carbs that we eat.

You want your muscles to have a good supply of glycogen before you start exercising. Glucose in the blood still needs to be processed before it can be used, while glycogen in the muscles is ready to go. No amount of topping up during your ride will work as well as having a full tank to start with.

As soon as you finish one exercise session, you want to start preparing for the next. So, when you finish a ride, you want to rest, rehydrate and refuel. Your muscle glycogen stores replenish most efficiently straight after exercise - the first 4-6 hours is the best, especially the first 2, then it continues at a slower rate for about 24 hours. Straight after your ride, Michael Colgan recommends 225grams of glucose polymers in liquid form, combined with a little glucose and fructose.

After that, you need to keep your carbohydrate intake steady, to keep your glycogen levels increasing. So it's better to eat your carbs in a series of small meals than in large ones that are widely spaced.

Before your next ride, you need to make sure your levels are topped up. 100-150gms of an easily digested carbohydrate drink about 3 hours beforehand is the optimum.

You're ready for your ride. The question is : what shall I snack on during my ride? If you're only riding for an hour or so, and you've refuelled sufficiently beforehand, you probably don't need anything extra during. Just make sure you've got plenty of water. But if you're off for a longer session, it can be of benefit to keep the carbs trickling in. Colgan recommends 70-90g of a drink containing 5-10% of a solution that contains glucose polymers or glucose, plus a little fructose. Drink this at a rate of about 1 litre per hour.

Once again, experts differ. Training intensity and duration, as well as differences in your biochemical makeup, determine your carbohydrate requirements. The following table taken from "Optimum Sports Nutrition" by Michael Colgan gives a rough guide to the grams of carbohydrate you might need :

Bodyweight	Amount of training (hours per day)
kg	2	3	4	5	6	7
40	200	300	400	500	600	700
50	300	400	500	600	700	800
60	400	500	600	700	800	900
70	500	600	700	800	900	1000
80	600	700	800	900	1000	1100
90	700	800	900	1000	1100	1200
100	800	900	1000	1100	1200	1300
110	900	1000	1100	1200	1300	1400
120	1000	1100	1200	1300	1400	1500

This allows for a small amount of overfeeding - if you start putting on weight, reduce this. If you are doing very high intensity exercise, you might need to increase this allowance. Let's look at our 80kg cyclist from the protein page. Riding for 2 hours a day, he'd need approx 600gms of carbs, riding for 4 hours he'd need approx 700gms.

Barry Sears (the Zone) recommends a lower level of carbohydrate. Work out your protein requirement, then add a third on to get your carbohydrate requirement. Our 80kg man cyclist with 20% body fat needed 112gms of protein - his carbo allowance would be about 150gms. Our leaner cyclist who needed 120gms protein, would need 160gms. This is vastly different from Colgan's recommendation for two reasons - the Zone has a higher % of fat intake, and it is reputed to allow you to burn stored fat more efficiently, which reduces your calorific needs.

Peter D'adamo (Eat Right For Your Blood Type) recommends different ratios for each blood type. His rough guidelines are 72% for A, 60% for AB, 56% for B, and 38% for O types. The metabolic diets range from minimal carbs for extreme Hunter-Gatherers to high carb for extreme Agriculturists. Traditional nutritionists and naturopaths tend to favour high carb diets.

You've already decided whose protein advice you're going to take, so stick with that expert and see how it goes. The acid test is how you feel, how well you ride and how lean you get. Give it a bit of time, as your body takes time to adjust to a new routine. If you don't get an improvement in performance, have a rethink.

The best kinds of carbohydrates are those that release sugar into your system at a steady rate. Dr David Jenkins developed the Glycaemic Index to help diabetics control their sugar levels. The GI of a food measures how quickly and how much it increases your blood sugar level. If the level goes up too much or too quickly, you get that "sugar rush" high, but then your body pumps out insulin to balance out the sugar & your energy levels drop again. Proteins and low GI carbs will help keep your blood sugar levels steadily within the right range.

So how do you know what foods are low GI? Here is a table showing a sampling of common foods. This listing uses glucose as the "standard" food with a factor of 100. (On the links page, there is a site will give you a much more comprehensive listing. It uses white bread as a standard, however. To convert the factors to the same scale as the table below, x by 0.7)

Low GI Foods (below 55)	Medium GI Foods (55-70)	High GI Foods (over 70)
Cereals
All Bran - 30	Vita Brits - 61	Weet-bix - 75
Porridge - 42	Nutrigrain - 66	Cornflakes - 77
Sultana Bran - 52	Sustain - 68	Rice bubbles - 89
Grains/Pastas
Egg fettuccine - 32	Basmati rice - 58	Brown rice - 76
Bulgur wheat - 48	Pizza - 60 (av)	Sunbrown quick rice - 80
Buckwheat - 54	Taco shells - 68	Calrose rice - 83
Breads/Crackers
Mixed grain bread - 45 (av)	Pita bread - 57	Wholemeal bread - 77
Oat bran bread - 47 (av)	Ryvita - 69	Rice cakes - 77
Pumpernickel (rye) bread - 50	White bread - 70	Water crackers - 78
Legumes
Kidney beans - 27 (av)
Lentils - 29 (av)
Chick peas - 33 (av)
Baked beans - 48 (av)
Vegetables
Green peas - 48	Sweet corn - 55	Pumpkin - 75
Carrots - 49	New potato - 62 (av)	Baked potato - 85 (av)
Yam - 51	Beetroot - 64	Parsnip - 97
Sweet potato - 54
Fruit
Cherries - 22	Sultanas - 56	Fruit leather - 70
Grapefruit - 25	Rock melon - 65	Watermelon - 72
Peach - 28 (av)	Pineapple - 66
Apple or pear - 36 (av)
Grapes - 43
Kiwifruit - 52
Banana - 53 (av) - note that ripe bananas have a much higher GI than starchy ones

You also want carbs that are high in micronutrients. So make sure a high proportion of your carbs come from fruit, vegetables, unrefined grains and legumes. The more vitamins and minerals you get in your food, the less likely you are to need a supplement. If you are committed to health, you might like to try eating only whole foods and no refined carbohydrates.

If you are following a metabolic or blood type diet, consult the detailed lists for the specific carbs that will suit you best.

For a run-down on good carbo drinks and sports bars, see the sports bars page. Note that if you are trying out the whole food plan, most snack or convenience food, including sports products, do contain some refined carbs.

No, it's not as simple as just hogging down a big plate of pasta the night before a big race. I'm sorry to tell you that won't work. Carbo loading actually starts 5-6 days before your event. (NB : We're specifically talking tactics for endurance athletes here, strength athletes would use the same principles, but slightly different tactics)

In the first stage, you need to deplete the store of glycogen currently in your muscles. This is necessary to stimulate the enzyme which enables you to store glycogen. Then when you start to reload, you can replenish to a greater extent than before. So to deplete your stores, on days 5-4 before the event, you reduce your carb intake to about 40% of your daily calories and start tapering off the intensity of your training.

This system is muscle specific, which means that if you only work your leg muscles during this stage, you will only deplete & subsequently rebuild glycogen stores in your leg muscles. But you want to have as much glycogen as possible stored in all of your muscles, even the ones you won't be directly using.

Michael Colgan recommends high duration, low intensity exercise covering as wide a range of movements as possible. High intensity is not a good idea this close to competition, as it causes muscle soreness and has a higher risk of injury. On day 5, do light intensity exercise to near exhaustion. On day 4, do a light session 30-60 mins max.

Now for the loading stage. Increase your water intake by 50% during this phase, as glycogen needs lots of water to store it, and keep your fats to a minimum of essential fats. On Day 3, you do another session of exhaustive exercise, which includes resistance training, followed immediately by a 200gm serving of a glucose polymer drink. Then eat 100grams of carbohydrate foods every 1-2 hours, up to 1200 grams in the first 24 hours.

Day 2, do light intensity exercise (30 mins max), eat your normal amount of calories, with 75% coming from carbs. Day 1 before competition is the same, except your exercise is 15-30 mins max. Keep spacing your carbs out through the day in small meals. Resist the temptation to do no exercise the last couple of days. Keep your system moving and do a little.

On the day of competition, have about 200gms of a carb drink 1-3 hours prior to exercise and keep your fluid intake up till about half an hour before.

Carbo loading isn't going to enable you to go harder, it's purpose is to help you go for a little bit longer at the same pace. So it's best suited to events which are over 2 hours long. Anything less than that, you won't need the extra and you'll be carrying extra weight in your muscles.

If you're interested in trying this out, I recommend reading the Carbo Loading chapter in Michael Colgan's book "Optimum Sports Nutrition" to get more details.